Nuclear Localized O-fucosyltransferase SPY Facilitates PRR5 Proteolysis to Fine-tune the Pace of Arabidopsis Circadian Clock

First author: Yan Wang; Affiliations: CAS Institute of Botany (中科院植物所): Beijing, China

Corresponding author: Lei Wang

Post-translational modifications play essential roles in finely modulating eukaryotic circadian clock systems. In plants, the effects of O-glycosylation on the circadian clock and the underlying mechanisms remain largely unknown. O-fucosyltransferase SPINDLY (SPY), and O-GlcNAc transferase SECRET AGENT (SEC) are two prominent O-glycosylation enzymes in higher plants, with both overlapped and unique functions in plant growth and development. Unlike the critical role of O-GlcNAc in regulating animal circadian clock, here we demonstrated that nuclear localized SPY but not SEC, specifically modulates the pace of Arabidopsis circadian clock. By identifying the interactome of SPY, we characterized PSEUDO RESPONSE REGULATOR 5 (PRR5), one of core circadian clock components, as a new SPY-interacting protein. PRR5 can be O-fucosylated by SPY in planta, while point mutations in the SPY catalytic domain abolishes the O-fucosylation of PRR5. The protein abundance of PRR5 is strongly increased in spy mutants, while the degradation rate of PRR5 is much reduced, suggesting PRR5 proteolysis is promoted by SPY-mediated O-fucosylation. Moreover, multiple lines of genetic evidence indicate PRR5 is a major downstream target of SPY to specifically mediate its modulation on circadian clock. Collectively, our findings provide a novel insight into the specific role of O-fucosyltransferase activity of SPY in modulating the circadian clock, and implicate O-glycosylation might have an evolutionarily conserved role in modulating circadian clock system, via O-GlcNAcylation in mammals, but via O-fucosylation in higher plants.

翻译后修饰在精细调节真核生物钟系统中起重要作用。在植物中，O-糖基化对昼夜节律时钟的影响及潜在调控机制仍不清楚。 O-岩藻糖转移酶SPY和O-连N-乙酰氨基葡萄糖（O-GlcNAc）转移酶SEC是高等植物中两种重要的O-糖基化酶，这两个酶在植物生长和发育中具有重复的作用，同时也有各自特定的功能。与O-GlcNAc在动物生物钟中的关键作用不同，本文中作者的研究显示了核定位的SPY，而不是SEC可以特异性调节拟南芥生物钟的速度。通过鉴定SPY的相互作用组，作者发现一个生物钟核心时钟组分PRR5是一种新的SPY互作蛋白。 在植物体内，PRR5可以被SPY进行O-岩藻糖基化，而SPY催化域中的点突变则使得PRR5不能被O-岩藻糖基化。在spy突变体中，PRR5蛋白的丰度大大增加，而PRR5的降解大大降低，这表明SPY介导的O-岩藻糖基化促进了PRR5的蛋白水解。此外，多个株系的遗传学证据表明，PRR5是SPY的主要下游靶基因，以介导其在生物钟上的调控作用。总的来说，本文的研究为SPY的O-岩藻糖基转移酶活性在调节昼夜节律中的特定作用提供了新的见解，并且暗示O-糖基化可能在调节生物的昼夜节律系统中具有演化上保守的作用，在哺乳动物中通过O-GlcNAc糖基化修饰，而在高等植物中则通过O-岩藻糖基化。

通讯：王雷 (http://sourcedb.ib.cas.cn/cn/expert/201402/t20140217_4033081.html)

个人简介：1999年，东北师范大学，学士； 2002年，吉林农业大学，硕士； 2006年，中国科学院植物研究所，博士；2006-2013年，美国俄亥俄州立大学，博士后。

研究方向：植物生物钟分子系统。

doi: https://doi.org/10.1016/j.molp.2019.12.013

Journal: Molecular Plant

Published date: December 31, 2019