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