title: Light-activated phytochrome A and B interact with members of the SPA family to promote photomorphogenesis in Arabidopsis by reorganizing the COP1/SPA complex.
abstract: Phytochromes function as red/far-red photoreceptors in plants and are essential for light-regulated growth and development. Photomorphogenesis, the developmental program in light, is the default program in seed plants. In dark-grown seedlings, photomorphogenic growth is suppressed by the action of the CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)/SUPPRESSOR OF phyA-105 (SPA) complex, which targets positive regulators of photomorphogenic growth for degradation by the proteasome. Phytochromes inhibit the COP1/SPA complex, leading to the accumulation of transcription factors promoting photomorphogenesis; yet, the mechanism by which they inactivate COP1/SPA is still unknown. Here, we show that light-activated phytochrome A (phyA) and phytochrome B (phyB) interact with SPA1 and other SPA proteins. Fluorescence resonance energy transfer-fluorescence lifetime imaging microscopy analyses show that SPAs and phytochromes colocalize and interact in nuclear bodies. Furthermore, light-activated phyA and phyB disrupt the interaction between COP1 and SPAs, resulting in reorganization of the COP1/SPA complex in planta. The light-induced stabilization of HFR1, a photomorphogenic factor targeted for degradation by COP1/SPA, correlates temporally with the accumulation of phyA in the nucleus and localization of phyA to nuclear bodies. Overall, these data provide a molecular mechanism for the inactivation of the COP1/SPA complex by phyA- and phyB-mediated light perception.
authors: Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
authors: David J
authors: DJ
authors: Sheerin
authors: Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany.
authors: Chiara
authors: C
authors: Menon
authors: Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany.
authors: Sven
authors: S
authors: zur Oven-Krockhaus
authors: Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
authors: Beatrix
authors: B
authors: Enderle
authors: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712.
authors: Ling
authors: L
authors: Zhu
authors: Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany.
authors: Philipp
authors: P
authors: Johnen
authors: Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany.
authors: Frank
authors: F
authors: Schleifenbaum
authors: Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany.
authors: York-Dieter
authors: YD
authors: Stierhof
authors: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712.
authors: Enamul
authors: http://orcid.org/0000-0001-7692-5139
authors: E
authors: Huq
authors: Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany andreas.hiltbrunner@biologie.uni-freiburg.de.
authors: Andreas
authors: A
authors: Hiltbrunner
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D018506:Gene Expression Regulation, Plant; D051942:Phytochrome A / Q000378:metabolism*; D051939:Phytochrome B / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D029681:Arabidopsis Proteins; D051942:Phytochrome A; D051939:Phytochrome B
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