Life on earth depends on light derived from the sun

Photosynthesis Light is required to help water reduce NADP+ PS2 680nm PS1 700 nm ATP NADPH Light energizes jumps in energy potential to get electrons run through an electron transfer chain H2OH2O2H + + 1/2O 2

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 Hypocotyl elongation Hypocotyl elongation Gene induction

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

darkbluered WT cry1 phyB cry1 : inhibition of hypocotyl elongation is insensitiv against blue light

darkblue 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 bacterial photolyase 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 hypocotyl elongation Open apical hook

closed apical hook Non-expanded cotyledons Etiolated hypocotyl Is skotomorphogenesis achived via active repression of photomorphogenesis

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

How to perform genetic approaches to decifer light regulation in plants ??? Photomorphogenesis in dark grown seedlings Skotomorphogenesis in light grown seedlings Asking simple questions

Getting complicated answers !! Short hypocotyl Expanded cotyledons Open apical hook

Skotomorphogenesis in the light

Functions of cop/det gene products COP1phytochrome chromophore biosynthesis DET1phytochrome B COP9phytochrome A DET2brassinosteroid biosynthesis

Dark Light wild-type cop/det mutants COP and DET proteins inhibit photomorphogenesis

Strasburger, 2002 Shade avoidance reaction