一种被选择性自噬降解的植物免疫受体。

A Plant Immune Receptor Degraded by Selective Autophagy.

机构信息

Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0722, USA; Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA.

Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA; Department of Biochemistry, University of Nebraska, Lincoln, NE 68588-0664, USA.

出版信息

Mol Plant. 2019 Jan 7;12(1):113-123. doi: 10.1016/j.molp.2018.11.011. Epub 2018 Nov 30.

DOI:10.1016/j.molp.2018.11.011

PMID:30508598

Abstract

Plants recycle non-activated immune receptors to maintain a functional immune system. The Arabidopsis immune receptor kinase FLAGELLIN-SENSING 2 (FLS2) recognizes bacterial flagellin. However, the molecular mechanisms by which non-activated FLS2 and other non-activated plant PRRs are recycled remain not well understood. Here, we provide evidence showing that Arabidopsis orosomucoid (ORM) proteins, which have been known to be negative regulators of sphingolipid biosynthesis, act as selective autophagy receptors to mediate the degradation of FLS2. Arabidopsis plants overexpressing ORM1 or ORM2 have undetectable or greatly diminished FLS2 accumulation, nearly lack FLS2 signaling, and are more susceptible to the bacterial pathogen Pseudomonas syringae. On the other hand, ORM1/2 RNAi plants and orm1 or orm2 mutants generated by the CRISPR/Cas9-mediated gene editing have increased FLS2 accumulation and enhanced FLS2 signaling, and are more resistant to P. syringae. ORM proteins interact with FLS2 and the autophagy-related protein ATG8. Interestingly, overexpression of ORM1 or ORM2 in autophagy-defective mutants showed FLS2 abundance that is comparable to that in wild-type plants. Moreover, FLS2 levels were not decreased in Arabidopsis plants overexpressing ORM1/2 derivatives that do not interact with ATG8. Taken together, these results suggest that selective autophagy functions in maintaining the homeostasis of a plant immune receptor and that beyond sphingolipid metabolic regulation ORM proteins can also act as selective autophagy receptors.

摘要

植物会回收非激活免疫受体，以维持其功能性免疫系统。拟南芥免疫受体激酶 FLAGELLIN-SENSING 2（FLS2）识别细菌鞭毛蛋白。然而，非激活的 FLS2 和其他非激活植物 PRR 被回收的分子机制尚不清楚。在这里，我们提供的证据表明，拟南芥粘蛋白（ORM）蛋白作为一种选择性自噬受体，介导 FLS2 的降解，而 ORM 蛋白先前被认为是神经酰胺生物合成的负调控因子。过表达 ORM1 或 ORM2 的拟南芥植株中，FLS2 积累检测不到或大大减少，几乎缺乏 FLS2 信号，并且对细菌病原体丁香假单胞菌更敏感。另一方面，ORM1/2 RNAi 植株和通过 CRISPR/Cas9 介导的基因编辑产生的 orm1 或 orm2 突变体中，FLS2 积累增加，FLS2 信号增强，对 P. syringae 的抗性增强。ORM 蛋白与 FLS2 和自噬相关蛋白 ATG8 相互作用。有趣的是，在自噬缺陷突变体中过表达 ORM1 或 ORM2 显示出与野生型植物相当的 FLS2 丰度。此外，在不与 ATG8 相互作用的 ORM1/2 衍生物过表达的拟南芥植物中，FLS2 水平没有降低。综上所述，这些结果表明，选择性自噬在维持植物免疫受体的内稳态方面起作用，并且除了神经酰胺代谢调节外，ORM 蛋白还可以作为选择性自噬受体发挥作用。