title: An evolutionarily conserved signaling mechanism mediates far-red light responses in land plants.
abstract: Phytochromes are plant photoreceptors important for development and adaptation to the environment. Phytochrome A (PHYA) is essential for the far-red (FR) high-irradiance responses (HIRs), which are of particular ecological relevance as they enable plants to establish under shade conditions. PHYA and HIRs have been considered unique to seed plants because the divergence of seed plants and cryptogams (e.g., ferns and mosses) preceded the evolution of PHYA. Seed plant phytochromes translocate into the nucleus and regulate gene expression. By contrast, there has been little evidence of a nuclear localization and function of cryptogam phytochromes. Here, we identified responses to FR light in cryptogams, which are highly reminiscent of PHYA signaling in seed plants. In the moss Physcomitrella patens and the fern Adiantum capillus-veneris, phytochromes accumulate in the nucleus in response to light. Although P. patens phytochromes evolved independently of PHYA, we have found that one clade of P. patens phytochromes exhibits the molecular properties of PHYA. We suggest that HIR-like responses had evolved in the last common ancestor of modern seed plants and cryptogams and that HIR signaling is more ancient than PHYA. Thus, other phytochromes in seed plants may have lost the capacity to mediate HIRs during evolution, rather than that PHYA acquired it.
authors.affiliation: Centre for Plant Molecular Biology, University of Tübingen, 72076 Tuebingen, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Possart
authors.forename: Andreas
authors.initials: A
authors.lastname: Hiltbrunner
mesh_terms: D021581:Active Transport, Cell Nucleus; D035681:Adiantum / Q000166:cytology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites; D005075:Biological Evolution; D019068:Bryopsida / Q000166:cytology / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D002467:Cell Nucleus / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D008027:Light; D055537:Light Signal Transduction; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D055519:Photoreceptors, Plant / Q000235:genetics / Q000378:metabolism; D010834:Phytochrome / Q000235:genetics* / Q000378:metabolism; D051942:Phytochrome A / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins; D016415:Sequence Alignment; D031226:Sinapis / Q000166:cytology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; C441269:FHY1 protein, Arabidopsis; C497973:PHYA protein, Arabidopsis; D055519:Photoreceptors, Plant; D051942:Phytochrome A; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D010834:Phytochrome