utrecht summerschool on environmental signalling and abstracts_201… · utrecht summerschool on...

[Faculty of ScienceBiology]

Programme and Book of Abstracts

Graduate school Experimental Plant Sciences

Utrecht Summerschool

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Environmental Signalling

Utrecht, The Netherlands22 - 24 August 2011

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Contents

Sponsors page 6

General Information page 8

Programme page 10

Abstracts – Poster Session page 16 List of Participants page 39

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SPONSORS

We cordially thank all sponsors for their support of this summerschool!


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EPS Summerschool Programme

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Programme

Monday, 22nd of August SIGNALS FROM WITHIN RUPPERT-ROOD

09:00 - 10:00

Arrival and registration

10:00 - 10:15 Sjef Smeekens (Utrecht University, NL)

Welcome and Opening of the Summerschool

10:15 - 11:05

Sean Cutler (University of California, Riverside, USA)

11:05 - 11:55

Ikram Blilou (Utrecht University, NL)

EDUCATORIUM-RESTAURANT

12:00 – 13:15

Lunch

SIGNALS FROM WITHIN RUPPERT-ROOD

13:15 - 14:05

Alain Goossens (VIB Plant Systems Biology, Ghent, Belgium)

14:05 - 14:55

Joost Keurentjes (Wageningen University, NL)

14:55 -15:45

Coffe break/Drinks

SIGNALS FROM THE UNDERGROUND

15:45 - 16:35

Julia Bailey Serres (University of California, Riverside, USA)

16:35 - 17:25

Marcel van der Heijden (Agroscope, Zürich, CH /Utrecht University, NL)


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Tuesday, 23rd of August SIGNALS FROM OUT OF SPACE RUPPERT-ROOD

09:00 - 09:45

Phil Wigge (John Innes Centre, Norwich, UK)

09:45 - 10:30

Elena Baena Gonzalez (Inst. Gulbenkian de Ciência, Oeiras, POR)

10:30 - 11:00

Coffee/Tea break

11:00 - 11:45

Salomé Prat (Centro Nacional de Biotecnología, Madrid, ESP)

11:45 – 12-30

Bas Rutjens (Utrecht University, NL/John Innes Centre, UK)

EDUCATORIUM-RESTAURANT

12:30 – 13:45

Lunch

RUPPERT-111, -114, -116 PARALLEL SESSIONS (SELECTED FROM ABSTRACTS)

13:45 - 16:30

Selected presentations - Parallel sessions (Programme see pages 12-13)

BOTANICAL GARDENS

16:30 - 19:00

Poster viewing and drinks in Botanical Gardens

DINNER PARTY IN BOTANICAL GARDENS (19:00 - 00:00)


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Tuesday, 23rd of August SELECTED PRESENTATIONS Session 1.1 “Jasmonic Acid Signaling” RUPPERT-111

13:45 - 14:05

Anjali Ralhan (Universität Göttingen, GER)

COI1 but not plant-derived JA is required for Verticillium longisporum propagation and subsequent disease symptoms in Arabidopsis thaliana.

14:05- 14:25

T. Menzel (Wageningen UR, NL)

Transcriptomic response of Lima bean plants to herbivory after low dose phytohormone application

14:25- 14:45 Dieuwertje van der Does (Utrecht University, NL)

Suppression of jasmonate signaling by salicylic acid acts downstream of SCFCOI1 and targets GCC-box promoter motifs in Arabidopsis

Session 1.2 “Plant Physiology” RUPPERT-114

13:45 - 14:05

Mieke de Wit (Utrecht University, NL)

Competition for light severely hampers defence signalling in Arabidopsis thaliana

14:05- 14:25

Alexander Meier (Universität Göttingen, GER)

Posttranscriptional regulation of the GRAS protein SCARECROW-like 14 (SCL14) during plant detoxification processes

14:25- 14:45 Allison Strohm (University of Wisconsin, USA)

The TOC Complex May Mediate the Plastid Localization of a Gravity Signal Transducer in Arabidopsis

Session 1.3 “Plant-Fungus Interactions” RUPPERT-116

13:45 - 14:05

Pieter Timmermans (KU Leuven, BEL)

Study of the interaction between Rhizoctonia solani and Arabidopsis thaliana via a transcriptomic approach.

14:05- 14:25

Helen Kinns (Rothamsted Research, Harpenden, UK)

Exploring basal defence responses to Fusarium culmorum and F. graminearum infection in Arabidopsis floral tissue

14:25- 14:45

Lisong Ma (University of Amsterdam, NL)

Localization and Function of Effector AVR2 from Fusarium oxysporum.

14:45 – 15:15

Drinks


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Tuesday, 23rd of August SELECTED PRESENTATIONS - CONTINUED Session 2.1 “Expressional Responses to Environmental Cues” RUPPERT-111

15:15 - 15:35

Anna Joe (University of Nebraska-Lincoln, USA)

Pseudomonas syringae Type III Effector, HopU1, targets RNA binding proteins and suppresses the plant innate immune system

15:35 – 15:55

Neena Ratnakaran (Universität Göttingen, GER)

Functional analysis of stress-inducible NAC factors in Arabidopsis thaliana

15:55 - 16:15 Julia Wind (Utrecht University, NL)

Fructose sensitivity is suppressed in Arabidopsis by the transcription factor ANAC089 lacking the membrane-bound domain

Session 2.2 “Technologies in Plant Signaling” RUPPERT-114

15:15 - 15:35 Hans van Veen (Utrecht University, NL)

Regulation of contrasting flooding responses: a RNA-seq approach in two Rumex species

15:35 – 15:55 Joanna Schneider-Pizon (VIB Ghent, BEL)

A proteomics approach to brassinosteroid signalling Glycogen Synthase Kinase3 (GSK3)-like kinases in Arabidopsis

15:55 - 16:15

Astrid Nagels Durand (Ghent University, BEL)

Specific identification of E3 ubiquitin-ligase targets

Session 2.3 “Genetics of Plant Immunity RUPPERT-116

15:15 - 15:35

Nora Peine (MPI for Plant Breeding Research, GER)

Connecting pathogen perception to transcriptional reprogramming in plant immune responses

15:35 – 15:55 Dmitry Lapin (Utrecht University, NL)

Genetic mapping of broad resistance to downy mildew in Arabidopsis C24

15:55 - 16:15

Laura Masini (The Sainsbury Laboratory, Norwich, UK)

A novel high-throughput forward-genetic screen to identify key components leading to PAMP-induced resistance to bacteria


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Wednesday, 24th of August SIGNALS FROM ENEMIES RUPPERT-ROOD

09:00 - 09:45

Fumi Katagiri (University of Minnesota, St. Paul, USA)

09:45 - 10:30

James Alfano (University of Nebraska, Lincoln, USA)

10:30 - 11:00

Coffee/Tea break

11:00 - 11:45

Jurriaan Ton (Rothamsted Research Institute, Harpenden, UK)

11:45 - 12:30

Steven Spoel (University of Edinburgh, UK)

12:30 – 13:45

Lunch

SIGNALS FROM NEIGHBOURS RUPPERT-ROOD

13:45 - 14:30

Carlos Ballaré (University of Buenos Aires, Argentina)

CLOSING LECTURE

RUPPERT-ROOD

14:30 - 15:15

Rob Dirks (RijkZwaan, De Lier, NL)

15:15

Sjef Smeekens (Utrecht University, NL)

Closing and drinks

EPS Summerschool Posters

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Abstracts – Poster Session (in alphabetical order of first author)

1. Plant basal resistance: Genetics, Biochemistry, & Impacts on plant‐biotic interactions. Shakoor Ahmad1, 2, Nathalie Veyrat3, Ruth Gordon‐Weeks1, Andrew Neil1, Corné Pieterse 2, and Jurriaan Ton1, 4. 1 Centre for Sustainable Pest and Disease Management, Rothamsted Research, UK;

2 Institute of Environmental

Biology, Utrecht University, The Netherlands; 3 FARCE, University of Neuchâtel, Neuchâtel, Switzerland; 4

Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK

Basal resistance depends on a wide range of inducible defences that become active upon pathogen/insect attack. We have examined different aspects of basal defence in Arabidopsis and maize. It is commonly assumed that the speed and intensity of these inducible defences determines the effectiveness of basal resistance. To examine this further, we explored natural variation among Arabidopsis accession in defence responsiveness to pathogen‐associated molecular patterns (PAMPs) and the defence hormone salicylic acid (SA). Quantitative trait loci (QTL) analysis of this natural variation identified loci regulating the sensitivity of these inducible defences. One QTL controlling SA responsiveness was found to contribute to basal resistance against Pseudomonas syringae pv. tomato. Next, we investigated the contribution of benzoxazinoids (BXs) in basal resistance of maize, using maize bx1 mutant lines impaired in the first step of BX biosynthesis. Compared to wild‐type lines, bx1 lines displayed reduced penetration resistance against aphids and fungus. Furthermore, infestation of wild‐type plants by aphids and fungi stimulated the conversion of DIMBOA‐glucoside into HDMBOA‐glucoside and DIMBOA, which was most pronounced in the apoplast of challenged tissues and preceded tissue damage or symptom development. Upon further investigation of wild‐type and bx1 mutant lines, we observed significantly reduced callose deposition in bx1 plants after PAMP treatment. Furthermore, DIMBOA infiltration of the apoplast mimicked PAMP‐induced callose. Hence, DIMBOA acts as a regulatory signal in aboveground cell wall defence of maize. BXs have also been reported to act as allelopathic signals in the rhizosphere. Analysis of root exudates revealed that DIMBOA is the dominant BX in root exudates of maize. To investigate the impact of BXs on plant‐beneficial rhizobacteria, we monitored the impact of BXs on root colonisation by GFP‐expressing Pseudomonas putida KT2440. Wild‐type plants allowed more bacterial colonization than bx1 plants, suggesting that BXs are involved in recruitment of beneficial rhizobacteria.

2. Tissue specific responses of tomato plants to infection with Botrytis cinerea Tom Beyers1, Janick Mathys1, Mieke Vanhaecke1, Rudi Aerts2, Monica Höfte3 and Bruno Cammue1 and Barbara De Coninck1 1 Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Belgium; 2 Research group Sustainable Crop Protection, KH Kempen, Belgium; 3 Laboratory of Phytopathology, Ghent University, Belgium

Botrytis cinerea is one of the most devastating fungal pathogens in heated tomato greenhouses. Very often infection sites are found on stem wounds, which are created during leaf pruning. The susceptibility of those wounds is, however, strongly dependent on their appearance. Smooth stem wounds, formed when the entire leaf was properly removed, show high levels of resistance to infection by B. cinerea. On the contrary, petiole stub wounds, formed when a part of the petiole is left on the stem, are very susceptible. Preliminary data suggest that the inducible defence response at the site of infection is the basis for the resistance displayed by smooth stem wounds. Stem wound


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inoculation experiments with B. cinerea on tomato mutants deficient in methyl jasmonate, ethylene and abscisic acid signalling, known to be important in the B. cinerea‐tomato interaction on leaves were performed. Several observations were made during those infection tests. At first none of the mutants showed increased symptom development on smooth wounds compared to wild‐type plants. Secondly, significant differences in susceptibility between stem and leaf tissues were observed. In addition the rejection of the petiole stub after inoculation with B. cinerea occurs differently between the mutants. Furthermore, the deposition of phenolics in cell walls of smooth stem wounds and petiole stubs, was microscopically studied since fortification of the cell wall plays an important role upon B. cinerea inoculation. Results of both the mutant analysis as well as the microscopic data will be discussed.

3. Exploring natural genetic variation of plant responses to combinatorial stresses Silvia Coolen, Hans van Pelt, Saskia van Wees and Corné Pieterse Plant‐Microbe Interactions, Department of Biology, Utrecht University, The Netherlands

Biotic and abiotic stresses are major components of natural selection in the wild. In nature, plants have to cope with a wide range of biotic and abiotic stress conditions. As plants have co‐evolved with an enormous variety of biotic and abiotic stresses, they harbour a fantastic reservoir of natural adaptive mechanisms to simultaneously cope with multiple stresses that until to date remained unknown or poorly understood. In order to gain new insights into how plants selectively adapt to the combined effect of pathogen infection, insect herbivory, and exposure to drought, we explore the resource of natural adaptive stress responses in Arabidopsis thaliana (Arabidopsis) to simultaneous interactions with multiple stresses. To this end, we analyze the effect of herbivory by caterpillars of Pieris rapae and drought stress on the level of resistance to the necrotrophic fungal pathogen Botrytis cinerea in the HapMap collection of 360 Arabidopsis accessions. This GWA‐360 collection represents a wide variety of globally collected Arabidopsis plants that are genotyped for 250.000 single nucleotide polymorphisms (SNPs), which allows for genome‐wide association mapping and cloning of genes of interest. We found that there is great natural variation in the effect of herbivory and drought stress on the level of B. cinerea resistance. Herbivory by P. rapae caterpillars or drought stress influenced the resistance against B. cinerea in many accessions, either positively or negatively. These data will be used for genome wide association mapping in order to identify novel genes that play a role in the capacity of plants to simultaneously adapt to multiple stresses, ultimately with the goal to utilize this knowledge to provide novel tools for sustainable agriculture and combinatorial stress resistance breeding and apply these tools to crop plants.

4. Expression profiling of lettuce response to Botrytis cinerea infection Kaat De Cremer1, Janick Mathys1, Mieke Vanhaecke1, Bruno Cammue1 and Barbara De Coninck1 1Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20 , 3001

Leuven, Belgium

Lettuce (Lactuca sativa) is the second most important greenhouse crop in Belgium. Its intensive production causes the crop to be susceptible to different pests and diseases caused by bacteria and fungi. Grey mould caused by the necrotrophic fungus Botrytis cinerea is one of the most important diseases that threatens the cultivation of lettuce. To better understand the interaction between this pathogen and its host we opted for a whole‐genome transcriptome profiling strategy. This approach is ideally suited to study the complex overlapping responses of plants to biotic stresses and to reveal how the biological systems are regulated at the transcriptional level. In a first series of preliminary


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experiments we determined the expression levels of known defense‐related genes at different time points after infection, as a basis for defining the timeframe for transcriptome analysis. With respect to the latter we made use of “cross‐hybridization” to Affymetrix oligonucleotide GeneChip microarrays designed for Arabidopsis thaliana, since the classical commercial microarrays are not available for lettuce. Such a “cross‐hybridization” approach on Arabidopsis arrays has been reportedly successful for other plant species. In the present study, we specifically used a genomic DNA‐based probe‐selection strategy to improve the efficiency of detection of differentially expressed lettuce transcripts. Results of this microarray analysis as well as validation by qRT‐PCR will be discussed.

5. “Characterization of novel proteins involved in jasmonate signaling” Amparo Cuéllar Pérez, Laurens Pauwels, Astrid Nagels Durand, Jan Geerinck, Robin Vanden Bossche, Rebecca de Clercq and Alain Goossens. Department of Plant Systems Biology, VIB and Department of Plant Biotechnology and Genetics, Ghent University, Belgium

Jasmonates are ubiquitous plant hormones known to play essential roles in plant defence and development. Recent research efforts led to the discovery of the core module of jasmonate (JA) signalling. It involves bHLH‐type transcription factors, such as MYC2, that regulate JA‐dependent gene expression and that, in the absence of jasmonates, are repressed by the JAZ proteins. To exert their function, JAZ proteins need to recruit co‐repressors, namely NINJA and TOPLESS. Upon JA perception, JAZ proteins are bound by the F‐box protein COI1, which forms part of the SCF E3 ubiquitin ligase complex that triggers JAZ ubiquitination and degradation, which in turn releases the bHLH transcription factors to promote the JA responses. Our research focuses on the identification of novel proteins involved in JA signalling through mapping of the interactome of the core module proteins with techniques such as Tandem Affinity Purification and Yeast Two Hybrid. Several candidate interactors have been selected for further functional characterization. One of the selected proteins is TIFY8, which, like the JAZ proteins, belongs to the TIFY family but differs from them in lacking the domain responsible for interaction with the MYC2‐like bHLH factors and COI1. TIFY8 does, however, interact with NINJA, TIFY family proteins (including the JAZ and PEAPOD proteins) and transcription factors with yet unknown function. Transgenic lines with altered expression of TIFY8 (i.e. knock‐out and overexpression) have been generated but do not show JA‐related phenotypes. Interestingly, based on gene expression arrays, TIFY8 seems to be regulated by salicylic acid rather than by jasmonates, hinting at a possible function in the cross‐talk between these two hormonal signalling pathways.

6. Identification and validation of Key factors of stress tolerance in Arabidopsis thaliana Agyemang Danquah1, Anette Maeh2, Axel de Zelicourt1, Nicolai Frei de Frey1, Stephanie Pateyron1, Jean Colcombet1, Jorg Kudla2, and Heribert Hirt1 1Plant Genomic Research, Unit Unité de Recherche en Génomique Végétale (URGV), France; 2Molekulare Entwicklungsbiologie der Pflanzen, Universität Münster, Germany

Abiotic stress is the principal cause of crop failure worldwide, reducing average yields of most crops by more than 50%. Individually, these stress conditions have been the subject of intense research. However, in the field, a combination of different abiotic stresses cause severe losses and little is known about the mechanisms of acclimation of plants to a combination of stresses. Vital to most


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signaling and adaptation reactions in response to abiotic stresses are complex protein kinase networks that function early and translate environmental cues to regulating downstream transcription factors to orchestrate long‐term responses by functionally coordinating the expression of stress‐responsive genes. To indentify these key factors in stress tolerance, we have performed bioinformatics analysis on existing transcriptomic data on heat, drought and combined heat/drought stresses and have identified several candidate genes. In order to confirm their functions in stress responses, we aim to (a) identify knockout mutants from T‐DNA insertion collections (b) generate over‐expression lines of these genes and phenotype under stresses. Among the putative genes, we found several MAPKKK that we want to investigate further. Yeast two hybrid assays revealed specific interactions of these MAPKKKs with a MAPKK. The possible significances of these interactions in the abiotic stress regulatory network as well as functional implications are discussed.

7. Suppression of jasmonate signaling by salicylic acid acts downstream of SCFCOI1 and targets GCC‐box promoter motifs in Arabidopsis Dieuwertje van der Does1, Antonio Leon‐Reyes1, Annemart Koornneef1, Nicole Rodenburg1, Johan Memelink2, Corné Pieterse1, Saskia van Wees1 1 Plant‐Microbe Interactions, Utrecht University, P.O. Box 800.56, 3508 TB Utrecht, The Netherlands; 2 Institute of Biology, Leiden University, Sylvius Laboratory, P.O. Box 9505 RA, Leiden, The Netherlands The signaling molecules salicylic acid (SA) and jasmonic acid (JA) play major roles in the plant immune signaling network. The SA‐ and JA‐controlled signaling pathways can cross‐communicate leading to a finely tuned plant defense response. In Arabidopsis thaliana, SA suppresses expression of JA‐responsive genes, among which PDF1.2 and VSP2. Here, we aim to unravel how SA exerts its antagonistic effect on JA‐responsive gene expression and at which level in the JA signaling pathway SA is acting. CORONATINE INSENSITIVE 1 (COI1), which is part of the SCFCOI1 complex, is an essential component in the JA signaling pathway. In coi1‐1 mutant plants that overexpress the transcription factor ERF1, expression of PDF1.2 is rescued (Lorenzo et al., 2003: Plant Cell 15: 165‐78). Here we show that SA can still suppress ERF1‐induced PDF1.2 expression in 35S::ERF1/coi1‐1 plants, demonstrating that SA can target the JA signaling pathway downstream of SCFCOI1. ERF1 protein accumulation was not affected by SA in 35S::ERF1‐TAP plants, indicating that the antagonistic effect of SA on ERF1‐mediated gene expression is not mediated via an effect on ERF1 accumulation. Genome‐wide promoter analysis of JA‐induced genes that are suppressed by SA revealed an overrepresentation of the GCC‐box. Using plants that carry the GUS reporter gene under control of four copies of the GCC‐box, we demonstrated that the GCC‐box is a sufficient element for SA‐induced suppression of JA‐induced gene expression. We speculate that SA might repress the JA signaling pathway via interference with binding of JA‐dependent transcription factors to the GCC‐box, such as ERF1 and ORA59.


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8. Characterization and functional analysis of Fusarium oxysporum effectors Fleur Gawehns1, Petra M. Houterman1, Shiv D. Kale2, Ben J.C. Cornelissen1, Martijn Rep1 and Frank L.W. Takken1 1 Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, the Netherlands;2 Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

Fusarium oxysporum f.sp. lycopersici (Fol) is the causal agent of tomato wilt disease. This soil‐born fungus infects roots and invades the xylem vessels eventually resulting in wilting or even plant death. Plant pathogens secrete effectors to manipulate the host and to facilitate infection. When an effector triggers immune responses on a resistant host, it is called an Avr protein. Resistance to Fol is mediated by the I, I‐2 and I‐3 resistance genes that mediate perception of Avr1, Avr2 and Avr3 respectively. Upon host colonization Fol secretes many small proteins (Six proteins) in the xylem sap. Some of these might represent effectors interfering with resistance gene function. Our recent studies showed that three Six proteins, one of them called Six6, suppress the hypersensitive response (HR) of a Nicotiana benthamiana leaf, that coexpresses I2 and Avr2 upon agroinfiltration. Furthermore, we found that Six6 is required for full virulence of Fol. Localization and uptake of Six proteins was studied using different techniques including confocal microscopy and lipid blots. These results and the fact that several Six6 homologues were found in other species of F. oxysporum, indicate an important role of Six6 in the tomato‐Fol interaction. Due to the latter reason we propose a generic target, whose nature is currently investigated.

9. Signal Evolution: Investigating Variations of Symbiotic Calcium Oscillations Emma Granqvist, 1,2, Giles E.D. Oldroyd2, Richard J. Morris1 1Department of Computational & Systems Biology, 2Department of Disease & Stress Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK

Fluctuating calcium concentrations are important in many signalling pathways, such as the establishment of symbioses between plants and microbes. Signal molecules released by both mycorrhizal fungi and nitrogen‐fixing bacteria in the soil activate a common symbiotic signalling pathway in the plant roots. This leads to nuclear and cytosolic calcium oscillations, but downstream events diverge and result in different symbioses. The calcium oscillations are predicted to confer specificity, and we aim to understand how the signals are being distinguished. Furthermore, the bacterial signal pathway is thought to have derived from the more ancient fungal pathway. To test how different calcium signatures could relate to the evolution of the symbiotic signalling pathway, this project investigates calcium oscillations in a phylogenetically wide range of plant species. Calcium concentrations are monitored either by transgenic plants with a calcium reporter gene, or by injecting the plant root hair cells with calcium sensitive dyes. The data presents several challenges in the form of high noise levels and biological variability. Therefore we have developed a novel set of methods to analyse calcium oscillations, including efficient detection of key frequencies with Bayesian Spectrum Analysis and characterisation of phase space dynamics using attractor reconstructions. Mathematical modelling with ODEs describing the underlying machinery allows for further insights into the system's behaviour and for predictions of relevant components. Taken together, this extensive analysis will shed light on the function of symbiotic calcium signals.


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10. Mining natural genetics variation of combinatorial stress responses of Arabidopsis to identify new tolerance pathways for Botrytis cinerea and drough stresses Pingping Huang13; Silvia.Coolen23; Hans van Pelt2; Corné.M.J.Pieterse2 and Mark.G.M Aarts1 1Laboratory of Genetics, Department of Plant Sciences, Wageningen‐UR, The Netherlands; 2Plant‐Microbe Interactions, Department of Biology, Utrecht University, The Netherlands; 3Graduate School Experimental Plant Sciences, Wageningen, The Netherlands

Biotic and abiotic stresses are the most limiting factors that cause heavy crop yield loss. Biotic stress is induced by pathogens and herbivores; pathogens such as Botrytis cinerea (B.cinerea) which is a necrotrophic pathogen fungi can attacks more than 200 crops in agriculture. Abiotic stress includes drought stress is a major stress problem among several abiotic stresses, that can impair plant physiological functions such as inhibit photosynthesis, disturb plant hormone synthesis and distribution, reduce biomass and yield. Plant material uses 360 different and genetically well‐characterized Arabidopsis thaliana (A. thaliana) accessions as plant material to provide an opportunity to explore the natural variation in A. thaliana to B.cinerea and drought combinatorial stress. Genome Wide Association (GWA) mapping is applied in this project as a powerful tool to identify new tolerance pathways. Statistical test programmes such as EMMAX, together with 250K Single Nucleotide Polymorphisms (SNPs) as marker, provide powerful opportunities for identifying new molecular pathway and candidate genes that involved in combinatorial stress responses. Studying the key mechanisms of stress responses in A. thaliana can contribute to improving crop breeding by understanding the similar mechanisms in crops.

11. Pseudomonas syringae Type III Effector, HopU1, targets RNA binding proteins and suppresses the plant innate immune system Anna Joe1,2, Byeong‐ryool Jeong1,3, Ming Guo1,3, Christin Korneli4, Dorothee Staiger4 and Jim Alfano1,3

1Center for Plant Science Innovation,

2School of Biological Science and

3Department of Plant Pathology,

University of Nebraska‐Lincoln, USA; 4Molecular Cell Physiology, University of Bielefeld, Germany

The bacterial pathogen Pseudomonas syringae uses a type III secretion system(T3SS) to inject type III effectors into plant cells and suppress plant immune responds. More than 30 effectors have been identified in P.syringae pv. tomato DC3000 but the enzymatic activities of T3Es and their plant targets remain largely unknown. Among those, DC3000 T3E HopU1 was determined as a mono‐ADP‐ribosyltransferase (ADP‐RT). ADP‐RTs are well known bacterial toxins in animal pathogens where they ADP‐ribosylate and modify specific proteins. Using ADP‐RT assays coupled with mass spectrometry we identified the major HopU1 substrates in Arabidopsis thaliana extracts to be several RNA‐binding proteins that possess RNA‐recognition motifs (RRMs). One of these proteins, GRP7 was shown to be involved in innate immunity. Arabidopsis mutants lacking GRP7 were more susceptible to P. syringae. HopU1 ADP‐ribosylates an arginine residue in position 49 of AtGRP7, which is within its RRM. We found that ADP‐ribosylated AtGRP7 was reduced in its ability to bind RNA. Recently, we also discovered that the plants over‐expressing GRP7 are more resistant to P. syringae further supporting that GRP7 plays an important role in innate immunity.


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12. Ethylene as an early neighbour detection cue Wouter Kegge1, Mieke de Wit1, Laurentius A.C.J. Voesenek1 and Ronald Pierik1

1 Plant Ecophysiology, Department of Biology, Utrecht University, The Netherlands

Plants need to accurately sense their environmental conditions in order to perform optimally. During above ground competition with neighbouring plants, plants respond to changes in both light quantity and quality. Phytochromes are photoreceptors that are sensitive to changes in the red to farred (R:FR) ratio and control shade avoidance responses, including upward leaf movement (hyponasty) and shoot elongation. These shade avoidance responses help plants to optimize light capture in dense vegetations. Standing theory dictates that these responses are induced by reduced R:FR ratio’s already prior to the onset of actual shading in dense vegetations. In a time series with dense canopies of Arabidopsis thaliana, plant responses to neighbours and to changes in light quality were measured. We observed the occurrence of hyponasty early on in canopy development. R:FR ratio’s at this stage of canopy development were found to be too high to induce hyponasty or petiole elongation. This indicates that signals other than R:FR ratio are involved in the very early neighbour responses of this rosette species. Strikingly, ethylene emissions were also enhanced at the time‐points at which hyponasty was first observed. Since ethylene is a volatile compound that can induce hyponasty, the observed increase of ethylene emissions might constitute an early signal for plant neighbour detection that occurs prior to significant changes in R:FR ratio.

13. Exploring basal defence responses to Fusarium culmorum and F. graminearum infection in Arabidopsis floral tissue Helen Kinns1, Jason J. Rudd1, Murray Grant2 and Kim E. Hammond‐Kosack1 1Rothamsted Research, Harpenden, UK, 2Biosciences, University of Exeter, UK

Fusarium Ear Blight (FEB) is a serious disease of small grain cereals, causing massive losses worldwide. This is due to a combination of reduced grain quality and contamination with mycotoxins, which are harmful to both humans and animals. The two main causative agents of FEB in the UK are Fusarium culmorum and F. graminearum. Both F. culmorum and F. graminearum have been demonstrated to infect the floral and silique tissue of Arabidopsis. This provides an effective pathosystem for investigating defence signalling in Arabidopsis against Fusarium spp. through a reverse genetics approach. Three Arabidopsis extreme disease susceptible (eds) mutants, originally identified by Volko et al (1998) based on their enhanced susceptibility to the biotrophic bacterial pathogen Pseudomonas syringae, have already been shown to be more susceptible to floral infection by F. culmorum. Mutants in the NPR1 gene, known for its role in SA signalling, are also more susceptible. Mutants in the JA and ET signalling pathways appear unaffected in their resistance. This indicates that defence in Arabidopsis against Fusarium has more in common with defence against biotrophic pathogens (mediated by SA signalling) than necrotrophs (via JA and ET). The EDS genes required for resistance to both Pseuodmonas and Fusarium have not yet been mapped, and further characterisation of these genes will provide novel insight into plant defence signalling. Analysis of the metabolome of Fusarium infected wild type and eds plants may reveal secondary metabolites required for defence against Fusarium, while positional cloning of the EDS genes will permit the investigation into gene function and patterns of expression, and allow the search for orthologues in wheat which may contribute to breeding efforts for resistance to FEB.


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14. Is recruitment of parasitic wasps beneficial to teosinte, the ancestor of maize? Elvira S. de Lange1, Kevin Farnier1, Rafael Aguilar‐Romero2, Benjamin Gaudillat1, Thomas Degen1, Fernando Bahena‐Juárez3, Ken Oyama2 and Ted C.J. Turlings1 1 Laboratory of Fundamental and Applied Research in Chemical Ecology, Institute of Biology, University of Neuchâtel, Switzerland; 2 Laboratorio de Ecología Genética y Molecular, Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Mexico; 3 Campo Experimental Uruapan, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Mexico

Parasitic wasps can use the odours that plants emit when attacked by insect herbivores to localize these insects and use them as hosts for their offspring. Because the odours supposedly help the plant eliminate herbivorous threats, their emission is often perceived as an indirect defense mechanism. However, parasitic wasps do not immediately kill their hosts, rendering the proposed signalling function of herbivore‐induced plant volatiles quite controversial. We aimed to study the importance of attracting parasitic wasps for plant growth and survival in teosinte, the wild ancestor of maize. In a natural setting in Mexico, the country of origin of maize, we planted three genotypes of teosinte in large field cages. In all cages except the control cage, the plants were infested with second instar larvae of the moth Spodoptera frugiperda, a major pest of maize in the Americas. In some cages, we then released an important co‐occurring natural enemy, either the parasitic wasp Cotesia marginiventris or the wasp Campoletis sonorensis. On the short term, larval parasitism, plant volatile emission and herbivore‐inflicted damage were assessed. On the long term, we recorded plant growth and survival. Preliminary results show that the presence of parasitic wasps dramatically reduced the damage inflicted by the larvae. This may eventually lead to a reduction in plant mortality. Although odour emission data is still being analyzed, these results support the notion that plants benefit from emitting odours and thereby recruiting parasitic wasps. This work contributes to the ongoing debate

on the defensive function of herbivore‐induced volatiles. 15. Genetic mapping of broad resistance to downy mildew in Arabidopsis C24 Dmitry Lapina, Rhonda C. Meyerb, Guido van den Ackervekena a Plant‐Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands; b Heterosis, Department of Molecular Genetics, Leibniz Institute of Plant Genetics and Crop Plant Research, Corrensstrasse 3, 06466 Gatersleben, Germany

The downy mildew oomycete Hyaloperonospora arabidopsidis (Hpa) is an obligate biotrophic pathogen of Arabidopsis. Broad resistance to all tested isolates of this pathogen was identified in Arabidopsis accession C24. Segregation analysis in F2 and backcross (BC) populations from a cross between Col‐0 flc3 and C24 suggests that the resistance is genetically complex. To identify loci underlying resistance against downy mildew we performed QTL mapping using recombinant inbred lines and introgression lines derived from a cross between Col‐0 and C24 [1,2]. The level of susceptibility to Hpa was quantified by scoring the intensity of sporulation and by determining the relative Hpa DNA content in the infected plants. We identified 3 major loci explaining >45% of phenotypic variation with mostly additive effects. Interestingly, C24 carries not only resistance loci but also a susceptibility locus. The F1 progenies of crosses between Col‐0 and introgression lines show intermediate level of susceptibility to Hpa indicating that the major QTLs are co‐dominant. To fine map Arabidopsis QTLs affecting Hpa development we use traditional map based cloning and a BC approach in which resistance loci are eliminated from the C24 genome. The identification of the molecular mechanisms underlying C24 resistance may reveal novel aspects of plant immunity or host genes involved in susceptibility to downy mildew.


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References [1] Torjek O, et al. J Hered. 2008 Jul‐Aug;99(4):396‐406. [2] Torjek O, et al. Theor Appl Genet. 2006 Nov;113(8):1551‐61.

16. Immunity‐related members of the DMR6 family of oxidoreductases in Arabidopsis Nora Ludwig, Joyce Elberse, Tieme Zeilmaker, Guido Van den Ackerveken Plant‐Microbe Interactions, Department of Biology, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands

Arabidopsis mutants lacking a functional DMR6 gene are resistant to infection by the downy mildew Hyaloperonospora arabidopsidis (Hpa). Resistance is associated with enhanced defense gene expression and both resistance and defense was found to require salicylic acid and signaling through the key regulator NPR1 which signals downstream of salicylic acid. The hypothesis that DMR6 is a negative regulator of defense was further supported by the finding that overexpression of DMR6 leads to enhanced susceptibility to a range of pathogens, e.g. Hpa, Phytophthora capsici and the bacterium Pseudomonas syringae pv. tomato. DMR6 is a 2‐oxoglutarate iron (II)‐dependent oxygenase for which no substrate is known yet. Site‐directed mutagenesis confirmed the requirement of conserved catalytic residues for its function as a negative regulator of defense. Structural modeling has allowed the identification of residues important in the predicted substrate binding pocket, the mutation of which strongly reduced the biological activity of the protein. In the Arabidopsis genome more than 200 2‐oxoglutarate iron (II)‐dependent oxygenases are encoded, however, for most no function is known. We have selected a subgroup of DMR6‐related 2‐oxoglutarate iron (II)‐dependent oxygenases which are differentially expressed during pathogen infection and in response to the defense‐related hormones salicylic acid and/or jasmonic acid. Currently we are working on phenotypic analysis of mutants and overexpression lines of these immunity‐related genes, in particular in their altered responses to various pathogens of Arabidopsis. The DMR6‐like oxidoreductases add an additional layer of complexity to the plant immune network.

17. Localization and Function of Effector AVR2 from Fusarium oxysporum Lisong Ma, Petra Houterman, Martijn Rep and Frank Takken Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, PO Box 94215, 1090 GE Amsterdam, the Netherlands

Plant pathogens secret effector proteins to suppress host immunity and promote host colonization. The effector Avr2 of Fusarium oxysporum f.sp. lycopersici (Fol) has been identified by a proteomics approach in xylem sap of infected tomato plants [1]. The Avr2 and I‐2 pair represents the first complete gene‐for‐gene pair of a plant and a xylem‐invading fungal pathogen. It has been shown that Avr2 has a dual role and acts both as an avirulence and virulence factor. Although a hypersensitive response (HR) is not observed following Fol infection of I‐2 tomato plants, PVX‐mediated expression of Avr2 does trigger I‐2‐dependent HR in tomato. An Avr2 knockout of Fol induces less disease symptoms, which indicates that Avr2 is a virulence factor contributing to pathogenicity [2]. Structure‐function analysis of Avr2 reveals that the protein can be divided into a dispensable N‐terminal part (pro‐domain) and a functional C‐terminal domain. GFP‐ or RFP‐tagged Avr2 accumulates in the cytoplasm and nucleus of Nicotiana benthamiana cells upon transient expression using agroinfiltration. Furthermore, RFP‐tagged Avr2 is found inside the cells of tomato roots infected with a


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transgenic Fol strain carrying an Avr2:RFP construct. Together these data indicate that Avr2 can be taken up by the plant and functions inside the host cell. [1] Houterman, P. M., Speijer, D., Dekker, H. L., de Koster, C. G., Cornelissen, B. J. C. and Rep, M. 2007. The mixed xylem sap proteome of Fusarium oxysporum‐infected tomato plants. Mol. Plant Pathol. 8: 215‐221. [2] Houterman, P. M.*, Ma, L.*, van Ooijen, G., de Vroomen, M. J., Cornelissen, B. J., Takken, F. L. W. and Rep, M. 2009. The effector protein Avr2 of the xylem colonizing fungus Fusarium oxysporum activates the tomato resistance protein I‐2 intracellularly. Plant J. 58: 970‐978.

18. A novel high‐throughput forward‐genetic screen to identify key components leading to PAMP‐induced resistance to bacteria

Laura Masini, Cécile Segonzac and Cyril Zipfel The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK

The first layer of plant immunity relies on the recognition of conserved features of microbes termed pathogen‐associated molecular patterns (PAMPs) by surface‐localized pattern‐recognition receptors (PRRs) leading to PAMP‐triggered immunity (PTI). Although the early molecular events of PTI start to be uncovered, the mechanisms that actually lead to plant immunity (ie. restriction of pathogen growth) are still poorly understood. The aim of this project is the identification through forward genetics of molecular components required for plant resistance to bacteria following perception of the bacterial PAMPs flagellin (flg22) by the PRR FLS2. To this goal, a novel high‐throughput assay for bacterial infection on Arabidopsis seedlings is being developed. The screen itself aims at identifying mutants that are impaired in induced resistance to the bacterium Pseudomonas syringae pv. tomato DC3000 (Pto) triggered by flg22.

19. Posttranscriptional regulation of the GRAS protein SCARECROW‐like 14 (SCL14) during plant detoxification processes Alexander Meier, Kerstin Kruse, Corinna Thurow and Christiane Gatz Molekularbiologie und Physiologie der Pflanze, Albrecht‐von‐Haller Institut, Universität Göttingen, Deutschland

Plants are challenged by toxic substances, which are released by man, other plants or attacking pathogens. Additionally, reactive oxygen species can arise in the plant under biotic or abiotic stresses. The detoxification of these substances in the plant can be divided in three steps and are carried out by a set of enzymes, which contains for example cytochrome P450 monooxygenases, glutathione S‐transferases and ABC transporters. At least a part of these detoxification processes are regulated by the Arabidopsis thaliana GRAS protein SCARECROW‐like 14 (SCL14). SCL14 acts together with the bZIP transcription factor TGA2 to activate it’s target genes. SCL14 and TGA2 form a complex, which binds to as‐1 like elements in the promoters of the SCL14 target genes. Since it could be shown that the SCL14/TGA2 complex binds to it’s target promoters in the induced as well in the uninduced state (Fode et al. 2008), the question arises what is the signal for the SCL14 mediated activation of transcription. In the Arabidopsis mutant gsnor1‐3 the SCL14 target genes are hyperinduced in comparison to wildtype. This mutant lacks the enzyme S‐nitroso glutathione reductase, which reduces S‐nitrosylated glutathione, i.e. glutathione whose cysteines are modified by addition of a NO‐group, what leads to a higher amount of S‐nitrosylated glutathione and thus to a higher amount of S‐nitrosylated proteins in the plant. The hyperinduction of the SCL14 target genes might be a hint to the regulation of SCL14 by S‐nitrosylation.


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To investigate the effect of cysteine mutations on the activity of SCL14, a transient assay was established. In this assay, protoplasts or whole leaves from scl14/scl33 double knockout plants are cotransfected with a luciferase gene under the control of truncated versions of the CYP81D11 promoter, a cytochrome P450 monooxygenase and SCL14 target gene, and wildtype SCL14 or SCL14 mutants. These promoter versions can still be activated by SCL14 and gain or loss of induction caused by mutant SCL14 proteins give a hint of the functionality of the mutated aminoacids. The mutant proteins, which show an altered behaviour in comparison to the wildtype protein, are further analyzed to reveal the exact regulation mechanism of SCL14 activity. 20. Transcriptomic response of Lima bean plants to herbivory after low dose phytohormone application T.R. Menzel1, M. Dicke1, J.J.A. van Loon1, R. Gols 1 1Laboratory of Entomology, Wageningen University, The Netherlands

As sessile organisms, plants are under the constant threat of suffering a fatal attack by herbivorous arthropods and all kinds of pathogens. For this reason plants not only possess a remarkable ability to withstand inflicted damage, but have also developed different kinds of defence mechanisms that serve to protect them from their ubiquitous attackers. In general, a distinction is made between direct and indirect protective mechanisms. Direct defences immediately interfere with the attacker and are often delivered as toxins and deterrents, but can also be composed of morphological features such as thorns and trichomes. In contrast, indirect defences exploit the action of higher trophic levels, i.e. predators and/or parasitoids of the attacker, which are summoned by the plants via release of herbivore‐induced plant volatiles (HIPV). Recently, evidence is accumulating that indicates an influence of a primary herbivore attack on subsequent attacks by enhancing or hampering the plant’s defence system. Jasmonic acid (JA) is a key defence hormone, which acts as a signalling molecule after herbivory and controls a set of defence‐related genes in plants that function in direct and indirect defence. We investigated the effect of multiple herbivore attack on the level of indirect defence. A low dose of JA was used to simulate a primary herbivore attack on the Lima bean Phaseolus lunatus. If the plants were also exposed to a secondary attack, using a low density of the herbivorous spider mite Tetranychus urticae, a significant change in the expression level of the gene coding for β‐ocimene‐synthase (OS) occurred that was absent in the water‐treated control plants. The monoterpene β‐ocimene is known to act as a chemical cue for a natural enemy of spider mites, the predatory mite Phytoseiulus persimilis. We suggest that the phytohormone application resulted in an augmentation of indirect defence mediated by β‐ocimene.

21. Specific identification of E3 ubiquitin‐ligase targets Astrid Nagels Durand, Laurens Pauwels and Alain Goossens Department of Plant Systems Biology, VIB and Department of Plant Biotechnology and Genetics, Ghent University, Belgium

The ubiquitin‐proteasome pathway is involved in the regulation of most, if not all, biological processes in eukaryotes. Ubiquitination (Ub) of a target protein is mediated by 3 enzymes (E1, E2 and E3), in which the E3 Ub‐ligase is responsible for recognition of and interaction with the target. Despite the large amount of E3 Ub‐ligases identified in Arabidopsis (>1,400), only a dozen of targets have been identified specifically for a particular E3. By using Tandem Affinity Purification (TAP) of E3 Ub‐ligases, of wildtype and truncated forms, we seek to identify E3‐interactors and thus their


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possible targets. By deleting the region that mediates the E2‐E3 interaction, necessary for the transfer of Ub from the E2 to the target, we expect to achieve enrichment of the target and avoid its’ subsequent degradation. Candidate targets will be subsequently evaluated in a ‘Heterologous Ubiquitination Assay’ (HUBA), which we are currently developing, and in which yeast is used as a host organism. We will use the abovementioned strategies to identify substrates of E3 Ub‐ligases involved in stress responses and hormone signaling in plants.

22. Genetic Analysis Of Seed Longevity In Arabidopsis thaliana Thu‐Phuong Nguyen 1,2 , Paul Keizer 3,4, Fred van Eeuwijk 3,4 and Leónie Bentsink 1,2 1Laboratory of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; 2Molecular Plant Physiology Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands; 3Centre for BioSystems Genomics, 6700ABWageningen, The Netherlands; 4Biometris‐Applied Statistics,Wageningen University and Research Centre, 6708 PB Wageningen, The Netherlands

Seed longevity is one of the most important factors for seed resource conservation and for crop success. It is defined as seed viability after a long time of dry storage (storability) and represents a quantitative trait. During storage seeds age, deteriorate and loose vigour, which ultimately leads to germination failure even under favourable conditions. Six Arabidopsis thaliana recombinant inbred line (RIL) populations, derived from crosses between Landsberg erecta and other accessions, show natural variation for seed longevity after natural storage at room temperature. A mix model quantitative trait loci (QTL) analysis reveals a number of loci for three parameters that could be extracted from the germination curve, the germination rate, the maximum germination and the area under the curve. The two major QTLs have been confirmed by near isogenic lines (NILs) after both natural and artificial ageing (controlled deterioration test). Results indicate that natural variation for seed longevity is regulated by additive genetic pathways.

23. Hexose‐6‐phosphate epimerases: A novel class of apoplastic effectors?

Stan Oome, Guido van den Ackerveken Plant‐Microbe Interactions; Department of Biology, Utrecht University, The Netherlands

The downy mildew Hyaloperonospora arabidopsidis (Ha) is an obligate biotrophic pathogen of Arabidopsis thaliana. It is used as a model system for biotrophic interactions, and the genome sequence of both host and pathogen is available. For infection this pathogen uses two classes of secreted proteins: (i) apoplastic effectors that act outside of the host cell and (ii) hosttranslocated effectors that act inside the plant cell. We have identified a group of apoplastic proteins that are similar to hexose‐6‐phosphate epimerases (H6PEs). These epimerases catalyze the conversion of phosphosugars from the α‐ to the ß‐configuration and back. This is important as some downstream enzymes can only use α or ß sugars; phosphoglucomutase (G6P G1P) and G6P‐isomerase (G6P Fructose‐6P) only use α‐G6P, while G6P‐dehydrogenase (G6P Gluconolactone‐6P) can only use ß‐G6P. Conversion from α‐ to ß‐ and back occurs spontaneously, but the rate is highly increased in the presence of H6PE. The question arises why the oomycetes produce secreted H6PE‐like proteins. Our goal is to understand the role of these proteins in the infection process.


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24. Connecting pathogen perception to transcriptional reprogramming in plant immune responses Nora Peine1, Ana García2, Jaqueline Bautor1 and Jane Parker1 1Department of Plant‐Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, Germany; 2Plant Genomics Research, Unité de Recherche en Génomique Végétale, Institut National de la recherche agronomique, Evry, France In plants, resistance to invading pathogens is mediated by germ‐line encoded receptors residing at the plasma membrane or inside cells. Recognition of pathogen molecules by these receptors triggers an immune response. Robust immunity involving localized plant cell death and massive transcriptional reprogramming is triggered by intracellular Nucleotide Binding‐Leucine‐Rich‐Repeat (NB‐LRR) receptors recognizing specific pathogen effectors. We aim to learn more about processes connecting immune receptor activation to defense outputs. An important component between activation of TIR‐NB‐LRR receptors (which have a Toll‐Interleukin1 Receptor like N‐terminal domain) is the nucleo‐cytoplasmic protein EDS1 (Enhanced Disease Susceptibility1). Together with its interaction and signaling partners, PAD4 and SAG101, EDS1 is required for basal defense to virulent (infectious) biotrophic pathogens and for TIR‐NB‐LRR triggered resistance. In the TIR‐NB‐LRR‐conditioned immune response, EDS1 operates downstream of receptor activation but upstream of cell death initiation, accumulation of ROS (reactive oxygen species), induction of the stress hormone SA (salicylic acid) and transcriptional programming of defense genes. Recent analysis provides evidence that EDS1 shuttles between the cytoplasm and nucleus and that different EDS1 complexes in these compartments cooperate in mediating a complete and balanced immune response. However, how EDS1 and its interacting partners coordinate multiple defense outputs is still not well understood. Transgenic Arabidopsis lines were generated in which EDS1 is forced into the nucleus by fusion to a nuclear localization signal (NLS). Genetic, biochemical and resistance phenotype characterization of transgenic plants expressing EDS1‐NLS under control of the EDS1 promoter or a conditional estradiol‐inducible promoter should allow me to determine how nuclear EDS1 affects expression of particular sets of genes and molecular processes underlying the fine control of multiple plant immune responses.

25. Ethylene‐induced differential petiole growth in Arabidopsis thaliana involves local microtubule reorientation and cell expansion. Joanna K. Polko, Martijn van Zanten, Laurentius A.C.J. Voesenek, Anton J.M. Peeters, Ronald Pierik Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands Hyponastic growth is an upward petiole movement induced by plants in response to various external stimuli. It is caused by unequal (differential) growth rates between adaxial and abaxial sides of the petiole, which brings rosette leaves to a more vertical position. The volatile hormone ethylene is one of the key regulators inducing hyponasty in Arabidopsis thaliana. We studied whether ethylene–mediated hyponasty occurs through local stimulation of cell expansion and if this involves reorientation of cortical microtubules (CMTs). To study cell size differences between ab‐ and adaxial sides of petioles in ethylene and control conditions, we analyzed epidermal imprints. We studied involvement of CMT dynamics in epidermal cells using the tubulin marker line as well as genetic and pharmacological means of CMT manipulation. Our results demonstrate that ethylene induces cell expansion in a restricted abaxial


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region of the proximal side of the petiole and that this can account for the observed differential growth. Ethylene induces CMT reorientation from longitudinal to transverse and inhibition of CMTs disturbed ethylene‐induced hyponastic growth. This work provides evidence that ethylene stimulates local cell expansion within the petiole inducing differential growth, and is associated with dynamic changes in arrangement of CMTs along the petiole.

26. COI1 but not plant‐derived JA is required for Verticillium longisporum propagation and subsequent disease symptoms in Arabidopsis thaliana. Anjali Ralhan, Corinna Thurow, Ivo Feussner, Cornelia Göbel and Christiane Gatz* *Albrecht von Haller Institute for Plant science, Georg‐August‐Universität Untere Karspüle 2, 37073 Göttingen, Germany. *[email protected]

Verticillium longisporum is a soil‐borne fungal pathogen causing vascular disease predominantly in oilseed rape but also in other members of the family Brassicaceae. The fungus enters the root, invades xylem elements, and proliferates in the xylem vessels, where it produces conidia and microsclerotia. As a result of the infection, plants are stunted; show yellow leaf symptoms and decreased yield. Pathogen attack triggers complex signalling cascades regulated by signalling molecules such as salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) resulting in the expression of defence‐related genes. Verticillium‐induced expression of jasmonic acid (JA)‐responsive genes in Arabidopsis thaliana leads us to assess the role of JA defence pathway in this plant‐pathogen interaction. Arabidopsis mutants deficient in JA biosynthesis (dde2‐2; delayed‐dehiscence2‐2) and signalling (coi1‐t; coronatine insensitive 1) were tested for susceptibility. When comparing the leaf area after infection, dde2‐2 and WT plants showed disease phenotype in contrast to coi1‐t plants which remained healthy, indicating the requirement of COI1 but not of JA for development of the disease symptoms. The healthy patho‐phenotype of coi1‐t mutant plants was associated with reduced fungal colonization. Moreover, development of microsclerotia on senescent tissues appeared in a lower percentage on coi1‐t as compared to WT and dde2‐2 mutant plants. To better understand the molecular basis for these differences, whole genome micro array was performed with Verticillium infected WT, dde2‐2 and coi1‐t petioles at 15 dpi. Cluster analysis unravelled a group of genes which shows similar expression in all three genotypes serving as infection markers, genes which are similarly expressed in WT and dde2‐2 in contrast to differential expression in coi1‐t corresponding to the COI1 dependent genes which might be responsible for the patho‐phenotype and genes which are highly expressed only in the WT but not in dde2‐2 and coi1‐t. The latter group represents JA‐ or JA/ET‐ dependent defence marker genes that were up regulated in WT but not in dde2‐2 mutant plants suggesting the absence of fungal derived jasmonate mimics. Therefore, we postulate that Verticillium activates a novel JA‐independent COI1 function required for its successful colonization and consequent disease susceptibility in Arabidopsis thaliana. References [1] Thatcher, L.F., Manners, J.M. and Kazan, K. (2009) Fusarium oxysporum hijacks COI1‐mediated jasmonate signaling to promote disease development in Arabidopsis


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27. Functional analysis of stress‐inducible NAC factors in Arabidopsis thaliana Neena Ratnakaran and Christiane Gatz Albrecht von Haller Institut für Pflanzenwissenschaften, Georg‐August‐Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany

Plants have developed sophisticated strategies to encounter various stresses, biotic and abiotic, via different stress‐tolerance or defense pathways. The ABA pathway is mainly known for regulating responses to abiotic stresses while the SA, JA and ET‐induced pathways act against biotic stresses. The plant's response towards stress invariably leads to positive or antagonistic cross‐talk between different pathways. Indeed the ABA‐ or SA‐ mediated suppression of ET/JA‐responsive genes has been extensively reported. However the mechanisms of such cross‐talk have not yet been fully understood. The family of NAC transcription factors are a group of plant‐specific genes that have been shown to play a role in development and stress responses. There are >100 NAC factors in Arabidopsis and of these the ATAF subfamily has been predicted to play important roles in stress and defense. The members of this subfamily shows a co‐regulated expression by wounding, infection, SA, MeJA, ABA, H2O2, cold, drought, salt and osmotic stresses. The ATAF1 (ANAC002) has been reported to play a negative role in resistance against necrotrophic pathogens by suppression of defense gene PDF1.2 (Wang et.al., 2009). In our lab we could show that another member from this same family, the ANAC032, when over‐expressed, can also suppress MeJA‐induced and ACC‐induced PDF1.2 expression. Moreover, when transient protoplast assays and yeast two hybrid experiments were done, results indicated that ATAF1 has ability to directly bind to EIN3 and suppress promoter activity of ORA59 which acts upstream of PDF1.2. Therefore we speculate that NAC proteins could be an important factor regulating the cross‐talk seen between the ET/JA‐ and other pathways. Loss‐of‐function studies and characterization of other ATAF subfamily members need to be carried out to determine the functions of NAC with respect to stress‐induced responses.

References

1. Wang et. al. 2009. The Arabidopsis ATAF1, a NAC transcription factor, is a negative regulator of defense responses against necrotrophic fungal and bacterial pathogens. MPMI. 22(10):1227‐1238.

28. Molecular and physiological analysis of the drought‐induced flowering response

Riboni M.1, Galbiati M.1, Tonelli C. 1, Conti l.1 1Department of Biomolecular Sciences and Biotecnology, Università degli Studi di Milano, Via Celoria 26, 20133 Milano (Italy)

The floral transition is a key step in plants life. The correct timing of this switch is essential for reproductive success. Therefore, plants have evolved a complex gene network to detect and integrate internal and environmental cues. In Arabidopsis thaliana four main flowering pathways have been defined: the photoperiodic, the autonomous, the vernalization and the gibberellins. These are responsible for the perception of the major internal and environmental signals, e.g. the photoperiodic pathway perceives the day‐length. Little is known about the existence of additional flowering pathways. These allow plants to detect other environmental conditions such as warm temperature (accelerating flowering) or salt stress (delaying flowering). We find that drought also affects flowering time; in fact we notice a significant reduction of vegetative leaves in drought‐treated plants compared to controls. This raises the interesting question of how drought stress is perceived and integrated into the floral transition mechanism. Data will be presented illustrating our experimental approach and the initial characterization of mutants affected in the drought‐induced flowering response. In particular we find that the


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photoperiodic pathway and the ABA hormone seems to play a central role in the drought‐induced flowering response.

29. Control of flowering by environmental stimuli Nicole Rodenburg; Sjef Smeekens; Marcel Proveniers Molecular plant physiology, Utrecht University, 3584 CH Utrecht, The Netherlands

Control over flowering time is important for successful horti‐ and floriculture and the ability to manipulate flowering time is an economically important goal in plant breeding. Timing of flowering is influenced by environmental signals to induce flowering in plants at the most favorable conditions for reproductions to enhance fitness. In Arabidopsis thaliana most studies have focused on, for the plant highly predictable factors involved in flowering, like day length (photoperiod) and extended periods of cold (vernalization). However less predictable factors such as light quality (red:far‐red ratios) and ambient temperature are equally important.

In this project we want to unravel how external factors, with a focus on light quality and ambient temperature, influence flowering of plants. This will provide information, methods and genes that are useful in breeding and production programs to obtain cultivars with a desired time of flowering in response to changing and variable growth conditions. Currently we are studying the physiology of light quality and temperature induced flowering, simultaneously optimizing conditions for genome‐wide expression studies. 30. A proteomics approach to brassinosteroid signalling Glycogen Synthase Kinase3 (GSK3)‐like kinases in Arabidopsis Joanna Schneider‐Pizoń1,2, Ceylan Ayada1,2, Na Li3, Sjef Boeren3, Sacco de Vries3, Geert De Jaeger1,2 and Eugenia Russinova1,2 1Department of Plant Systems Biology, Flanders Institute for Biotechnology, Belgium; 2Department of Plant Biotechnology and Genetics, Ghent University, Belgium; 3Laboratory of Biochemistry, Wageningen University, The Netherlands

Brassinosteroid (BR) signalling is a key hormonal regulatory pathway controlling plant growth and development. Brassinosteroid‐insensitive 2 (BIN2) and six of its homologues, all belonging to the Arabidopsis serine/threonine glycogen synthase kinase3 (GSK3)/SHAGGY‐like kinases have been linked to BR signal transduction based on their ability to phosphorylate BR responsive transcription factors and to negatively regulate the BR responses. In order to unravel novel regulatory proteins of the BR‐related GSK3‐like kinases, Tandem Affinity Purification (TAP) and single affinity purification have been applied to Arabidopsis cell cultures and plants expressing tagged versions of the kinases. Only single affinity purifications using TAP or GFP tags allowed the identification of putative kinase interactors. The results obtained from multiple purifications were compared and candidate proteins have been selected for further validation. Co‐immunoprecipitation experiments and bimolecular fluorescent complementation analysis have so far confirmed the interaction between BIN2 and four novel proteins. The present study identifies novel components of BR signalling pathway and contributes to the understanding of its regulation.


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31. Cracking the code of bZIP dimerization in Arabidopsis

Jebasingh Selvanayagam 1, Monika Tomar1,Evelien van Eck‐ Stouten1, Micha Hanssen1, Andrea Ehlert4, Wolfgang Droge‐Laser 4, Sjef Smeekens1,2 and Johannes Hanson1,2,3 1Molecular Plant Physiology, Faculty of Science, Padulaan 8,3584 CH Utrecht, The Netherlands;

2Centre for

Biosystems Genomics PO 98, 6700AB Wageningen, The Netherlands; 3Umea Plant science Centre, Department

of Plant Physiology, Umea university, SE – 901 87, Umea, Sweden; 4Julius –Maximillians – Universität Würzburg,

Julius –von‐Sachs‐institut for Biowissenschaften, Lehrstuhl fur Pharmazeutische biologie, Molekularbiologie und Biotechnologie der Pflanze, Julius‐von‐Sachs Platz 2, 97082, Würzburg, Germany.

S1 group Basic Leucine Zipper Protein (bZIP) transcription factors (bZIP1, bZIP2, bZIP11, bZIP44, bZIP53) form heterodimers with C group (bZIP9, bZIP10, bZIP25, bZIP53) bZIP transcription factors. The dimers bind to ACGT core motives which have been identified in a multitude of plant genes regulated by diverse environmental, physiological, and environmental cues. Specific S1/C dimer formation has been demonstrated using both Yeast two hybrid and Plant two hybrid analysis. Our Microarray analysis show that different dimers regulate different genes in a specific manner. Interestingly, bZIP11 is affecting gene expression significantly more than other tested bZIP proteins both even expressed alone or in combination with dimerizing partners. However, dimerization is in all cases enhancing activity of all bZIPs including bZIP11. Moreover, using gain and loss of function reveals the importance of bZIPs dimer regulation in plants. Based on this, our proposed model suggests that the combinatorial control of amino acid metabolism and regulation of stress target genes are controlled by specific heterodimers of bZIP transcription factors.

32. The TOC Complex May Mediate the Plastid Localization of a Gravity Signal Transducer in Arabidopsis

Allison Strohm1,2 and Patrick Masson1 1Laboratory of Genetics, University of Wisconsin‐Madison, USA; 2Graduate Program in Cellular and Molecular Biology

Plant roots navigate their heterogeneous soil environments partly through their abilities to sense and respond to gravity. This process involves the sedimentation of dense amyloplasts in the columella cells of the root tip onto the cortical ER or plasma membrane. A genetic screen identified a preprotein receptor (TOC132) of the Translocon at the Outer envelope membrane of Chloroplasts (TOC) complex, as a contributor to gravity signal transduction. The TOC complex transports nuclear‐encoded proteins from the cytosol into plastids and plastid membranes. To determine if TOC132 functions directly as a gravity signal transducer or indirectly by mediating the plastid localization of such a transducer, additional TOC complex components were tested for involvement in gravitropism. Similarly to mutations in TOC132, mutations in genes encoding the preprotein receptors TOC120 (which functions redundantly with TOC132 in the import of non‐photosynthetically‐related proteins into plastids) and TOC34 also enhance the gravitropic defects associated with mutations in ALTERED RESPONSE TO GRAVITY 1. Furthermore, the cytoplasmic acidic domain of TOC132 is not required for a gravitropic response. These data suggest that the TOC complex may function in gravitropism indirectly by mediating the localization of a plastid‐associated molecule that transduces the signal. I have conducted double mutant analyses to place the TOC complex in a genetic model for gravity signal transduction, and my current work centers on a mutagenesis approach to identify new signal transducers potentially associated with the amyloplast. This work suggests an important role for amyloplasts in gravity signal transduction beyond their simple ability to sediment.


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33. Study of the interaction between Rhizoctonia solani and Arabidopsis thaliana via a transcriptomic approach. Pieter Timmermans1, Janick Mathys1, Mieke Vanhaecke1, Bruno P.A. Cammue1 and Barbara De Coninck1 1Centre of Microbial and Plant Genetics, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20 , 3001

Leuven, Belgium

Rhizoctonia solani is a soil born, necrotophic pathogen causing diseases in many economically important crops all over the world. Up to now R. solani research is mostly focused on characterization of isolates and controlling the disease via biocontrol organisms but to a lesser extent on studying the molecular interaction between R. solani and plants. In this study we use the model plant Arabidopsis thaliana to elucidate the induced plant defense response upon R. solani (AG2.2.IIIB) infection. Using microarray analysis of leaf tissue we identified approximately 700 genes that were differentially expressed (DE) at 48h post R. solani inoculation. At first the DE genes were classified according to their biological pathways resulting in a holistic picture of the defense signaling cascades. Defense signaling mutants were used to confirm the role of the salicylic acid, ethylene and jasmonic acid signaling pathway in the susceptibility of A. thaliana towards R. solani. Secondly we focused on several highly upregulated genes and are currently investigating the role of those genes in the defense response working with overexpression and silencing lines or using known T‐DNA insertion mutants. By elucidating the basis of the plant defense reaction we aim at generating valuable knowledge that can be used in the development of more R. solani resistant field crops.

34. Homologs of the Pseudomonas syringae HopA1 effector are differentially recognized in plants and resembles phosphothreonine lyases from animal pathogens Tania Toruño1, Alexander Singer2, Ming Guo1, Alexei Savchenko2 and James Alfano1 1 Center for Plant Science Innovation and Department of Plant Pathology, University of Nebraska‐Lincoln, Nebraska, USA; 2 C.H. Best Institute, University of Toronto, Toronto, Ontario, Canada

Pseudomonas syringae is a host specific plant bacterial pathogen that requires a type III protein secretion system to inject effector proteins into plant cells for pathogenicity. The effector protein HopA1 was first characterized in P. syringae pv. syringae 61 and is encoded by a gene located in the Hrp pathogenicity island. Another strain, P. syringae pv. tomato DC3000, contains a hopA1 allele in a different region of the chromosome. HopA1Psy61 and HopA1PtoDC3000 are 57% identical but have different host specificity. In tobacco and Arabidopsis accession Ws‐0, HopA1Psy61 but not HopA1PtoDC3000 elicits a hypersensitive response (HR), consistent with HopA1Psy61 being recognized by a plant immune receptor. Expression of HopA1 in yeast, a model eukaryotic system, revealed that only HopA1Psy61 inhibits yeast growth. HopA1 shares sequence similarity with the Photorhabdus luminescens insecticidal toxin Mcf2. The HopA1PtoDC3000 C‐terminal region was crystallized and shows similarity with structures of the phosphothreonine lyases OspF from Shigella and SpvC from Salmonella. Five conserved residues between HopA1 alleles and Mcf2 toxins, which also correspond to the functionally important residues in the phosphothreonine lyase active site, were mutated to alanine. We determined the effects that these substitutions have on the ability of HopA1Psy61 to elicit an HR and inhibit yeast growth.


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35. Natural Variation of submergence tolerance among Arabidopsis thaliana accessions Vashisht D1,2, Hesselink A1, Pierik R1, Ammerlaan JMH1, Bailey‐Serres J3, Visser EJW4, Pedersen O5, van Zanten M1,6, Vreugdenhil D2,7, Jamar DCL2,7, Voesenek LACJ1,2, Sasidharan R1,2

1Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands; 2Centre for Biosystems Genomics, 6708 PB Wageningen, The Netherlands; 3Center for Plant Cell Biology,University of California, Riverside, CA 92521; 4Radboud University Nijmegen, Institute for Water and Wetland Research, Department of Experimental Plant Ecology, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands; 5The Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, 3400 Hillerød, Denmark; 6Department of Plant Breeding and Genetics, Max Planck Institute for Plant Breeding Research, Carl‐von‐Linné‐Weg 10, 50829 Cologne, Germany;7Lab of Plant Physiology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands. Contact ID: [email protected]

Flooding is a natural phenomenon which has severe impacts on the productivity of arable farmland, as most crops are flood‐intolerant. Despite some knowledge on the adaptive responses of tolerant plants under low oxygen conditions, surprisingly little is known about (i) the relation between gene regulation and plant survival upon flooding and (ii) the genes and processes that determine variation in flooding tolerance. We therefore selected 86 accessions of Arabidopsis from different geographical locations around the world to identify and characterize key regulatory components required for flooding tolerance. Seedlings (10 leaves) from these accessions were completely submerged under dark conditions at 20 °C and then de‐submerged at different time points after which they were allowed to recover from the flooding stress. Tolerance was expressed as the number of submergence days till 50% of population dies (LT50). 86 accessions showed strong variation for flooding tolerance ranging from extreme (accession C24 with an LT50 of 11.2 days) to low tolerance (accession Cvi‐0 with an LT50 of 4.01 days). We also measured the initial carbohydrate content in the shoot tissue and the relative petiole growth. This was correlated to the tolerance level of the 86 accessions. Three tolerant, 3 intolerant and 3 intermediate accessions were submerged under dark and light conditions to check the robustness of the tolerance ranking. We also measured the oxygen concentrations in petioles and roots during flooding in tolerant and intolerant accessions. In future, transcript profiling will be done to identify and characterise genes involved in flooding stress.

36. Regulation of contrasting flooding responses: a RNA‐seq approach in two Rumex species Hans van Veen1, Angelika Mustroph2, Julia Bailey‐Serres3, Laurentius A.C.J. Voesenek1, Rashmi Sasidharan1 1. Plant Ecophysiology, Institute of Environmental Biology, Utrecht University, Padualaan 8, 3584 CH, Utrecht, the Netherlands; 2. Department of Plant Physiology, University of Bayreuth, Universitaetsstrasse 30, 95440 Bayreuth, Germany; 3. Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA

Flooding is a major recurring event in many ecosystems and agricultural areas and has adverse effects on normal plant function. The reduced survival is mainly due to reduced gas diffusion underwater, which is 10.000 times slower than in air. In the plant kingdom, two strategies have been identified for dealing with submergence stress. One is a quiescent strategy, where, by suppressing growth and energy demanding processes, valuable carbohydrates are saved. The other is an escape strategy where either petioles or internodes show a vigorous upward elongation to make contact with the water surface. The subsequently established


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air contact allows for enhanced gas exchange with the still submerged plant organs via aerenchyma (air conducting tissue). Knowledge on the regulatory mechanisms underlying these adaptive strategies is therefore crucial for understanding how plants deal with flooding stress. To further elucidate these processes we used a RNAseq approach on two related wild species Rumex acetosa (quiescent) and Rumex palustris (escape). Using the 454 platform (roche) long readlengths (450 bp) were obtained which facilitated de novo assembly of a transcriptome library for both species. Subsequently, global gene expression upon flooding was determined by mapping a high number (30*106) of shorter reads (100 bp) obtained by solexa sequencing back to the transcriptome libraries. Results from this study revealed a differential regulation of several established and novel regulatory components involved in the regulation of submergence‐induced growth responses. These include genes involved in hormone metabolic and regulatory pathways (e.g. ethylene and ABA signaling), growth machinery (cell‐wall modifying proteins) and regulation of oxidative stress (hemoglobin, glutathione biosynthesis).

37. The arbuscular mycorrhizal fungus Glomus intraradices reduces growth and infects roots of the non‐host plant Arabidopsis thaliana Rita S. L. da Veiga1, 2, Antonella Faccio3, Andrea Genre3, Corné M. J. Pieterse2, Paola Bonfante3 and Marcel G. A. van der Heijden1, 2 1 Ecological Farming Systems, Agroscope Reckenhoz‐Tänikon ART Research Station, Switzerland; 2 Plant‐Microbe Interactions, Department of Biology, Utrecht University, The Netherlands; 3 Department of Plant Biology, Istituto Protezione Piante – Consiglio Nazionale delle Ricerche, University of Turin, Italy

Non‐mycorrhizal plants are present in most terrestrial ecosystems but little is known about their interactions with arbuscular mycorrhizal fungi (AMF). This study investigates effects of the AM fungus Glomus intraradices on growth and root infection of the non‐mycorrhizal plant Arabidopsis thaliana. To assess growth responses, two glasshouse experiments were conducted using a dual compartment system in which A. thaliana was grown alone or together with the mycorrhizal hosts Trifolium pratense or Lolium multiflorum, in the presence or absence of G. intraradices. The host plants in the system ensured the presence of an active mycorrhizal network. The AM fungal networks caused growth (measured as aboveground biomass) depressions in A. thaliana of more than 50% compared to non‐inoculated controls. When A. thaliana was grown in the presence of G. intraradices but in the absence of the host plant, no growth reduction was observed. Light, confocal and electronic microscopy revealed that G. intraradices supported by its host plant was capable of colonizing A. thaliana tissues but these seemed to be senescing or dying. The results obtained here reveal an unexpected susceptibility of A. thaliana to G. intraradices, proposing A. thaliana as a suitable model plant to study non‐host/AMF interactions and the biological basis of AM incompatibility.


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38. Fructose sensitivity is suppressed in Arabidopsis by the transcription factor ANAC089 lacking the membrane‐bound domain. Julia Wind1, Sjef Smeekens1, Sheng Teng1,2, Johannes Hanson1 1Molecular Plant Physiology, Faculty of Science, Padulaan 8,3584 CH Utrecht, The Netherlands; 2Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, The Chinese Academy of Sciences, Shanghai 200032, China

Sugar repression of seedling development was used to study fructose sensitivity in the Landsberg erecta (Ler)/Cape Verde Islands (Cvi) recombinant inbred line population, and FSQ6 was confirmed to be a fructose‐specific QTL by analyzing near‐isogenic lines in which Cvi genomic fragments were introgressed in the Ler background. These results indicate the existence of a fructose‐specific signaling pathway in Arabidopsis. Remarkably, fructose specific FSQ6 downstream signaling interacts with abscisic acid (ABA)‐ and ethylene‐signaling pathways, similar to HXK1‐dependent glucose signaling. The Cvi allele of FSQ6 acts as a suppressor of fructose signaling. The FSQ6 gene was identified using map based cloning approach, and FSQ6 was shown to encode the transcription factor gene Arabidopsis NAC domain containing protein 89 (ANAC089). Controlled proteolytic activation of membrane‐bound transcription factors (MTFs) is a versatile way of rapid transcriptional responses to environmental changes in plants. Amongst NAC (NAM/ATAF1/2/CUC2) transcription factors, at least 45 are considered MTFs, of which ANAC089 is one. The Cvi allele of FSQ6/ANAC089 is a gain‐of‐function allele caused by a premature stop in the third exon of the gene. The truncated Cvi FSQ6/ ANAC089 protein lacks a membrane association domain that is present in ANAC089 proteins from other Arabidopsis accessions. As a result, Cvi FSQ6/ANAC089 is constitutively active in the nucleus.

39. Competition for light severely hampers defence signalling in Arabidopsis thaliana Mieke de Wit, Laurentius A.C.J. Voesenek, Ronald Pierik Institute of Environmental Biology, Utrecht University, Padualaan8, 3584 CH Utrecht, [email protected]

Crops are typically grown in high densities where competition for light with weeds is intense and diseases can spread rapidly. It is, however, unknown how plants can deal with both these major stress factors simultaneously. Therefore, we investigate whether there is an interaction between the shade avoidance response to light competition and the defence response to pathogen attack, and take a genomics approach to study how plant signalling is affected when both stress responses are induced. We show here that plants responding to a low red:far‐red light ratio (low R:FR; the predominant neighbour detection signal) are more susceptible to pathogens than plants in control light. Notably, infected plants still exhibited low R:FR‐induced petiole elongation, indicating that shade avoidance was prioritized over disease resistance. Indeed, induction of immune‐related genes by the defence hormones salicylic acid (SA) and jasmonic acid (JA) was markedly reduced in low R:FR‐treated plants, while shade avoidance and the associated marker gene expression were unaffected by the defence response. To elucidate the mechanisms underlying the suppression of defence during shade avoidance, microarray studies were performed on plants simultaneously treated with low R:FR and SA or JA. Low R:FR treatment resulted in massive downregulation of both defence responses; 84% and 44% of all differentially expressed genes in SA‐ and JA‐treated plants, respectively, were suppressed in the combined treatment. Strikingly, the transcript profiles of the two defence pathways do not overlap in the combined treatment with low R:FR, suggesting that low R:FR inhibits both defence routes through independent mechanisms.


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40. The role of root‐specific MYB72 transcription factor during rhizobacteria‐induced systemic resistance in Arabidopsis Christos Zamioudis, Rogier Doornbos, Sjoerd van der Ent, Peter Bakker and Corné Pieterse Plant‐Microbe Interactions, Institute of Environmental Biology, Utrecht University, P.O. Box 800.56, 3508 TB Utrecht, The Netherlands

Root colonization by selected strains of non‐pathogenic rhizobacteria triggers an induced systemic resistance (ISR) in diverse plant species that is effective against a broad spectrum of pathogens and even insects. In Arabidopsis, a transcriptomics‐based approach identified the root‐specific transcription factor MYB72 as an important component for the establishment of ISR. MYB72 is locally induced upon root colonization by Pseudomonas fluorescens WCS417r and T‐DNA mutants disrupted in MYB72 abolished in their ability to generate ISR against a broad range of pathogens. A survey in the Arabidopsis transcriptome using Genevestigator data revealed that MYB72 expression is specifically induced under iron limited conditions. Here, we report that rhizobacteria capable of triggering ISR in Arabidopsis, are also able to upregulate iron deficiency mechanisms locally in the roots. We further demonstrate that WCS417r‐induced expression of MYB72 is depended on FIT1, the central regulator of iron acquisition in the roots. Constitutive high‐level expression of FIT1 is not sufficient to induce MYB72 expression. However, overexpression of FIT1 together with either the bHLH38 or bHLH39 transcription factor converted the expression of MYB72 to constitutive, indicating that the transcriptional regulation of MYB72 during ISR is similar to that of the iron uptake genes FRO2 and IRT1. MYB72 is predominantly expressed in the vascular bundle; however, upon colonization by WCS417r, it is expressed in the epidermal and cortical cells. Microarray analysis further identified a number of WCS417r‐induced genes that are regulated in a MYB72‐dependent manner. These include the beta‐glucosidase BGLU42, the cytochrome P450 monooxygenase CYP71B5, the oligopeptide transporter NTR1.8 and a gene of unknown function. Remarkably, a cluster of defense‐related genes showed increased expression in the myb72 mutant and compromised expression in the MYB72 overexpression line, indicating that WCS417r may trigger MYB72 expression in order to attenuate local immune responses and establish successful infections. Accordingly, active root colonization by WCS417r was found to be impaired in the myb72 mutant.

41. Identification of SC‐peptide associated proteins Jeroen Lastdrager, Maureen Hummel, Sjef Smeekens and Johannes Hanson Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, P.O. Box 800.56, 3508 TB Utrecht, The Netherlands

Changed cellular sugar levels are dramatically affecting gene expression in plants. The bZIP11 transcription factor plays a part in this regulatory pathway by affecting genes encoding key enzymes in primary metabolism, thereby acting as a dominant regulator of metabolism (1). In response to high sucrose levels, bZIP11 is translationally repressed, which depends on the sucrose control (SC) peptide encoded by an upstream open reading frame (uORF) in the 5’‐leader of bZIP11 mRNA (2). A likely model includes stalling of ribosomes on the bZIP11 mRNA due to sucrose‐dependent interactions of the translated SC‐peptide with ribosomal or ribosome associated factors (3). This regulatory principle is well conserved and unique to plants. Transgenic Arabidopsis lines expressing an immuno‐tagged SC peptide are being developed, allowing the enrichment and identification of interacting proteins. Additionally, a Yeast‐2‐Hybrid screening approach yielded several possible protein interactors of the SC‐peptide. These experiments could lead to the identification of proteins or protein modifications involved in sucrose dependent stalling of translation and sugar signaling mechanisms in plants.


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42. The Arabidopsis transcription factor bZIP11 reprograms sugar metabolism Jingkun Ma, Micha Hanssen, Krister Lundgren, Lázaro Hernández, Thierry Delatte, Andrea Ehlert, Chun‐Ming Liu, Henriette Schluepmann, Wolfgang Dröge‐Laser, Thomas Moritz, Sjef Smeekens and Johannes Hanson Molecular Plant Physiology, Institute of Environmental Biology, Utrecht University, P.O. Box 800.56, 3508 TB Utrecht, The Netherlands

The Arabidopsis transcription factor bZIP11 is regulated by sucrose. It is known to act downstream of SnRK1 kinase, regulating amino acid metabolism. Furthermore, it is suggested that bZIP11 has a broader regulatory effect in metabolism. By employing large‐scale metabolomic and transcriptomic approaches, we analyzed the regulatory effects of bZIP11 using bZIP11 dexamethasone nuclear translocation inducible lines. Induced bZIP11 activity reprograms sugar metabolism rapidly. Moreover, bZIP11 regulates trehalose metabolism probably via transcriptional activation on several corresponding metabolic genes, TRE1, TPP5 and TPP6. Over‐expression of bZIP11 rescues the growth inhibition caused by exogenously applied trehalose. Importantly, bZIP11 induction lowered the contents of trehalose 6‐phosphate, which has been proposed as signaling molecule. These findings indicate a possible interaction between two cellular sugar sensing systems which involve trehalose 6‐phosphate and SnRK1 respectively.

EPS Summerschool Participants

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List of participants

Name Institute Country Email

Ahamad, S. Rothamsted Research UK [email protected]

Anong, A. MEAO Cameroon [email protected]

Beyers, T. KU Leuven Belgium [email protected]

Cheng, X. Wageningen UR Netherlands [email protected]

Coolen, Silvia Utrecht University Netherlands [email protected]

Cuéllar Pérez, Maria Ghent University Belgium [email protected]

Czerednik, Anna Utrecht University Netherlands [email protected]

Danquah, Agyemang INRA Evry France [email protected]

Dávila Olivas, Nelson Wageningen UR Netherlands [email protected]

De Cremer, Kaat KU Leuven Belgium [email protected]

De Lange, Elvira University of Neuchâtel Switzerland [email protected]

De Wit, Mieke Utrecht University Netherlands [email protected]

Deroover, Sofie KU Leuven Belgium [email protected]

Diaz, Tabata Universidad de Malaga Spain [email protected]

Gankema, Paulien Utrecht University Netherlands [email protected] Gawehns-Bruning, Fleur

University of Amsterdam Netherlands [email protected]

Granqvist, Emma John Innes Centre UK [email protected]

He, Hanzi Wageningen UR Netherlands [email protected]

Ho, Viet The University of Pisa Italy [email protected]

Huang, Pingping Wageningen UR Netherlands [email protected]

Iglesias, Juliana University of Strasbourg France [email protected]

Joe, Anna University of Nebraska-Lincoln USA [email protected]

Joosten, Jacqueline Genetwister Netherlands [email protected]

Julkowska, Magdalena University of Amsterdam Netherlands [email protected]

Kalhorzadeh, Pooneh University of Ghent Belgium [email protected]

Kegge, Wouter. Utrecht University Netherlands [email protected]

Khaling, Eliezer University of East Finland Finland [email protected]

Kinns, Helen Rothamsted Research UK [email protected]

Kissoudis, Christos Wageningen UR Netherlands [email protected]

Kloth, Karen Wageningen UR Netherlands [email protected]

Lapin, Dmitry Utrecht University Netherlands [email protected]

Lastdrager, Jeroen Utrecht University Netherlands [email protected]

Li, Tao University of East Finland Finland [email protected]

Ludwig, Nora Utrecht University Netherlands [email protected]

Ma, Jingkun Utrecht University Netherlands [email protected]

Ma, Lisong University of Amsterdam Netherlands [email protected]

Madsen, Svend University of Copenhagen Denmark [email protected]

Masini, Laura The Sainsbury Laboratory UK [email protected]

Meier, Alexander University of Goettingen Germany [email protected]

Menzel, Tila Wageningen UR Netherlands [email protected]

Mikheili, Misha Ilia State University Georgia [email protected]

Millenaar, Frank Monsanto Netherlands [email protected]

Nagels durand, Astrid University of Ghent Belgium [email protected]

Nguyen, Duy Radboud University Netherlands [email protected]

Nguyen, Thu-Phuong Utrecht University Netherlands [email protected]

Oluowo, Elohor University of Benin Nigeria [email protected]

Oome, S. Utrecht University Netherlands [email protected] Palanisamy, Senthilkumar

Bharathiar University India [email protected]

Paschalidou, Foteini Wageningen UR Netherlands [email protected]


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Peine, Nora MPI Köln Germany [email protected]

Pizon, Joanna VIB Ghent Belgium [email protected]

Polko, Joanna Utrecht University Netherlands [email protected]

Ralhan, Anjali Universität Göttingen Germany [email protected]

Ratnakaran, Neena Universität Göttingen Germany [email protected]

Riboni, Matteo Università degli Studi di Milano Italy [email protected]

Rodenburg, Nicole Utrecht University Netherlands [email protected]

Schimmel, Bart University of Amsterdam Netherlands [email protected]

Schnaubelt, Daniel University of Leeds UK [email protected] Selvanayagam, Jebasingh.

Utrecht University Netherlands [email protected]

Stassen, Joost Utrecht University Netherlands [email protected]

Strohm, Allison University of Wisconsin - Madison USA [email protected]

Thoen, Manus Wageningen UR Netherlands [email protected]

Timmermans, Pieter KU Leuven Belgium [email protected]

Tomar, Monika Utrecht University Netherlands [email protected]

Toruño, Tania University of Nebraska-Lincoln USA [email protected] Van der Does, Dieuwertje.

Utrecht University Netherlands [email protected]

Van der Ent, Sjoerd. Monsanto Netherlands [email protected]

Van Veen, Hans Utrecht University Netherlands [email protected]

Van Zanten, Martijn Utrecht University Netherlands [email protected]

Vashisht, Divya Utrecht University Netherlands [email protected]

Veiga, Rita Agroscope Switzerland [email protected]

Villarroel, Carlos University of Amsterdam Netherlands [email protected]

Vos, Irene Utrecht University Netherlands [email protected]

Wille, Wibke University of Copenhagen Denmark [email protected]

Wind, Julia Utrecht University Netherlands [email protected]

Xiao, Tingting Wageningen UR Netherlands [email protected]

Yasmin, Sabina Scuola superiore sant'anna, Pisa Italy [email protected]

Zamioudis, Christos Utrecht University Netherlands [email protected]

Zhang, Yanxia Wageningen UR Netherlands [email protected]

Zhu, Feng Wageningen UR Netherlands [email protected]


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Invited Speakers and Organizers

Name Institute Country Email

Alfano, James University of Nebraska-Lincoln USA [email protected] van den Ackerveken, Guido

Utrecht University The Netherlands [email protected]

Baena Gonzalez, Elena

Instituto Gulbenkian de Ciência, Oeiras Portugal [email protected]

Bailey Serres, Julia University of California, Riverside USA [email protected]

Ballaré, Carlos University of Buenos Aires Argentina [email protected]

Blilou, Ikram Utrecht University The Netherlands [email protected]

Cutler, Sean University of California, Riverside USA [email protected]

Dirks, Rob RijkZwaan The Netherlands [email protected]

Goossens, Alain VIB Plant Systems Biology Belgium [email protected] van der Heijden, Marcel

Agroscope Switzerland [email protected]

Katagiri, Fumi University of Minnesota - St. Paul USA [email protected]

Keurentjes, Joost Wageningen UR The Netherlands [email protected]

Peeters, Ton Utrecht University The Netherlands [email protected]

Pieterse, Corné Utrecht University The Netherlands [email protected]

Prat, Salomé Centro Nacional de Biotecnología, Madrid Spain [email protected]

Proveniers, Marcel Utrecht University The Netherlands [email protected]

Rutjens, Bas John Innes Centre, Norwich/Utrecht University UK/NL [email protected]

Smeekens, Sjef Utrecht University The Netherlands [email protected]

Spoel, Steven University of Edinburgh UK [email protected]

Ton, Jurriaan Rothamsted Research UK [email protected]

Wigge, Philip John Innes Centre, Norwich UK [email protected]


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