UVR8作用机制～激活：UV-B absorption by homodimeric UVR8 induces its monomerization and interaction with the E3 ubiquitin ligase COP1, leading ultimately to gene expression changes.

UVR8作用机制～失活：UVR8 is inactivated through redimerization, facilitated by RUP1 and RUP2.

主要发现：Here, we describe a semidominant, hyperactive allele, namely uvr8-17D, that harbors a glycine-101 to serine mutation. 

结果1-过表达表型：UVR8G101S overexpression led to weak constitutive photomorphogenesis and extreme UV-B responsiveness. UVR8G101S was observed to be predominantly monomeric in vivo and, once activated by UV-B, was not efficiently inactivated.

结果2-晶体结构：Analysis of a UVR8 crystal structure containing the G101S mutation revealed the distortion of a loop region normally involved in stabilization of the UVR8 homodimer.

结果3-UVR8变体：Plants expressing a UVR8 variant combining G101S with the previously described W285A mutation exhibited robust constitutive photomorphogenesis.

结论：This work provides further insight into UVR8 activation and inactivation mechanisms and describes a genetic tool for the manipulation of photomorphogenic responses.

植物的紫外线-B（UV-B）光受体UVR8在UV-B适应和存活中扮演着非常重要的作用。UVR8同型二聚体对于UV-B的吸收诱导其单体化，从而与E3泛素连接酶COP1互作，最终导致基因表达的改变。UVR8在RUP1和RUP2的促进下会进行重聚合，进入失活状态。本文中，作者报道了一个半显性、超活跃的等位基因，即uvr8-17D，一个含有甘氨酸-101到丝氨酸的突变。UVR8G101S过表达会导致组成型光形态发生减弱，而UV-B响应变得极端。在体内观察到的UVR8G101主要是单体，而且一旦被UV-B激活，就不能有效地失活。对于含有G101S的UVR8蛋白晶体结构分析显示，通常参与稳定UVR8同型二聚体的环区发生畸变。在植物中，表达G101S和先前报道的W285A突变的UVR8变体，表现出强大的组成型光形态发生。本文的研究结果为UVR8的激活和失活机制提供了新的视野，同时揭示了一个调控光形态响应的遗传工具。