Nature, functions and trafficking of membrane lipids to support autophagosome formation in plant cells

Throughout development and in response to fluctuating environmental conditions, plants rely on autophagy to degrade and recycle cytoplasmic material thereby maintaining cellular homeostasis. This pathway is characterized by the de novo formation of double-membrane vesicles, the autophagosomes, that selectively sequester and deliver cargo to the vacuole for degradation. The biogenesis of these specialized structures is driven by intense membrane remodelling events of which both lipid quantity and quality are emerging key actors. Recent advances have unraveled the singular lipid composition of autophagic membranes, provided mechanistic insights into the functions of membrane lipids during autophagy and highlighted critical determinants of lipid transport for membrane expansion during autophagosome formation. In this review, we synthesize current knowledge on the nature, functions and trafficking of membrane lipids during autophagy with a particular focus on the model plant Arabidopsis thaliana. We further discuss outstanding questions regarding lipids dynamics and lipid-protein cooperation in autophagic membranes and compare lipid-related mechanisms in plants to that of other organisms. Together, these advances expand the conceptual framework of autophagy and underscore lipids as key regulators of plant acclimation and survival.