Disease-stage-associated transcriptional responses underlying bacterial wilt resistance in tobacco cultivar Yunyan 87 caused by Ralstonia solanacearum.

Bacterial wilt caused by Ralstonia solanacearum severely limits tobacco production, yet the molecular basis of resistance to vascular wilt diseases remains poorly understood. We integrated field phenotyping, pathogen isolation, and transcriptomic analyses across different disease stages to investigate root responses of the resistant tobacco cultivar Yunyan 87 at healthy, moderately infected, and severely infected stages. Disease progression was accompanied by marked root biomass loss, with fresh and dry weights reduced by approximately 60% and 70%, respectively. Transcriptomic analyses identified 994 up-regulated and 1,151 down-regulated genes at the moderate stage, and 2,158 up-regulated and 2,284 down-regulated genes at the severe stage. WGCNA identified a disease severity-associated regulatory module. Functional enrichment analyses showed that moderate infection activated stress perception and redox homeostasis, whereas severe infection strongly suppressed translation and ribosome biogenesis. Dynamic expression pattern analysis further revealed coordinated activation of phenylpropanoid metabolism and lignin biosynthesis, and synergistic induction of MAPK, salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) signaling pathways, followed by progressive metabolic repression. Key transcription factor families, including WRKY, MYC2, and ERF, exhibited distinct stage-dependent expression patterns. Collectively, our results demonstrate a disease-stage-associated transcriptional reprogramming strategy that balances defense activation and metabolic restraint during bacterial wilt progression, providing valuable regulatory networks and candidate genes for breeding tobacco cultivars with enhanced resistance.