stress responses & gene expression plants must adapt to stresses because of their sedentary...
TRANSCRIPT
![Page 1: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/1.jpg)
Stress Responses & Gene Expression
• plants must adapt to stresses because of their sedentary lifestyle
Fig. 22.2, Buchanan et al.
![Page 2: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/2.jpg)
Adaptation versus Acclimation
• Adaptation - evolutionary changes that enable an organism to exploit a certain niche. These include modification of existing genes, as well as gain/loss of genes.– e.g., thermo-stable enzymes in organisms that
tolerate high temperature
• Acclimation – inducible responses that enable an organism to tolerate an unfavorable or lethal change in their environment.– e.g., heat shock response
![Page 3: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/3.jpg)
Types of Stress
Abiotic 1. heat
2. cold 3. drought 4. salt
5. wind 6. oxidative 7. anaerobic 8. heavy metals 9. nutrient deprivation10. excessive light
Biotic
1.pathogens
2.herbivores
![Page 4: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/4.jpg)
Plants respond to stresses as individual cells and as whole organisms – stress induced signals can be transmitted throughout the plant, making other parts more ready to withstand the stress..
Fig. 22.3, Buchanan et al.
![Page 5: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/5.jpg)
Most organisms are adapted to environmental temperature:
1. Psychrophiles (< 20 °C)
2. Mesophiles (~ 20-35 °C)
3. Thermophiles ( ~35-70 °)
4. Hyperthermophiles (70-110 °C)
Groups 1,3 & 4 are a.k.a. “Extremophiles”
But can also acclimate to “extreme” shifts, if they are not permanent, and not too extreme.
Two well studied acclimation responses are:1. the Heat Shock response2. Cold acclimation
![Page 6: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/6.jpg)
Heat Stress (or Heat Shock) Response
• Induced by temperatures ~10-15oC above normal • Ubiquitous (conserved), rapid & transient• Dramatic change in pattern of protein synthesis
– induction (increase) of HSPs– most HSPs are chaperones (chaperonins) that
promote protein re-folding & stability• HSP induction mediated by a bZIP factor, HSF
Fig. 22.43, Buchanan et al.
![Page 7: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/7.jpg)
28oC 40oC 45oC 45oC
Fig. 22.42, Buchanan et al.Soybean seedlings.
Thermotolerant growth of soybean seedlings following a heat shock.
![Page 8: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/8.jpg)
Heat stress effects on protein synthesis in soybean seedlings (J. Key).
Joe Key
![Page 9: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/9.jpg)
Cold Acclimation (CA) involves:• Increased accumulation of small solutes
– retain water & stabilize proteins– e.g., proline, glycine betaine, trehalose
• Altered membrane lipids, to lower gelling temp.• Changes in gene expression [e.g., antifreeze proteins,
proteases, RNA-binding proteins (?)]• Many cold-regulated promoters have DRE/C-elements
• Activated by CBF1 transcription factor
![Page 10: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/10.jpg)
Role of ABA (stress hormone)
• ABA – Abscisic acid, phytohormone induced by wilting, closes stomata by acting on guard cells
• Positive correlation between CA and
[ABA]
• Treat plants with ABA, and they will be somewhat cold hardened
However, ABA does not induce all genes that cold will.
Conclusion: there are ABA-regulated and non-ABA regulated changes that are induced by cold.
![Page 11: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/11.jpg)
Plants vary in ability to tolerate flooding
Plants can be classified as:
• Wetland plants (e.g., rice, mangroves)• Flood-tolerant (e.g., Arabidopsis,
maize)• Flood-sensitive (e.g., soybeans,
tomato)
Involves developmental/structural, cellular and molecular adaptations.
Pneumatophores in mangrove
![Page 12: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/12.jpg)
Flooding causes anoxia and an anaerobiotic response in roots.
Maize (corn)
Fig. 22.23
- Shift carbohydrate metabolism from respiration to anaerobic glycolysis
- Protein synthesis affected: results in selective synthesis of ~10-20 proteins
-mRNAs for other proteins there but not translated well!
Most of the ANPs are enzymes associated with glycolysis and fermentation.
![Page 13: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/13.jpg)
Fig. 22.30
Protein synthesis in aerobic versus anoxic maize root tips.5-hour labeling with 3H-leucine and 2-D gel electrophoresis.
Aerobic Anoxic
![Page 14: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/14.jpg)
Enzymes that are up-regulated by anaerobiosis
![Page 15: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/15.jpg)
Biotic Stress and Plant Defense Responses
Pathogen Strategies
1. Necrotrophic – plant tissue killed and then colonized; broad host range
e.g., rotting bacteria (Erwinia)
2. Biotrophic – plant cells remain alive, narrow host range (1 plant species)
e.g., viruses, nematodes, fungal mildews
![Page 16: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/16.jpg)
Major PathogensViruses - most are RNA viruses w/small
genomes, which always encode: 1. Coat protein2. RNA-dependent RNA polymerase
3. Movement protein(s)
Viroids – naked, single strands of RNA; discovered by T.O. Diener
Bacteria- e.g., Xanthomonas
Fungi - 4 major groups
Nematodes - root parasites, also increase infection by microorganisms
ds DNA virus:Cauliflower Mosaic Virus
SS RNA virus: Tobacco Mosaic Virus
Fig. 21.10, Buchanan et al.
![Page 17: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/17.jpg)
Plant Defenses
1) Physical barriers: cuticle, thorns, cell walls
2) Constitutively produced chemicals (e.g., phytoalexins) and proteins (e.g., Ricin)
3) Induced responses (a.k.a., the Plant Defense Response)
![Page 18: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/18.jpg)
The Plant Defense Response
3 aspects of response:
1. Hypersensitive
2. Local
3. Systemic
Compatible interaction diseaseIncompatible interaction resistance
![Page 19: Stress Responses & Gene Expression plants must adapt to stresses because of their sedentary lifestyle Fig. 22.2, Buchanan et al](https://reader030.vdocuments.us/reader030/viewer/2022032523/56649d8a5503460f94a7016f/html5/thumbnails/19.jpg)
Distribution of Oak Wilt in the US
Fungus - Ceratocystis fagacearum
Leaves from Infected tree
Natural root grafts Sap beetle