A phyB-PIF1-SPA1 kinase regulatory complex promotes photomorphogenesis in Arabidopsis.

Inyup Paik, Fulu Chen, Vinh Ngoc Pham, Ling Zhu, Jeong-Il Kim, Enamul Huq

Nature communications 2019 Sep 16

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CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) is a highly conserved E3 ubiquitin ligase from plants to animals and acts as a central repressor of photomorphogenesis in plants. SUPPRESSOR OF PHYA-105 1 family members (SPA1-SPA4) directly interact with COP1 and enhance COP1 activity. Despite the presence of a kinase domain at the N-terminus, no COP1-independent role of SPA proteins has been reported. Here we show that SPA1 acts as a serine/threonine kinase and directly phosphorylates PIF1 in vitro and in vivo. SPAs are necessary for the light-induced phosphorylation, ubiquitination and subsequent degradation of PIF1. Moreover, the red/far-red light photoreceptor phyB interacts with SPA1 through its C-terminus and enhances the recruitment of PIF1 for phosphorylation. These data provide a mechanistic view on how the COP1-SPA complexes serve as an example of a cognate kinase-E3 ligase complex that selectively triggers rapid phosphorylation and removal of its substrates, and how phyB modulates this process to promote photomorphogenesis.

Citation

Inyup Paik, Fulu Chen, Vinh Ngoc Pham, Ling Zhu, Jeong-Il Kim, Enamul Huq. A phyB-PIF1-SPA1 kinase regulatory complex promotes photomorphogenesis in Arabidopsis. Nature communications. 2019 Sep 16;10(1):4216