Abstract
Endoplasmic reticulum (ER)-phagy is an important ER quality-control pathway that selectively removes misfolded or unfolded proteins and damaged ER membranes through autophagic degradation in the vacuole. Recent studies have identified small guanosine triphosphatases (GTPases) as important regulators of the autophagy pathway. However, how they couple stress signals to ER-phagy remains poorly understood in plants. Our recent work demonstrated that RABC1 regulates ER-phagy under dithiothreitol (DTT)-, tunicamycin (TM)-, and heat-induced ER stress through interaction with the exocyst complex component SEC5A. Upon ER stress, green fluorescent protein (GFP)-RABC1 was recruited to the ATG8e-positive autophagosomes from the ER and Golgi in root cells, whereas autophagic flux and calnexin 1 (CNX1)-mRFP-tagged ER membranes turnover were impaired in the rabc1 mutant. Together, our findings support a model in which RABC1 acts as a molecular switch that interacts with distinct effectors to regulate autophagy under different stress conditions.Abbreviations: RAB, ras-related in brain; ER, endoplasmic reticulum; GTPases, guanosine triphosphatases; GFP, green fluorescent protein; CNX1, calnexin 1; GDP, guanosine diphosphate; GTP, guanosine triphosphate; SAR1D, secretion associated ras related GTPase 1D; COPII, coat protein complex II; LDs, lipid droplets; DTT, dithiothreitol; TM, tunicamycin; TOR, target of rapamycin; ATG, autophagy-related; Rho, ras homology.