Abstract
Heat stress (HT) exerts significant negative impacts on plant growth, development, and productivity. In this study, we identified OsLAC12, a heat-induced laccase-encoding gene, as a key regulator of heat tolerance in rice. Functional validation confirmed that OsLAC12 encodes an active laccase, with supporting evidence showing that roots of OsLAC12 overexpression lines exhibited ~1.5-fold higher laccase activity and nearly three times the lignin content compared to the wild type (WT). Under HT, oslac12 mutants showed significantly lower seedling survival rates (~13-22%) than WT (~43%), whereas OE lines displayed higher survival rates (~68-74%). At the heading stage, OsLAC12 overexpression lines activated the antioxidant enzyme system in spikelets, regulated reactive oxygen species (ROS) levels in anthers, and mitigated HT-induced damage to pollen viability. In contrast, oslac12 mutants showed an average 10.8% reduction in pollen viability compared to WT, accompanied by significantly lower seed-setting rates. Collectively, our findings demonstrate that the laccase OsLAC12 positively regulates rice resistance to HT stress, providing critical insights for improving plant thermotolerance through genetic improvement of cell wall-associated pathways.