Conjugation of ATG8 to vacuolar membranes as a response to cell wall damage

ATG8 is a well-characterized protein involved in autophagy that binds to the double-membrane enclosed phagophore. In a new preprint, Julian et al. explore their finding that ATG8 binds to the single-membrane enclosed vacuolar membrane (tonoplast). They observed that this binding is enhanced by treatments that weaken the cell wall, such as inhibition of cellulose synthase. To identify its function, they generated plants defective in conjugation of ATG8 to single membranes (ΔCASM), which blocks this specific interaction but does not affect autophagy more broadly. ΔCASM plants show defects in tonoplast and vacuolar integrity and are more sensitive to cell-wall damage. The authors propose a vacuolar quality control (VQC) pathway in which cell wall damage triggers a change in turgor pressure and vacuolar pH which leads to ATG8 recruitment and membrane remodeling to prevent tonoplast lysis in conditions where cell wall integrity is damaged. This work has identified a new quality control pathway for vacuoles and links ATG8 with cell integrity sensing. (Summary by Mary Williams @PlantTeaching) bioRxiv  10.1101/2024.04.21.590262