Abstract
In Arabidopsis thaliana, two phototropins, PHOT1 and PHOT2, function as blue light photoreceptors. Previously, we have proposed that phototropins might regulate the polar cell elongation in palisade tissue in response to blue light. In the phot1phot2 null mutant, palisade cells exhibit isotropic expansion rather than polar elongation in the leaf-thickness direction. Here, we investigated the effects of phot1 and phot2 on the polar cell elongation in palisade tissue. The phot2 mutant had stronger phenotype for the polar cell elongation than the phot1 mutant. In addition, the defect of phot1phot2 double mutant was completely rescued by 35S-PHOT2-GFP. Hence, phot2 played a major role to regulate the polar-cell elongation in palisade. We also asked where in the leaves phot2 perceives blue light to regulate the polarity of palisade-tissue cells. On the basis of those findings, relationship between the phot2 signals and their physiological consequences will be discussed.
