title: Light-dependent, dark-promoted interaction between Arabidopsis cryptochrome 1 and phytochrome B proteins.
abstract: Plant photoreceptors transduce environmental light cues to downstream signaling pathways, regulating a wide array of processes during growth and development. Two major plant photoreceptors with critical roles in photomorphogenesis are phytochrome B (phyB), a red/far-red absorbing photoreceptor, and cryptochrome 1 (CRY1), a UV-A/blue photoreceptor. Despite substantial genetic evidence for cross-talk between phyB and CRY1 pathways, a direct interaction between these proteins has not been observed. Here, we report that Arabidopsis phyB interacts directly with CRY1 in a light-dependent interaction. Surprisingly, the interaction is light-dissociated; CRY1 interacts specifically with the dark/far-red (Pr) state of phyB, but not with the red light-activated (Pfr) or the chromophore unconjugated form of the enzyme. The interaction is also regulated by light activation of CRY1; phyB Pr interacts only with the unstimulated form of CRY1 but not with the photostimulated protein. Further studies reveal that a small domain extending from the photolyase homology region (PHR) of CRY1 regulates the specificity of the interaction with different conformational states of phyB. We hypothesize that in plants, the phyB/CRY1 interaction may mediate cross-talk between the red/far-red- and blue/UV-sensing pathways, enabling fine-tuning of light responses to different spectral inputs.
authors.affiliation: Department of Biology, Duke University, Durham, North Carolina 27708, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hughes
authors.forename: Justin D
authors.initials: JD
authors.lastname: Vrana
authors.forename: Junqi
authors.initials: J
authors.lastname: Song
authors.forename: Chandra L
authors.initials: CL
authors.lastname: Tucker
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism* / Q000502:physiology*; D056931:Cryptochromes / Q000378:metabolism* / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D008027:Light; D008954:Models, Biological; D010786:Photoreceptor Cells / Q000378:metabolism; D051939:Phytochrome B / Q000378:metabolism*; D025941:Protein Interaction Mapping / Q000379:methods; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D014466:Ultraviolet Rays
chemical_list: D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D051939:Phytochrome B