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
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