BLUE LIGHT RESPONSESBLUE LIGHT RESPONSES

1.1. PhotoropismPhotoropism

2.2. Inhibition of stem stem and hypocotyl elongationInhibition of stem stem and hypocotyl elongation

3.3. Stimulation of chlorophyll and carotenoid synthesisStimulation of chlorophyll and carotenoid synthesis

4.4. Stomatal openingStomatal opening

5.5. Chloroplast movementsChloroplast movements

6.6. Anthocyanin synthesisAnthocyanin synthesis

ACTION SPECTRUM

Blue light inhibition of elongation

Blue light stimulation of glutamate semialdehyde aminotransferase, an enzyme involved in chlorophyll synthesis

CHLOROPLAST MOVEMENTS -CHLOROPLAST MOVEMENTS -LEMNALEMNA

DARK WEAK BLUE LIGHT STRONG BLUE LIGHT

DARKDARK

BLUE LIGHTBLUE LIGHT

CLOSE CORRELATION BETWEEN LIGHT AND STOMATAL OPENING

BLUE LIGHT PHOTORECEPTORSBLUE LIGHT PHOTORECEPTORS

1.1. PHOTOTROPINS : PHOTOTROPINS : phot1phot1 and and phot2phot2

- SERVE AS THE BLUE LIGHT SERVE AS THE BLUE LIGHT PHOTORECEPTORS FOR PHOTOTROPISM, PHOTORECEPTORS FOR PHOTOTROPISM, CHLOROPLAST MOVEMEMNTS, AND CHLOROPLAST MOVEMEMNTS, AND STOMATAL OPENINGSTOMATAL OPENING

- MUTANTS LACK BLUE LIGHT DEPENDENT MUTANTS LACK BLUE LIGHT DEPENDENT PHOTOTROPISM, CHLOROPLAST PHOTOTROPISM, CHLOROPLAST MOVEMENTS, AND STOMATAL OPENINGMOVEMENTS, AND STOMATAL OPENING

- PHOTOTROPINS ARE FLAVOPROTEINS WITH PHOTOTROPINS ARE FLAVOPROTEINS WITH SER/THR PROTEIN KINASES THAT SER/THR PROTEIN KINASES THAT AUTOPHOSPHORYLATE IN RESPONSE TO AUTOPHOSPHORYLATE IN RESPONSE TO BLUE LIGHTBLUE LIGHT

BLUE LIGHT PHOTORECEPTORS (CONT.)BLUE LIGHT PHOTORECEPTORS (CONT.)

2. CRYPTOCHROMES (2. CRYPTOCHROMES (cry1cry1 and and cry2cry2))

- CRYPTOCHROMES PLAY ROLES IN BLUE-LIGHT-CRYPTOCHROMES PLAY ROLES IN BLUE-LIGHT-MEDIATED GROWTH INHIBITION. MUTANTMEDIATED GROWTH INHIBITION. MUTANT HYPOCOTYLS ARE NOT INHIBITED BY BLUE LIGHT.HYPOCOTYLS ARE NOT INHIBITED BY BLUE LIGHT.

- HOWEVER, NO PHOTOCHEMISTRY HAS YET BEEN HOWEVER, NO PHOTOCHEMISTRY HAS YET BEEN DEMONSTRATED, AND SO THEY MAY NOT ACT AS DEMONSTRATED, AND SO THEY MAY NOT ACT AS PHOTORECEPTORSPHOTORECEPTORS

- CRYPTOCHROMES ALSO FOUND IN ANIMAL CELLS CRYPTOCHROMES ALSO FOUND IN ANIMAL CELLS WHERE THEY FUNCTION IN CIRCADIAN RHYTHMS, WHERE THEY FUNCTION IN CIRCADIAN RHYTHMS, BUT DO NOT ACT AS PHOTORECEPTORSBUT DO NOT ACT AS PHOTORECEPTORS

- CRYPTOCHROMES MAY BE INVOLVED IN SIGNAL CRYPTOCHROMES MAY BE INVOLVED IN SIGNAL TRANSDUCTION DOWNSTREAM OF OTHER BLUE TRANSDUCTION DOWNSTREAM OF OTHER BLUE LIGHT PHOTORECEPTORS.LIGHT PHOTORECEPTORS.

BLUE LIGHT PHOTORECEPTORS (CONT.)BLUE LIGHT PHOTORECEPTORS (CONT.)

3.3. ZEAXANTHIN - CAROTENOID LOCATED IN THE ZEAXANTHIN - CAROTENOID LOCATED IN THE CHLOROPLASTCHLOROPLAST

- MAY REGULATE STOMATAL OPENING. MUTANTS - MAY REGULATE STOMATAL OPENING. MUTANTS HAVE REDUCED RESPONSE TO BLUE LIGHT.HAVE REDUCED RESPONSE TO BLUE LIGHT.

- ZEAXANTHINS AND PHOTOROPINS MAY WORK - ZEAXANTHINS AND PHOTOROPINS MAY WORK TOGETHER IN GUARD CELLSTOGETHER IN GUARD CELLS

ZEAXANTHIN CAN UNDERO A CIS-TRANS ZEAXANTHIN CAN UNDERO A CIS-TRANS ISOMERIZATIONISOMERIZATION

Trans-Zeaxanthin Cis-ZeaxanthinBLUE

GREEN

(THIS MODEL IS STILL HYPOTHETICAL)