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The plant RABC1 GTPase coordinates with exocyst component SEC5A in regulating ER-phagy under endoplasmic reticulum
Shuai Hu1,2, Dongmei Zhu1,2, Xiaohui Ma1,2
1State Key Laboratory for Development and Utilization of Forest Food Resources, Zhejiang A&F University, Hangzhou 311300, China.
The Plant Cell
|July 6, 2026
Summary
The plant RAB GTPase RABC1 regulates endoplasmic reticulum (ER) degradation (ER-phagy) during ER stress. RABC1 coordinates with SEC5A to promote autophagosome formation, revealing a novel ER-phagy mechanism.
Area of Science:
- Plant cell biology
- Molecular plant science
- Autophagy research
Background:
- Small GTPases are key regulators of intracellular transport.
- The roles of small GTPases in endoplasmic reticulum (ER) stress and selective autophagy are not well understood.
- ER-phagy, the selective degradation of ER components via autophagy, is crucial for cellular homeostasis.
Purpose of the Study:
- To investigate the function of the plant RAB GTPase RABC1 in ER stress response and ER-phagy.
- To elucidate the molecular mechanism by which RABC1 regulates ER-phagy.
- To identify potential interacting partners of RABC1 in ER-phagy.
Main Methods:
- Characterization of rabc1 mutants under various stress conditions (heat shock, dithiothreitol, tunicamycin).
- Subcellular localization studies of RABC1 using fluorescent protein tagging.
- Analysis of autophagosome formation and cargo degradation (Calnexin-GFP) in wild-type and mutant backgrounds.
- Co-immunoprecipitation assays to identify RABC1 interacting partners.
- Genetic interaction studies using double mutants.
Main Results:
- rabc1 mutants exhibit hypersensitivity to ER stress.
- RABC1 localizes to the ER and Golgi and is recruited to autophagosomes during ER stress.
- Autophagic turnover of the ER chaperone Calnexin is impaired in rabc1 mutants.
- RABC1 interacts with the exocyst subunit SEC5A, and this interaction is essential for SEC5A recruitment to autophagosomes.
- RABC1 and SEC5A show an additive genetic interaction in ER stress sensitivity.
Conclusions:
- RABC1 is a novel regulator of ER-phagy in plants.
- RABC1, in coordination with SEC5A, promotes autophagosome formation during ER stress.
- This study reveals a new mechanism involving a plant RAB GTPase in the regulation of ER-phagy.
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