Overexpression of OsCCR1, OsCOMT5, OsCAD2 and OsCCoAOMT1 Genes Enhances Lignin Accumulation and Confers Tolerance Against Rhizoctonia solani in Rice (Oryza sativa).

The necrotrophic fungus, Rhizoctonia solani is the major cause of sheath blight, a disease that leads to a significant reduction in rice yield, posing a serious threat to food security. Traditional breeding approaches have struggled to develop effective resistance, highlighting the importance of transgenic technology as a promising solution. This study explored the relationship between enhanced lignin production and the overexpressing key lignin biosynthesis genes (OsCCR1, OsCOMT5, OsCAD2, and OsCCoAOMT1), demonstrating that increased lignin accumulation strengthens defense mechanisms against R. solani by preventing its penetration of the cell wall. Thioacidolysis analysis revealed higher lignin levels in the leaf sheath tissues of OX-OsCCR1 transgenic rice plants, which effectively blocked fungal hyphae invasion, as confirmed by confocal and scanning electron microscopy. Similarly, the cell walls of OX-OsCOMT5 transgenic lines accumulated significantly higher levels of cell wall-bound phenolics, which inhibited R. solani ingress and infection peg formation. Notably, OX-4C transgenic rice plants, overexpressing all four lignin biosynthesis genes, exhibited elevated levels of lignin in the leaf sheath during early infection, serving as a robust first line of defense. These findings underscore the critical role of cell wall restructuring, particularly through increased lignin deposition, in combating sheath blight infection and enhancing crop resilience. Engineering the lignin biosynthesis pathway provides a promising approach for developing broad-spectrum resistance to fungal pathogens in other economically important crops, paving the way for sustainable agriculture and food security.