小柯机器人

美国霍华德·休斯医学研究所John D. MacMicking课题组发现，一种相分离的核内GBPL回路控制植物免疫力。相关论文于2021年5月26日在线发表在《自然》杂志上。

研究人员鉴定了植物鸟苷酸结合蛋白（GBP）样GTPases（GBPLs）的超家族，其在细胞核内组装为液-液相分离（LLPS）驱动的缩合物从而防止感染和自身免疫。在拟南芥中，该家族的两个成员（GBPL1和GBPL3）经历相变行为来控制转录反应，这是由于暴露于生物胁迫而触发的变构转换的一部分。

GBPL1，一种伪 GTP 酶，在基础条件下隔离具有催化活性的GBPL3，但当它根据免疫线索进入细胞核时被GBPL3 LLPS取代，进而驱动形成独特的无膜细胞器，称为 GBPL 防御激活凝聚物（GDAC）。在这些中尺度GDAC结构中，天然GBPL3直接结合防御基因启动子，并招募中介体复合物和RNA聚合酶II机器的特定转录共激活因子，从而大规模重新编程宿主基因表达来实现抗病性。

总之，这项研究确定了一个GBPL回路，它加强了相分离冷凝物的生物学重要性，并且在这种情况下，它是植物防御中不可或缺的参与者。

据悉，LLPS已成为了解无膜细胞器如何区分真核生物中不同细胞活动的核心范式。

附：英文原文

Title: A phase-separated nuclear GBPL circuit controls immunity in plants

Author: Shuai Huang, Shiwei Zhu, Pradeep Kumar, John D. MacMicking

Issue&Volume: 2021-05-26

Abstract: Liquid–liquid phase separation (LLPS) has emerged as a central paradigm for understanding how membraneless organelles compartmentalize diverse cellular activities in eukaryotes1,2,3. Here we identify a superfamily of plant guanylate-binding protein (GBP)-like GTPases (GBPLs) that assemble LLPS-driven condensates within the nucleus to protect against infection and autoimmunity. In Arabidopsis thaliana, two members of this family—GBPL1 and GBPL3—undergo phase-transition behaviour to control transcriptional responses as part of an allosteric switch that is triggered by exposure to biotic stress. GBPL1, a pseudo-GTPase, sequesters catalytically active GBPL3 under basal conditions but is displaced by GBPL3 LLPS when it enters the nucleus following immune cues to drive the formation of unique membraneless organelles termed GBPL defence-activated condensates (GDACs) that we visualized by in situ cryo-electron tomography. Within these mesoscale GDAC structures, native GBPL3 directly bound defence-gene promoters and recruited specific transcriptional coactivators of the Mediator complex and RNA polymerase II machinery to massively reprogram host gene expression for disease resistance. Together, our study identifies a GBPL circuit that reinforces the biological importance of phase-separated condensates, in this case, as indispensable players in plant defence.

DOI: 10.1038/s41586-021-03572-6

Source: https://www.nature.com/articles/s41586-021-03572-6

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
官方网址：http://www.nature.com/
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