Photomorphogenesis Skotomorphogenesis(etiolation)

Light has an influence on seedling development

Photomorphogenesis

inhibition of hypocotyl elongation

opening of apical hook

cotyledon expansion

chloroplast development

Dark Light

Dark

Light

wild-type

cop/detmutants

COP and DET proteins inhibit photomorphogenesis

Development (realization of a phenotype from a genotype)

is controlled by

endogenous factors

intercellular regulation

phytohormones

exogenous factors

biotic factors

abiotic factors

Germination of lettuce seeds (photoreversibility)

Reversible R/FR response system controlled by phytochrome

germination germination

Pr PfrRed light

Far-red light

inactive active

Phytochrome dogma

synthesisgermination,flower Induction……

red light

far red light

Phytochrome: from synthesis to action

blue light red light

Arabidopsis: 5 phytochrome proteins (phyA - phy E),

differ in their apoproteins

Phytochrome: homodimeric chromoprotein:

apoprotein and phytochromobilin (open chained tetrapyrrol) as chromophor form holoprotein

Strasburger, 2002

R FR

PRinactive

PFRactive

PFR

active

PR

inactive

sensor signal transduction

Regulatory function

Strasburger, 2002

Structure of phytochrome proteins

N-terminal extension

Hinge region

PAS domain

Histidine kinase related 1

Histidine kinase related 2

Chromophore binding domain

The Phytochrome apoprotein (-chromophore) is a 125kD monomer

Chromophore binding domains

Two holoproteins (+chromophore) form a dimer

IIAIA

IIBIB

Red light

Far-red light

PrPfr

Two holoproteins (+chromophore) form a dimer

Histidine kinase related

Chromophore binding domain

IIAIA

IIBIB

IA IIA

IIBIB

Phytochrome responses vary with amount of light

VLFR: 0.00001 µmol x m-2

LFR: 1-1000 µmol x m-2

Arabidopsis seed germination

Lettuce seed germination

Anthocyanin synthesisInhibition of hypocotyl elong.Enlargement of cotyledonsApical hook opening

HIR: >1000 µmol x m-2 x s-1

Phytochrome responses vary with amount of light

Inhibition of hypocotyl elongation

HIR: >1000 µmol x m-2 x s-1

Phytochrome responses vary with amount of light

LFR: 1-1000 µmol x m-2

Lettuce seed germination

Strasburger, 2002

Shade avoidance reaction

Strasburger, 2002

Shade avoidance reaction

Strasburger, 2002

Shade avoidance reaction

Figure 17.9 Phytochrome is an autophosphorylating protein

kinase

PHYA-GFP and PHYB-GFP fusion proteins migrate into the nucleus

PHYA-GFP

PHYB-GFP

Dark Red

Dark Red