The ATG12-conjugating enzyme ATG10 is essential for autophagic vesicle formation in Arabidopsis thaliana

Autophagy is an important intracellular recycling system in eukalyotes that utilizes small vesicles to traffic cytosolic proteins and organelles to the vacuole for breakdown. Vesicle formation requires the conjugation of the two ubiquitin-fold polypeptides AFG8 and ATG 12 to phosphatidylethanolamine and the ATG5 protein, respectively. Using Arabidopsis thaliana mutants affecting the ATG5 target or the ATG7E1 required to initiate ligation of both ATG8 and ATG 12, we previously showed that the ATG8/12 conjugation pathways together are important where plants encounter nutrient stress and during senescence. To characterize the ATG12 conjugation pathway specifically, we characterized a null mutant eliminating the E2-conjugating enzyme ATG10 that, similar to plants missing ATG5 or ATG7, cannot form the ATG12-ATG5 conjugate. atg10-1 plants are hypersensitive to nitrogen and carbon starvation and initiate senescence and programmed cell death (PCD) more quickly than wild type, as indicated by elevated levels of senescence- and PCD-related miRNAs and proteins during carbon starvation. As detected with a GFP-ATG8a reporter; atg10-1 and alg5-1 mutant plants fail to accumulate autophagic bodies inside the vacuole. These results indicate that. ATG10 is essential for ATG72 conjugation and that the ATG12-ATG5 conjugate is necessary to form autophagic vesicles and For the timely progression of senescence and PCD in plants.