Plant photoreceptors and their signaling components compete for COP1 binding via VP peptide motifs

First author: Kelvin Lau; Affiliations: University of Geneva (日内瓦大学): Geneva, Switzerland

Corresponding author: Michael Hothorn

Plants sense different parts of the sun's light spectrum using distinct photoreceptors, which signal through the E3 ubiquitin ligase COP1. Here, we analyze why many COP1‐interacting transcription factors and photoreceptors harbor sequence‐divergent Val‐Pro (VP) motifs that bind COP1 with different binding affinities. Crystal structures of the VP motifs of the UV‐B photoreceptor UVR8 and the transcription factor HY5 in complex with COP1, quantitative binding assays, and reverse genetic experiments together suggest that UVR8 and HY5 compete for COP1. Photoactivation of UVR8 leads to high‐affinity cooperative binding of its VP motif and its photosensing core to COP1, preventing COP1 binding to its substrate HY5. UVR8–VP motif chimeras suggest that UV‐B signaling specificity resides in the UVR8 photoreceptor core. Different COP1–VP peptide motif complexes highlight sequence fingerprints required for COP1 targeting. The blue‐light photoreceptors CRY1 and CRY2 also compete with transcription factors for COP1 binding using similar VP motifs. Thus, our work reveals that different photoreceptors and their signaling components compete for COP1 via a conserved mechanism to control different light signaling cascades.

植物利用不同的光受体来感受太阳光的不同光谱，这些信号都会通过E3泛素连接酶COP1。本文中，作者分析了为何许多COP1互作转录因子与光受体会存在序列分化的VP基序，该基序可以结合COP1，但亲和力不一。对于与COP形成复合物的UV‐B光受体UVR8和转录因子HY5上的VP基序的晶体结构解析、定量结合试验、反向遗传学试验显示UVR8和HY5会竞争COP1。UVR8的光激活会导致其VP基序具有高度亲和的结合能力，同时在其结合到COP1上时会阻止COP1结合其底物HY5。UVR8–VP基序嵌合体显示UVR8光受体核心中存在UV‐B信号转导特异性。不同的COP1–VP多肽基序复合物绘制出了一幅COP1靶向序列的指纹图谱。蓝光受体CRY1和CRY2同样能够通过类似的VP基序与转录因子竞争结合COP1。因此，作者的研究揭示了不同的光受体及其信号转导组分通过一个保守的机制相互竞争结合COP1，从而控制不同的光信号级联。

通讯：Michael Hothorn (https://biveg.unige.ch/labs/hothorn/)

个人简介：1998-2002年， 德国海德堡大学，生物学专业学士；2002-2006年，欧洲分子生物学实验室，结构生物学博士；2007-2011年，索尔克研究所，博士后。

研究方向：植物细胞膜信号转导；肌醇焦磷酸和无机多磷酸盐的代谢和信号传导。

doi: https://doi.org/10.1093/jxb/erz287

Journal: The EMBO Journal

Published date: July 15, 2019