Phosphatidylinositol-4-phosphate controls autophagosome formation in Arabidopsis thaliana
Résumé
Autophagy is an intracellular degradation mechanism critical for plant acclimation to environmental stresses. Central to autophagy is the formation of specialized vesicles, the autophagosomes (AP), which target and deliver cargo to the lytic vacuole. Autophagosome formation relies on intense membrane remodeling events, starting with the sequential recruitment of the autophagy actors ATG proteins, from the cytosol to the phagophore assembly site, a lipido-proteic core from which the initial autophagy structure, the phagophore, is assembled. The phagophore then expands by addition of lipids and proteins and finally closes to form a completed double membrane vesicle which traffics to the vacuole and fuses with the tonoplast. At this time, the molecular mechanism underlying autophagosome formation remains largely unknown in plants. In particular, while AP biogenesis is a membrane based process, very little is known about the functional contribution of lipids in plant autophagy. Upstream of the present study, we performed a lipid inhibitor screen to identify lipids that are critically engaged in autophagy in Arabidopsis; this unraveled the importance of Phosphatidylinositol-4-phosphate (PI4P) that we functionally characterized here.
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