Persulfidation of ATG18a regulates autophagy under ER stress inArabidopsis

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Abstract
Hydrogen sulfide (H2S) is an endogenously generated gaseous signaling molecule, which recently has been implicated in autophagy regulation in both plants and mammals through persulfidation of specific targets. Persulfidation has been suggested as the molecular mechanism through which sulfide regulates autophagy in plant cells. ATG18a is a core autophagy component that is required for bulk autophagy and also for reticulophagy during endoplasmic reticulum (ER) stress. In this research, we revealed the role of sulfide in plant ER stress responses as a negative regulator of autophagy. We demonstrate that sulfide regulates ATG18a phospholipid-binding activity by reversible persulfidation at Cys103, and that this modification activates ATG18a binding capacity to specific phospholipids in a reversible manner. Our findings strongly suggest that persulfidation of ATG18a at C103 regulates autophagy under ER stress, and that the impairment of persulfidation affects both the number and size of autophagosomes. Significance Endoplasmic reticulum (ER) stress is a condition triggered by adverse environmental conditions, which in plants include extreme heat, pathogen infection, and drought. These stresses can have a devastating effect on agricultural productivity, and the appropriate responses of plants to stress are therefore critical. Autophagy is a macromolecular degradation pathway that is activated in response to stress, including ER stress, but the mechanism by which it is regulated is still unclear. Here, we describe a modification, persulfidation, of the key autophagy protein ATG18a that affects its binding to membranes and controls its activity. This tight regulation of autophagy therefore allows plants to control the tradeoff between growth and stress tolerance.

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