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

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

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

Types of Phytochrome Responses 3 classes based on fluence (amount of light needed) VLF:induced by 0.1 nmol/m-2 , saturate @ 50nmol/m-2 2. LF: induced by 1 µmol/m-2, saturate @ 1000 µmol/m-2 3. HIR: require prolonged exposure to higher fluence Different responses = Different phytochromes

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

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"

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

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

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

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

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

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

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

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

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!

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

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

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

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)

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

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

Blue Light Responses Circadian Rhythms

Blue Light Responses Circadian Rhythms Solar tracking

Blue Light Responses Circadian Rhythms Solar tracking Phototropism

Blue Light Responses Circadian Rhythms Solar tracking Phototropism Inhibiting stem elongation

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

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

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

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

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

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

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

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!

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

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

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

Blue Light Responses Cryptochromes repress hypocotyl elongation Stimulate flowering

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

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

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

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)

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

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

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

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

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

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