N-degron-mediated ATG8 isoform switching controls plant thermotolerance

Macroautophagy/autophagy is a highly conserved catabolic pathway in eukaryotes that mediates the selective degradation and recycling of cellular components through the formation of double-membrane autophagosomes. ATG8 is a core component of autophagy and determines cargo selectivity through interactions with specific cargo receptors. Higher plants harbor multiple ATG8 isoforms, implying potential functional diversification; however, the biological significance of this isoform expansion remains largely unexplored. In a recent study, we identified UBR7 (UBIQUITIN PROTEIN LIGASE E3 COMPONENT N-RECOGNIN 7) as a novel N-recognin that targets ATG8a for proteasomal degradation via the Arg/N-degron pathway. This selective degradation triggers isoform switching by enabling the replacement of ATG8a with alternative ATG8 isoforms. Notably, this process occurs specifically during the recovery phase following heat stress and plays a critical role in enhancing thermotolerance. Our findings provide new insights into the functional specialization and dynamic regulation of ATG8 isoforms in plants and suggest new directions for improving crop resilience under climate-associated temperature fluctuations.<b>Abberivations</b> HS, heat stress: HSP, heat shock protein; RBP, RNA-binding protein; UTR, untranslated region.