Adams (WHRI University of Warwick), Andrea Massiah (WHRIUniversity of Warwick)

Plants undergo a series of qualitative transitions during their life-cycle in response to both environmental and internal factors. One of themost distinguishable is the transition from a vegetative to reproductivephase of development. This stage is preceded by the juvenile to adulttransition within the vegetative phase. During the juvenile phase (JP)plants are incompetent to initiate reproductive development and areeffectively insensitive to photoperiod. With the change to adult phase,plants attain competence to respond to floral inducers,which is requiredfor the transition to the reproductive phase.

Here we exploit Antirrhinum, a facultative long day plant that has adefined JP that is sensitive to light, to understand the genetic andenvironmental factors that regulate juvenility. A physiological assay hasbeen developed in Antirrhinum that exploits photoperiod sensitivity toallow the length of the JP to be estimated. Environmental factors such asirradiance and CO2 concentrations have been found as key modifiers ofthe length of the JP. A correlation between limiting photosyntheticassimilates and vegetative phase transition has been revealed by HPLCanalysis of total soluble carbohydrates in plants at defined develop-mental stages. Studies are being carried out to determinewhether plantsare florally incompetent during the JP due to inactivity of thephotoperiodic floral induction pathway.

Email Address for correspondence: I.Matsoukas@warwick.ac.uk

doi:10.1016/j.cbpa.2009.04.442

P2.816:35 Monday 29th June 2009Flowering time diversity inMiscanthus: A tool for the optimisationof biomass

Elaine F. Jensen (IBERS)

The C4 tropical grass, Miscanthus, is a leading candidate for theprovision of carbon neutral energy. Increasing pressures on land forfood and fuel necessitate the optimisation of all crops for yield andquality. IBERS hosts one of the largest collections of Miscanthusgermplasm and is the site of diverse and coordinated studies aimed atidentifying and breeding top-performing Miscanthus varieties.

Plants grown for biomass require the longest possible season ofvegetative growth as the switch to reproductive growth slows or stopsbiomass accumulation. Floral transition can also mark the initiation ofsenescence,whennutrients are remobilised to theunderground rhizomefor over-wintering. This remobilisation is critical for carbon neutrality, aswell as improving combustion efficiency through the removal of harmfulelements.

Phenological data accumulated over three years suggest awide rangeof photoperiodic and thermal time requirements for floweringwithin theIBERS germplasm collection. This collection is the basis from whichadditional resources have been developed and are being used forassociation studies. A candidate gene approach has been adopted usingsequences known to regulate floral transition in model species such asArabidopsis andrice. Ageneticmap isunderconstruction andquantitativetrait loci will be identified using this and an F1mapping family exhibitingdiverse flowering times. In addition, transverse sections of plants grownin a controlled environment provide preliminary data concerning thephotoperiodic and thermal time requirements of a number of genotypes,as well as days to heading following floral initiation.

Email Address for correspondence: fft@aber.ac.uk

doi:10.1016/j.cbpa.2009.04.443

P2.9Poster Session — Monday 29th June 2009The EMS1 receptor kinase is required for non-meristematicproliferation of the Arabidopsis anther tapetum

Xiaoqi Feng (University of Oxford)

Animal cell fate is established following a fixed number and patternof divisions of founder cells, whereas in plants cells are generated bymeristems and acquire fates relying on positional signals. An exceptionmay be in reproductive organs where, strict control appears to beexerted over the patterning and number of divisions of the parietallayers of the microsporangia.

We describe a signalling pathway required specifically for thepatterned division of, and fate establishment in a small population oftapetal founder cells located at the periphery of the microsporogen-ous cells. Arabidopsis plants defective of the LRR receptor kinaseEMS1/EXS, a member of this pathway, fail to form a tapetal cell layer.Instead, cells formed from the archesporial lineage that normally giverise to the tapetum remain undifferentiated, and the meiocytes areover-proliferated. Using the AtA9 tapetal-specific promoter (normallyactivated once the tapetum is formed) to drive the EMS1 kinase inems1 plants, we have succeeded in reactivating these tapetal‘founder’ cells inducing both division pattern and tapetal fate, andsuppression of meiocyte over-proliferation.

Our data show conclusively the tapetal cell layer of the Arabidopsismicrosporangium to be formed as a result of patterned anticlinaldivisions by a small group of founder cells located at the periphery ofthe sporogenous cells, confirming that tapetal and sporogenous cellsare derived from distinct cell lineages. We also demonstrate that asignalling pathway including both the EMS1 receptor kinase and itsputative ligand TPD1, is necessary for this pattern of division.

Email Address for correspondence: xiaoqi.feng@plants.ox.ac.uk

doi:10.1016/j.cbpa.2009.04.444

P2.10Poster Session — Monday 29th June 2009How to change your fate

Katja E. Jaeger (John Innes Centre), Sergey Lamsin (University ofTuebingen), Philip A. Wigge (John Innes Centre), Richard Morris(John Innes Centre)

The transition to flowering is a fundamental switch in the plantlifecycle, which is reflected in its complex regulation. Genescontrolling the floral transition in the model plant Arabidopsisthaliana are grouped into 4 major pathways. A major integrator ofthese pathways is the gene FLOWERING LOCUS T (FT). Geneticapproaches have revealed most of the components necessary forflowering and how these interact. The floral switch also has anumber of dynamic properties, including commitment, tunabilityand the ability to integrate diverse environmental signals over time.To understand how the major regulators of the floral transitionmight confer these dynamic properties, we developed a mathema-tical model incorporating our current knowledge of the floraltransition. We initially sought to recreate the qualitative behaviourof the floral transition to verify whether our gene network structurewas capable of reproducing the expected switch-like behaviour. Byincluding new experimental data we were able to generate aquantitative model. Simulations we ran on flowering time mutantsor plants exposed to changing environmental conditions are inagreement with experimental data. This suggests our model

Abstracts / Comparative Biochemistry and Physiology, Part A 153 (2009) S195–S199 S197