1. Plant defense responses Hypersensitive response
Prepare a 10’ talk for Friday March 22 on plant defenses or describe interactions between plants & pathogens, pests or symbionts
Plant defense responses
Hypersensitive response
Systemic acquired resistance
Innate immunity
Phytoalexins
Defensins
Oxidative burst
Some possible pests
Nematodes
Rootworms
Aphids
Thrips
Gypsy moths
hemlock woolly adelgid
Some possible pathogens
Agrobacterium tumefaciens
Agrobacterium rhizogenes
Pseudomonas syringeae
Pseudomonas aeruginosa
Viroids
DNA viruses
RNA viruses
Fungi
Oomycetes
Some possible symbionts
N-fixing bacteria
N-fixing cyanobacteria
Endomycorrhizae
Ectomycorrhizae
Burkholderia ambifaria

2. Light regulation of Plant Development
Plants use light as food and information
Use information to control development

3. Light regulation of growth
Plants sense
Light quantity
Light quality (colors)
Light duration
Direction it comes from
Have photoreceptors
that sense specific
wavelengths

4. Types of Phytochrome Responses
3 classes based on fluence (amount of light needed)
VLF:induced by 0.1 nmol/m-2 , 50nmol/m-2
2. LF: induced by 1 µmol/m-2, µmol/m-2
3. HIR: require prolonged exposure to higher fluence
Different responses = Different phytochromes

5. Types of Phytochrome Responses
PHYA mediates VLF and HIR due to FR
Very labile in light
2. PHYB mediates LF and HIR due to R
Stable in light
3. Roles of PHYs C, D & E not so clear

6. Types of Phytochrome Responses
PHYA & PHYB are often antagonistic.
In sunlight PHYB mainly controls development
In shade PHYA 1st controls development, since FR is high
But PHYA is light-labile; PHYB takes over & stem grows
"shade-avoidance"

7. Phytochrome
Pr has cis-chromophore
Red converts it to trans = active shape
Far-red reverts it to cis

8. Phytochrome
some stay in cytoplasm & activate ion pumps
Rapid responses are due to changes in ion fluxes
most enter nucleus and kinase transcription factors
Slow responses are due to changes in gene expression

9. Phytochrome
most enter nucleus and kinase transcription factors
Slow responses are due to changes in gene expression
Many targets of PHY are transcription factors, eg PIF3
Activate cascades of genes for photomorphogenesis

10. Phytochrome
Protein degradation is important for light regulation
Cop mutants can’t degrade specific proteins
COP1/SPA targets specific TF for degradation
DDA1/DET1/COP10 target other proteins
Other COPs form part of COP9 signalosome
W/O COPs these TF act in dark

11. Circadian rhythms
Many plant responses, some developmental, some physiological, show circadian rhythms
Leaves move due to circadian ion fluxes in/out of dorsal & ventral motor cells

12. Circadian rhythms
Many plant responses show circadian rhythms
Once entrained, continue in constant dark

13. Circadian rhythms
Many plant responses show circadian rhythms
Once entrained, continue in constant dark, or constant light

14. Circadian rhythms
Many plant responses show circadian rhythms
Once entrained, continue in constant dark, or constant light!
Gives plant headstart on photosynthesis, other processes that need gene expression

15. Circadian rhythms
Many plant responses show circadian rhythms
Once entrained, continue in constant dark, or constant light!
Gives plant headstart on photosynthesis, other processes that need gene expression
eg elongation at night!

16. Circadian rhythms
Gives plant headstart on photosynthesis, other processes that need gene expression
eg elongate at night!
Endogenous oscillator is temperature-compensated, so runs at same speed at all times

17. Circadian rhythms
Endogenous oscillator is temperature-compensated, so runs at same speed at all times
Is a negative feedback loop of transcription-translation
Light & TOC1 activate LHY & CCA1 at dawn

18. Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too

19. Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)

20. Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Phytochrome entrains the clock

21. Circadian rhythms
Light & TOC1 activate LHY & CCA1 at dawn
LHY & CCA1 repress TOC1 in day, so they decline too
At night TOC1 is activated (not enough LHY & CCA1)
Phytochrome entrains the clock So does blue light

22. Blue Light Responses
Circadian Rhythms

23. Blue Light Responses
Circadian Rhythms
Solar tracking

24. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism

25. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation

26. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement

27. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement
Stomatal opening

28. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement
Stomatal opening
Gene expression

29. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement
Stomatal opening
Gene expression
Flowering in Arabidopsis

30. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement
Stomatal opening
Gene expression
Flowering in Arabidopsis
Responses vary in their fluence requirements

31. Blue Light Responses
Circadian Rhythms
Solar tracking
Phototropism
Inhibiting stem elongation
Chloroplast movement
Stomatal opening
Gene expression
Flowering in Arabidopsis
Responses vary in their fluence requirements & lag times

32. Blue Light Responses
Responses vary in their fluence requirements & lag time
Stomatal opening is reversible by green light; others aren’t

33. Blue Light Responses
Responses vary in their fluence requirements & lag time
Stomatal opening is reversible by green light; others aren’t
Multiple blue receptors with
different functions!

34. Blue Light Responses
Responses vary in their fluence requirements & lag time
Stomatal opening is reversible by green light; others aren’t
Multiple blue receptors with
different functions!
Identified by mutants

35. Blue Light Responses
Responses vary in their fluence requirements & lag time
Stomatal opening is reversible by green light; others aren’t
Multiple blue receptors with
different functions!
Identified by mutants, then clone
the gene and identify the protein

36. Blue Light Responses
Responses vary in their fluence requirements & lag time
Stomatal opening is reversible by green light; others aren’t
Multiple blue receptors with
different functions!
Identified by mutants, then clone
the gene and identify the protein
Cryptochromes repress hypocotyl
elongation

37. Blue Light Responses
Cryptochromes repress hypocotyl elongation
Stimulate flowering

38. Blue Light Responses
Cryptochromes repress hypocotyl elongation
Stimulate flowering
Set the circadian clock (in humans, too!)

39. Blue Light Responses
Cryptochromes repress hypocotyl elongation
Stimulate flowering
Set the circadian clock (in humans, too!)
Stimulate anthocyanin synthesis

40. Blue Light Responses
Cryptochromes repress hypocotyl elongation
Stimulate flowering
Set the circadian clock (in humans, too!)
Stimulate anthocyanin synthesis
3 CRY genes

41. Blue Light Responses
3 CRY genes
All have same basic structure:
Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase
(an enzyme that uses light energy to repair pyr dimers)

42. Blue Light Responses
3 CRY genes
All have same basic structure:
Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase
(an enzyme that uses light energy to repair pyr dimers)
DAS binds COP1 & has nuclear localization signals

43. Blue Light Responses
3 CRY genes
All have same basic structure:
Photolyase-like domain binds FAD and a pterin (MTHF) that absorbs blue & transfers energy to FAD in photolyase
(an enzyme that uses light energy to repair pyr dimers)
DAS binds COP1 & has nuclear localization signals
CRY1 & CRY2 kinase proteins after absorbing blue

44. Blue Light Responses
3 CRY genes
CRY1 & CRY2 kinase proteins after absorbing blue
CRY3 repairs mt & cp DNA!

45. Blue Light Responses
3 CRY genes
CRY1 regulates blue effects on growth: light-stable
Triggers rapid changes in PM potential & growth

46. Blue Light Responses
3 CRY genes
CRY1 regulates blue effects on growth: light-stable
Triggers rapid changes in PM potential & growth
Opens anion channels in PM

47. Blue Light Responses
3 CRY genes
CRY1 regulates blue effects on growth: light-stable
Triggers rapid changes in PM potential & growth
Opens anion channels in PM
Stimulates anthocyanin synthesis