Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
Cell. 2010 Jun 25;141(7):1230-40. doi: 10.1016/j.cell.2010.05.007.
Light plays a profound role in plant development, yet how photoreceptor excitation directs phenotypic plasticity remains elusive. One of the earliest effects of light is the regulated translocation of the red/far-red photoreceptors, phytochromes, from the cytoplasm to subnuclear foci called phytochrome nuclear bodies. The function of these nuclear bodies is unknown. We report the identification of hemera, a seedling lethal mutant of Arabidopsis with altered phytochrome nuclear body patterns. hemera mutants are impaired in all phytochrome responses examined, including proteolysis of phytochrome A and phytochrome-interacting transcription factors. HEMERA was identified previously as pTAC12, a component of a plastid complex associated with transcription. Here, we show that HEMERA has a function in the nucleus, where it acts specifically in phytochrome signaling, is predicted to be structurally similar to the multiubiquitin-binding protein, RAD23, and can partially rescue yeast rad23mutants. Together, these results implicate phytochrome nuclear bodies as sites of proteolysis.
光在植物发育中起着深远的作用，但光受体的激发如何指导表型可塑性仍然难以捉摸。光的最早影响之一是调节红光/远红光光受体（光敏色素）从细胞质到称为光敏色素核体的亚核焦点的易位。这些核体的功能尚不清楚。我们报告了拟南芥hemera 突变体的鉴定，该突变体的光敏色素核体模式发生改变。hemera 突变体在所有检测到的光敏色素反应中都受到损害，包括光敏色素 A 和光敏色素相互作用转录因子的蛋白水解。HEMERA 先前被鉴定为 pTAC12，它是与转录相关的质体复合物的一个组成部分。在这里，我们表明 HEMERA 在核中有功能，在那里它专门作用于光敏色素信号转导，结构上预测与多泛素结合蛋白 RAD23 相似，并可以部分挽救酵母 rad23 突变体。这些结果共同表明光敏色素核体是蛋白水解的部位。
