OsLAC12, a Laccase-Encoding Gene, Contributes to Rice Heat Tolerance Through Regulation of Antioxidant Defense and Secondary Metabolism

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.