The CsmiR397a - CsLAC17 module regulates lignin biosynthesis to balance the tenderness and gray blight resistance in young tea shoots

Lignin accumulation can enhance the disease resistance of young tea shoots ( ). It also greatly reduces their tenderness, which indirectly affects the quality and yield of tea. Therefore, the regulation of lignin biosynthesis appears to be an effective way to balance tenderness and disease resistance in young tea shoots. In this study, we identified a laccase gene, , that is induced during tenderness reduction and gray blight infection in young tea shoots. Overexpression of significantly increased the lignin content in transgenic , enhancing their resistance to gray blight and decreasing stem tenderness. In addition, we found that was negatively regulated by the upstream by 5'-RLM-RACE, dual-luciferase assay, and transient expression in young tea shoots. Interestingly, the expression of was inhibited during tenderness reduction and gray blight infection of young tea shoots. Overexpression of reduced lignin accumulation, resulting in decreased resistance to gray blight and increased stem tenderness in transgenic . Furthermore, the transient overexpression of and in tea leaves directly confirms the function of the - module in lignin biosynthesis and its effect on disease resistance. These results suggest that the module is involved in balancing tenderness and gray blight resistance in young tea shoots by regulating lignin biosynthesis.