StCCR6-Mediated Lignin Biosynthesis Enhances Potato Resistance Against Ralstonia solanacearum

Abstract Background Bacterial wilt, caused by Ralstonia solanacearum, is one of the most destructive soil-borne diseases worldwide and severely threatens global potato (Solanum tuberosum) production. Lignin deposition in the cell wall constitutes a critical physical barrier for plant defense; however, the regulatory mechanisms governing lignin-mediated resistance in potato remain incompletely understood. Results Based on previously published temporal transcriptome and metabolome datasets of potato tubers treated with a low dose of deoxynivalenol (DON) across four time points (0, 4, 12, and 48 h), we dissected the defense response. Multi-omics screening revealed that the phenylpropanoid biosynthetic pathway (ko00940) was significantly enriched at 12 h, and StCCR6 (CCR2), a cinnamoyl-CoA reductase gene, was identified as the most strongly DON-responsive node. Metabolomic profiling further showed that DON treatment drove the accumulation of the lignin monomers coniferyl alcohol and sinapyl alcohol. Functional validation using transgenic lines demonstrated that StCCR6 overexpression thickened cell walls via accelerated lignin deposition and elevated the activities of ROS-scavenging enzymes (SOD, POD, and CAT), thereby enhancing resistance to R. solanacearum in a detached-leaf assay. Conversely, StCCR6 knockout lines exhibited reduced lignin content, elevated reactive oxygen species and oxidative damage, and increased pathogen susceptibility. Conclusion These results establish StCCR6 as an essential regulator that couples lignin-based physical defense with enzymatic antioxidant scavenging under low-dose DON induction, providing a valuable genetic target for engineering broad-spectrum disease resistance in crops.