A dual phospholipase system instructs membrane hydrolysis during the final stages of plant autophagy

Abstract

Abstract Autophagy is a conserved intracellular catabolic process, critical for plant stress tolerance. Upon their delivery in the vacuole, how autophagic bodies containing cargo are hydrolyzed to warrant autophagy degradation remains unclear in multicellular organisms. Here, we found that two Arabidopsis phospholipases, LCAT4 and LCAT3, traffic to the vacuolar lumen and converge on autophagic bodies through fundamentally different routes. While LCAT4 directly binds ATG8 and uses autophagy as a transport system to reach the vacuole prepackaged within autophagosomes, LCAT3 traffics to the lytic compartment independently of autophagosome formation. Knocking out both genes causes an accumulation of autophagic bodies accompanied with a reduction in autophagy degradation. In vivo reconstitution demonstrated that LCAT3 can hydrolyse the membrane of autophagic bodies, enabling the activity of LCAT4 to enhance this process. Together, this work sheds light on the vacuolar stages of autophagy, showing that plants have evolved a multi-component pathway for the efficient disruption of autophagosomal membranes as a critical step for the completion of the autophagy pathway.