Plant UV‐B responses are mediated by the photoreceptor UV RESISTANCE LOCUS 8 (UVR8). In response to UV‐B irradiation, UVR8 homodimers dissociate into monomers that bind to the E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1). The interaction of the C27 domain in the C‐terminal tail of UVR8 with the WD40 domain of COP1 is critical for UV‐B signaling. However, the function of the last 17 amino acids (C17) of the C‐terminus of UVR8, which are adjacent to C27, is unknown, although they are largely conserved in land plants. In this study, we established that Arabidopsis thaliana UVR8 C17 binds to full‐length UVR8, but not to COP1, and reduces COP1 binding to the remaining portion of UVR8, including C27. We hypothesized that overexpression of C17 in a wild‐type background would have a dominant negative effect on UVR8 activity; however, C17 overexpression caused strong silencing of endogenous UVR8, precluding a detailed analysis. We therefore generated YFP‐UVR8^N423 transgenic lines, in which C17 was deleted, to examine C17 function indirectly. YFP‐UVR8^N423 was more active than YFP‐UVR8, suggesting that C17 inhibits UV‐B signaling by attenuating binding between C27 and COP1. Our study reveals an inhibitory role for UVR8 C17 in fine‐tuning UVR8–COP1 interactions during UV‐B signaling.

中文翻译：

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感光器UVR8的C端17个氨基酸参与了UV-B信号传导的微调。

植物的UV-B反应是由光感受器抗紫外线部位8（UVR8）介导的。响应UV-B辐射，UVR8同型二聚体解离成与E3泛素连接酶组成的单体构成的光生化单体（COP1）。UVR8 C末端尾部的C27结构域与COP1 WD40域的相互作用对于UV-B信号传导至关重要。但是，UVR8 C末端的最后17个氨基酸（C17）的功能与C27相邻，但尚不知道，尽管它们在陆地植物中基本上是保守的。在这项研究中，我们确定拟南芥UVR8 C17与全长UVR8绑定，但与COP1不绑定，并降低COP1与UVR8其余部分（包括C27）的绑定。我们假设在野生型背景中C17的过表达将对UVR8活性起显性负作用。但是，C17过表达导致内源UVR8强烈沉默，因此无法进行详细分析。因此，我们产生了YFP-UVR8 ^N423转基因株系，其中的C17被删除，以间接检查C17的功能。YFP-UVR8 ^N423比YFP-UVR8活性更高，表明C17通过减弱C27和COP1之间的结合来抑制UV-B信号传导。我们的研究显示，在微调UV-B信号传导期间，UVR8 C17在微调UVR8-COP1相互作用中具有抑制作用。