Manipulation of the central autophagy component ZmATG8c affects thermotolerance in maize

Abstract Rising global temperatures present a substantial threat to crop production. Autophagy is an important catabolic process that promotes plant survival under stress, and AuTophaGy-related 8 (ATG8) proteins play key roles in plant autophagy, although the contributions of specific ATG8 isoforms to heat tolerance remain to be clarified. Here, we demonstrate that heat-induced expression of ZmATG8c promotes maize (Zea mays L.) thermotolerance during both vegetative and reproductive growth stages. ZmATG8c-knockout mutants showed lower seedling survival and grain yield under heat stress, whereas plants overexpressing ZmATG8c exhibited enhanced seedling survival and improved yield, which were attributable to greater autophagosome production, elevated levels of ATG8, and reduced accumulation of ubiquitinated protein aggregates. We also found that the heat-induced bZIP transcription factor ZmGBF1 could bind directly to the promoter of ZmATG8c and facilitate its expression. Maize gbf1 mutants showed significant inhibition of ZmATG8c thermal induction and increased sensitivity to heat stress. Our findings demonstrate that ZmATG8c and ZmGBF1 have a role in mediating thermotolerance, providing promising targets for engineering maize with improved resilience to thermal stress.