COP1 positively regulates ABA signaling during Arabidopsis seedling growth in darkness by mediating ABA-induced ABI5 accumulation

第一作者：Jing Peng

第一单位：中国农业大学

第一通讯：Jigang Li

 Abstarct 

背景回顾：CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), a well-characterized E3 ubiquitin ligase, is a central repressor of seedling photomorphogenic development in darkness. 

COP1是一个研究得比较透彻的E3泛素连接酶，是黑暗中幼苗光形态发育的核心抑制因子。

提出问题：However, whether COP1 is involved in modulating abscisic acid (ABA) signaling in darkness remains largely obscure. 

但是，COP1是否参与黑暗中ABA信号转导的调控还不清楚。

主要发现：Here, we report that COP1 is a positive regulator of ABA signaling during Arabidopsis seedling growth in the dark. 

本文中，作者报道了黑暗条件下拟南芥幼苗生长时ABA信号转导的正向调控因子。

结果1：COP1 mediates ABA-induced accumulation of ABI5, a transcription factor playing a key role in ABA signaling, through transcriptional and post-translational regulatory mechanisms. 

COP1通过转录和翻译后的调节机制介导ABA诱导的ABI5积累，ABI5是一个在ABA信号转导中起关键作用的转录因子。

结果2：We further show that COP1 physically interacts with ABA-hypersensitive DCAF1 (ABD1), a substrate receptor of the CUL4-DDB1 E3 ligase targeting ABI5 for degradation. Accordingly, COP1 directly ubiquitinates ABD1 in vitro, and negatively regulates ABD1 protein abundance in vivo in the dark but not in the light. Therefore, COP1 promotes ABI5 protein stability post-translationally in darkness by destabilizing ABD1 in response to ABA. Interestingly, we reveal that ABA induces the nuclear accumulation of COP1 in darkness, thus enhancing its activity in propagating the ABA signal. 

作者的进一步研究表明COP1能够与ABD1发生物理互作，而后者正是能够靶向ABI5使其降解的CUL4-DDB1 E3连接酶的底物受体。同时，COP1能够在体外直接泛素化ABD1，在黑暗中负调节ABD1蛋白丰度，但在光照下不行。因此，COP1响应于ABA，通过使得ABD1蛋白不稳定，促进ABI5蛋白在黑暗中的翻译后稳定性。有趣的是，作者发现ABA在黑暗中诱导COP1在核中的积累，从而增强其传播ABA信号的活性。

结果3：Interestingly, we reveal that ABA induces the nuclear accumulation of COP1 in darkness, thus enhancing its activity in propagating the ABA signal. 

有趣的是，作者发现ABA在黑暗中诱导COP1在核中的积累，从而增强其传播ABA信号的活性。

结论：Together, our study uncovers that COP1 modulates ABA signaling during seedling growth in darkness by mediating ABA-induced ABI5 accumulation, demonstrating that plants adjust their ABA signaling mechanisms according to their light environment.

综上，本文的研究揭示了COP1在黑暗中通过介导ABA诱导的ABI5积累来调节幼苗生长期间的ABA信号，表明植物根据周边的光环境来调节自身的ABA信号转导机制。

** 李继刚 **

doi: https://doi.org/10.1093/plcell/koac073

Journal: The Plant Cell

Published date: February 28, 2022