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A phytochrome/phototropin chimeric photoreceptor of fern functions as a blue/far‐red light‐dependent photoreceptor for phototropism in Arabidopsis
Author(s) -
Kanegae Takeshi,
Kimura Izumi
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12903
Subject(s) - phototropism , phototropin , phytochrome , fern , arabidopsis , biology , far red , blue light , protonema , botany , cryptochrome , biophysics , microbiology and biotechnology , red light , biochemistry , gene , physics , mutant , moss , circadian clock , optics
Summary In the fern Adiantum capillus‐veneris , the phototropic response of the protonemal cells is induced by blue light and partially inhibited by subsequent irradiation with far‐red light. This observation strongly suggests the existence of a phytochrome that mediates this blue/far‐red reversible response; however, the phytochrome responsible for this response has not been identified. PHY 3 / NEO 1 , one of the three phytochrome genes identified in Adiantum , encodes a chimeric photoreceptor composed of both a phytochrome and a phototropin domain. It was demonstrated that phy3 mediates the red light‐dependent phototropic response of Adiantum , and that phy3 potentially functions as a phototropin. These findings suggest that phy3 is the phytochrome that mediates the blue/far‐red response in Adiantum protonemata. In the present study, we expressed Adiantum phy3 in a phot1 phot2 phototropin‐deficient Arabidopsis line, and investigated the ability of phy3 to induce phototropic responses under various light conditions. Blue light irradiation clearly induced a phototropic response in the phy3‐expressing transgenic seedlings, and this effect was fully inhibited by simultaneous irradiation with far‐red light. In addition, experiments using amino acid‐substituted phy3 indicated that FMN ‐cysteinyl adduct formation in the light, oxygen, voltage ( LOV ) domain was not necessary for the induction of blue light‐dependent phototropism by phy3. We thus demonstrate that phy3 is the phytochrome that mediates the blue/far‐red reversible phototropic response in Adiantum . Furthermore, our results imply that phy3 can function as a phototropin, but that it acts principally as a phytochrome that mediates both the red/far‐red and blue/far‐red light responses.