Life on earth depends on light derived from the sun

Photosynthesis

Light is required to help water reduce NADP+

PS2680nm

PS1700 nm

ATP

NADPH

Light energizes jumps in energy potentialto get electrons run through anelectron transfer chain

H2O 2H+ + 1/2O2

Engelmann experiment

What is an action

spectrum??

And what is an absorption spectrum??

Action spectrum vs. absorption spectrum

Directionality of blue light induced bending

(Action spectrum)

Directionality of blue light induced bending

Kinetics of blue light effects

Membrane depolarization

Hypocotylelongation

Hypocotylelongation

Gene induction

Stomata opening regulated by blue light

Stomata opening regulated by blue light

Protoplasts

dark

Protoplasts

blue light

Measuring irradiation:

chloroplast movements (Lemna) depending

on light intensity

Dunkelheit Schwachlicht Starklicht

Blue light induced bending of coleoptiles

phot1 (phototropin1)

blue light

wild-type

phot1 mutant

PHOT genes in Arabidopsis

LOV-domains are flavin binding sites (FMN)

LOV-domains change redox status in proteins through (Light, Oxygen, Voltage)

Phototropism chloroplast stomata movement opening

cryptochrome, together with phytochromes

deetiolation of seedlings

photoperiodic induced morphoses (e.g. flower induction)

circadian rhythms

dark blue red

WT cry1 phyB WT cry1 phyB WT cry1 phyB

cry1 : inhibition of hypocotyl elongation is insensitiv against blue light

dark blue

WT cry1 phyB WT cry1 phyB

cry1 : analysis of cry1 mutants and over-producers

MTHF (pterin)

8-HDF (deazaflavin)

FADH-

CRY1 shows similarity to prokaryotic DNA photolyases

CRY1

bacterialphotolyase

70% 70%30%

Chromophor 1: Chromophor 2:

SKOTOMORPHOGENESIS

Photomorphogenesis Skotomorphogenesis

SKOTOMORPHOGENESIS

Skotomorphogenesis

Light has an influence on seedling development

Photomorphogenesis Skotomorphogenesis

Hypocotyl: long short

Apical hook: closed open

Cotyledons: closed expanded

Chloroplasts: proplastids fully developed

Photosynthesis: no yes

Cotyledon expansion

Reduced hypocotylelongation

Open apical hook

closed apical hook Non-expanded

cotyledons

Etiolated hypocotyl

Is skotomorphogenesis achived via active repression of photomorphogenesis

How to perform genetic approaches todecifer light regulation in plants ???

How to perform genetic approaches todecifer light regulation in plants ???

Photomorphogenesisin dark grown seedlings

Skotomorphogenesis in light grown seedlings

Asking simple questions

Getting complicated answers !!

Shorthypocotyl

Expanded cotyledons

Open apical hook

Skotomorphogenesis in the light

Functions of cop/det gene products

COP1 phytochrome chromophore biosynthesis

DET1 phytochrome B

COP9 phytochrome A

DET2 brassinosteroid biosynthesis

Dark

Light

wild-type

cop/detmutants

COP and DET proteins inhibit photomorphogenesis

Strasburger, 2002

Shade avoidance reaction