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Role of Phytochromes in Shade Avoidance Ecophysiological and Molecular aspects

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Role of Phytochromes in Shade Avoidance Ecophysiological and Molecular aspects. Shade avoidance syndrome. Plants adapt to changes in light conditions -Shade Avoidance Syndrome-. photon fluence rate in 10 nm band centered on 660 nm photon fluence rate in 10 nm band centered on 730 nm.

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Presentation Transcript
slide3

Plants adapt to changes in light conditions

-Shade Avoidance Syndrome-

photon fluence rate in 10 nm

band centered on 660 nm

photon fluence rate in 10 nm

band centered on 730 nm

R/FR =

slide6

Phytochrome structure and chromophore

-Reception-

chromophore

phytochromobilin

PHY

holoprotein

PHY apoprotein

125 kDa monomer

Native phytochrome occurs as a dimer of 2 equivalent subunits

slide10

I. Subcellular partitioning

Phytochrome nucleocytoplasmic trafficking

good correlation between the wavelength requirement for physiological

responses and nuclear import of the different phytochromes

slide11

I. Subcellular partitioning

Phytochrome nucleocytoplasmic trafficking

phyA

minutes

phyB

hours

slide12

phyA

II. Proteolytic degradation

Phytochrome

slide13

The ubiquitin/26S proteasome pathway

major proteolytic pathway in plants and animals

slide15

Light signal transduction

-mutant analysis: light vs dark-

slide16

Long Hypocotyl 5 - HY5

long hypocotyl in R, FR and B

slide17

Phytochrome signal transduction

-cop/det/fus mutants-

slide18

COP/DET/FUS

name

Other protein

name

Function

Putative ubiquitin ligase component

COP1

DET1

COP10

COP16

COP11

FUS12

FUS11

COP8

FUS5

COP9

Protein required for HY5 degrad.

E2 Ub-conjugating enzymevariant

Not cloned

CSN1

CSN2

CSN3

CSN4

CSN7

CSN8

COP9 signalosome subunit

COP9 signalosome subunit

COP9 signalosome subunit

COP9 signalosome subunit

COP9 signalosome subunit

COP9 signalosome subunit

Phytochrome signal transduction

-cop/det/fus mutants-

slide19

F

Phytochrome signal transduction

- cop/det/fus mutants -

slide21

Phytochromes (PHY)

–responses to red and far-red light-

slide22

Phytochrome signal transduction

-more sophisticated screens: light quality-

Mutants that exhibit light-grown

characteristics in the dark

Mutants that exhibit altered seedling

development under specific light conditions

Wt phyA phyAspa1

Wt rsf1

e.g. Far-red light (phyA)

slide24

Phytochrome signal transduction

-proteolytic degradation-

slide25

Phytochrome signal transduction

-phytochrome interacting factors-

slide27

Isolation of Phytochrome Interacting Factor3

-a basic helix-loop-helixtranscription factor protein-

slide28

PIF3 negatively regulates phyB- but not phyA-

mediated inhibition of hypocotyl elongation

slide29

Phytochrome signal transduction

-bHLH class PIF3-like transcription factors-

slide30

III. Phosphorylation

-Phytochromes are similar to histidine kinases-

slide32

III. Phosphorylation

-Phytochrome Ser/Thr-kinase activity-

slide33

III. Phosphorylation

-phytochrome phosphorylation status; PAPP5-

slide34

III. Phosphorylation

-Phytochrome Ser/Thr-kinase activity; external targets-

slide35

Phytochrome signal transduction

-phosphorylation of phytochrome interacting factors-

slide36

IV. Regulation of transcription

phytochrome responses are associated with massive alterationsin gene expression

slide37

IV. Regulation of transcription

-Immediate phytochrome targets-

44% (far-red light) and 25% (red light) of early light-responsive genes (< 1 hr) encode transcription factors

slide38

IV. Regulation of transcription

-light/phytochrome responsive promoters-

slide40

Light regulated transcription factors

-post-transcriptional regulation; phosphorylation-

slide41

Light regulated transcription factors

post-transcriptional regulation;

phosphorylation, cellular localization

slide42

Light regulated transcription factors

-post-transcriptional regulation; degradation-

slide43

PIF3 as an example

cellular trafficking, gene expression, phosphorylation, degradation

slide44

Phytochrome signaling

Further downstream targets; phytohormones

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