Abstract
Phototropins (phot) are blue light receptors for phototropism, stomatal opening, and chloroplast relocation in angiosperms. To reveal the fundamental mechanisms of phot-mediated blue light responses, we used Marchantia polymorpha as a model plant. We analyzed the blue light responses of M. polymorpha and the structure of a PHOT gene in M. polymorpha. Firstly, as responses to blue light in M. polymorpha, we observed phototropism of thalli and protonemata, polarotropism of protonemata, and chloroplast relocation. By screening γ-irradiated spores, we obtained mutants about phototropism of protonemata. Secondly, we isolated a gene encoding phototropin (MpPHOT) in M. polymorpha. MpPHOT is present as a single copy, and grouped into the bryophyte PHOT clade. In addition, the transient expression of MpPHOT complemented the phenotype of chloroplast avoidance response in the phot2 mutant of the fern, Adiantum capillus-veneris. This suggested that Mpphot could function at least as a photoreceptor regulating the chloroplast avoidance response.
