Light-Activated Phytochrome A and B Interact with Members of the SPA Family to Promote Photomorphogenesis in Arabidopsis by Reorganizing the COP1/SPA Complex. Issue 1 (27th January 2015)

• Record Type: Journal Article
• Authors: Sheerin, David J.; Menon, Chiara; zur Oven-Krockhaus, Sven; Enderle, Beatrix; Zhu, Ling; Johnen, Philipp; Schleifenbaum, Frank; Stierhof, York-Dieter; Huq, Enamul; Hiltbrunner, Andreas
• Is Part Of: The Plant Cell. Volume 27:Issue 1(2015)
• Page Start: 189
• Page End: 201
• Publication Date: 2015-01-27
• DOI: 10.1105/tpc.114.134775
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : SPA proteins interact with phyA and phyB within nuclear bodies; light-induced binding of phyA and phyB to SPA proteins likely disrupts direct interaction of COP1 and SPAs, resulting in initiation of photomorphogenic development. 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.