title: Phytochrome A mediates rapid red light-induced phosphorylation of Arabidopsis FAR-RED ELONGATED HYPOCOTYL1 in a low fluence response.
abstract: Phytochrome A (phyA) is the primary photoreceptor for mediating the far-red high irradiance response in Arabidopsis thaliana. FAR-RED ELONGATED HYPOCOTYL1 (FHY1) and its homolog FHY1-LIKE (FHL) define two positive regulators in the phyA signaling pathway. These two proteins have been reported to be essential for light-regulated phyA nuclear accumulation through direct physical interaction with phyA. Here, we report that FHY1 protein is phosphorylated rapidly after exposure to red light. Subsequent exposure to far-red light after the red light pulse reverses FHY1 phosphorylation. Such a phenomenon represents a classical red/far-red reversible low fluence response. The phosphorylation of FHY1 depends on functioning phyA but not on other phytochromes and cryptochromes. Furthermore, we demonstrate that FHY1 and FHL directly interact with phyA by bimolecular fluorescence complementation and that both FHY1 and FHL interact more stably with the Pr form of phyA in Arabidopsis seedlings by coimmunoprecipitation. Finally, in vitro kinase assays confirmed that a recombinant phyA is able to robustly phosphorylate FHY1. Together, our results suggest that phyA may differentially regulate FHY1 and FHL activity through direct physical interaction and red/far-red light reversible phosphorylation to fine-tune their degradation rates and resulting light responses.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Conecticut 06520-8104, USA.
authors.forename: Yunping
authors.initials: Y
authors.lastname: Shen
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Zhou
authors.forename: Suhua
authors.initials: S
authors.lastname: Feng
authors.forename: Jigang
authors.initials: J
authors.lastname: Li
authors.forename: Anna
authors.initials: A
authors.lastname: Tan-Wilson
authors.forename: Li-Jia
authors.initials: LJ
authors.lastname: Qu
authors.forename: Haiyang
authors.initials: H
authors.lastname: Wang
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D056931:Cryptochromes; D005420:Flavoproteins / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D010766:Phosphorylation / Q000528:radiation effects; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051942:Phytochrome A / Q000502:physiology*; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; C524723:FHL protein, Arabidopsis; C441269:FHY1 protein, Arabidopsis; D005420:Flavoproteins; C497973:PHYA protein, Arabidopsis; D051942:Phytochrome A; D014157:Transcription Factors; D010834:Phytochrome