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 <i>OsLAC12</i>, a heat-induced laccase-encoding gene, as a key regulator of heat tolerance in rice. Functional validation confirmed that <i>OsLAC12</i> encodes an active laccase, with supporting evidence showing that roots of <i>OsLAC12</i> overexpression lines exhibited ~1.5-fold higher laccase activity and nearly three times the lignin content compared to the wild type (WT). Under HT, <i>oslac12</i> 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, <i>OsLAC12</i> 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, <i>oslac12</i> 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 <i>OsLAC12</i> positively regulates rice resistance to HT stress, providing critical insights for improving plant thermotolerance through genetic improvement of cell wall-associated pathways.