Regulation of plant autophagy by YWHA/14-3-3 proteins

ATG1/ATG13, a core kinase complex regulator in the macroautophagy/autophagy machinery during autophagosome formation, is modulated in a sophisticated manner by posttranslational ubiquitination to determine proper autophagy levels in eukaryotic cells. However, the mechanisms that regulate the stability and activity of this complex remain elusive. We recently identified two negative regulators of autophagy, 14-3-3λ and 14-3-3k, that help redundantly regulate autophagy by directly associating with SINAT and ATG13s. The specific interaction between the molecular adaptors 14-3-3λ and 14-3-3κ and phosphorylated ATG13a is crucial for SINAT-mediated ubiquitination and degradation of ATG13a, and for maintenance of the ATG1-ATG13 complex. Consistent with the function of 14-3-3s in autophagy, the 14-3-3λ 14-3-3κ double mutant exhibits enhanced tolerance to nutrient deprivation with constitutive induction of autophagy. These findings demonstrate that 14-3-3λ and 14-3-3k coordinate with SINATs to regulate both the homeostasis of ATG13 phosphorylation and the induction of autophagy in plants.