Second positive phototropism results from coordinated co-action of the phototropins and cryptochromes.
Phototropism and hypocotyl growth inhibition are modulated by the coaction of different blue-light photoreceptors and their signaling pathways. How seedlings integrate the activities of the different blue-light photoreceptors to coordinate these hypocotyl growth responses is still unclear. We have used time-lapse imaging and a nontraditional mathematical approach to conduct a detailed examination of phototropism in wild-type Arabidopsis and various blue-light photoreceptor mutants. Our results indicate that high fluence rates of blue light (100 micro mol m(-)(2) s(-)(1)) attenuate phototropism through the coaction of the phototropin and cryptochrome blue-light photoreceptors. In contrast, we also demonstrate that phototropins and cryptochromes function together to enhance phototropism under low fluence rates (<1.0 micro mol m(-)(2) s(-)(1)) of blue light. Based on our results, we hypothesize that phototropins and cryptochromes regulate phototropism by coordinating the balance between stimulation and inhibition of growth of the hypocotyl depending on the fluence rate of blue light.
Whippo
Craig W
CW
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Hangarter
Roger P
RP
D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D017956:Photoreceptor Cells, Invertebrate; D018524:Phototropism / Q000528:radiation effects; D043562:Receptors, G-Protein-Coupled; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D013997:Time Factors
D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; C423903:PHOT2 protein, Arabidopsis; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila