Plant Rho GTPase signaling promotes autophagy.

Youshun Lin, Yonglun Zeng, Ying Zhu, Jinbo Shen, Hao Ye, Liwen Jiang

Molecular plant 2021 Jun 07

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The roles of Rho family guanosine triphosphatases (GTPases) of plants (ROPs) in modulating plant growth and development have been well characterized. However, little is known about the roles of ROP signaling pathways in regulating plant autophagy and autophagosome formation. In this study, we identify a unique ROP signaling mechanism, which mediates developmental to autophagic transition under stress conditions in the model plant Arabidopsis. Loss-of-function mutants of ROP8 showed stress-induced hypersensitive phenotypes and compromised autophagic flux. Similar to other ROPs in the ROP/RAC family, ROP8 exhibits both plasma membrane and cytosolic punctate localization patterns. Upon autophagic induction, active ROP8 puncta colocalize with autophagosomal markers and are degraded inside the vacuole. In human cells, RalB, an RAS subfamily GTPase, engages its effector Exo84 for autophagosome assembly. However, a RalB counterpart is missing in the plant lineage. Intriguingly, we discovered that plant ROP8 promotes autophagy via its downstream effector Sec5. Live-cell super-resolution imaging showed that ROP8 and Sec5 reside on phagophores for autophagosome formation. Taken together, our findings highlight a previously unappreciated role of an ROP8-Sec5 signaling axis in autophagy promotion, providing new insights into how plants utilize versatile ROP signaling networks to coordinate developmental and autophagic responses depending on environmental changes. Copyright © 2021 The Author. Published by Elsevier Inc. All rights reserved.

Citation

Youshun Lin, Yonglun Zeng, Ying Zhu, Jinbo Shen, Hao Ye, Liwen Jiang. Plant Rho GTPase signaling promotes autophagy. Molecular plant. 2021 Jun 07;14(6):905-920