title: Phosphorylation of FAR-RED ELONGATED HYPOCOTYL1 is a key mechanism defining signaling dynamics of phytochrome A under red and far-red light in Arabidopsis.
abstract: Emerging plants have to adapt to a high ratio of far-red light (FR)/red light (R) light in the canopy before they reach the R-enriched direct sunlight. Phytochrome A (phyA) is the single dominant photoreceptor in young Arabidopsis thaliana seedlings that initiates photomorphogenesis in response to a FR-enriched environment and transduces increasing R signals to early responsive genes. To date, how phyA differentially transmits FR and R signals to downstream genes remains obscure. Here, we present a phyA pathway in which FAR-RED ELONGATED HYPOCOTYL1 (FHY1), an essential partner of phyA, directly guides phyA to target gene promoters and coactivates transcription. Furthermore, we identified two phosphorylation sites on FHY1, Ser-39 and Thr-61, whose phosphorylation by phyA under R inhibits phyA signaling at each step of its pathway. Deregulation of FHY1 phosphorylation renders seedlings colorblind to FR and R. Finally, we show that the weaker phyA response resulting from FHY1 phosphorylation ensures the seedling deetiolation process in response to a R-enriched light condition. Collectively, our results reveal FHY1 phosphorylation as a key mechanism for FR/R spectrum-specific responses in plants and an essential event for plant adaption to changing light conditions in nature.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Conecticut 06520, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Chen
authors.forename: Xiarong
authors.initials: X
authors.lastname: Shi
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Mingqiu
authors.initials: M
authors.lastname: Dai
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yunping
authors.initials: Y
authors.lastname: Shen
authors.forename: Jigang
authors.initials: J
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D008027:Light; D010766:Phosphorylation / Q000528:radiation effects; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; C441269:FHY1 protein, Arabidopsis; D010834:Phytochrome