Multi-omics profiling of defense enzymes and phenylpropanoid regulation in Camellia sinensis post-Colletotrichum camelliae inoculation

Tea anthracnose, caused by Colletotrichum camelliae , significantly impacts tea production. During the plant disease resistance process, the accumulation of reactive oxygen(ROS) species causes oxidative damage, while defensive enzymes enhance resistance by scavenging ROS. Modern omics technologies can systematically analyze the gene regulatory network and metabolic response mechanism of tea plants in response to pathogen infection. Leaves of Camellia sinensis from South China Agricultural University’s germplasm nursery were inoculated with C. camelliae, a pathogen isolated, purified, and confirmed via morphological/molecular identification. Sporulation conditions for this anthracnose pathogen were optimized, with a culture medium containing KH₂PO₄, NaH₂PO₄, and NaHCO₃ demonstrating enhanced sporulation capacity. Significant differences in defense enzyme activities-superoxide dismutase, peroxidase, and phenylalanine ammonia-lyase were observed between resistant cultivar 'Shuixian 7' and susceptible 'Lingtou Dancong' under anthracnose stress. While both materials exhibited similar response trends, 'Shuixian 7' displayed more intense and rapid changes. Metabolome sequencing at 1 and 5 days post-inoculation (dpi) in anthracnose revealed hundreds of differential metabolites in 'Shuixian 7' compared to 'Lingtou Dancong', with flavonoids constituting the predominant class. Specifically, quercetin-3-O-glucoside, quercetin, kaempferol-3-O-galactoside, and quercetin-3-O-sophoroside were significantly upregulated, whereas acacetin, luteolin, apigenin-7-O-neohesperidoside, and apigenin-6-C-glucoside were downregulated. In vitro antifungal assays confirmed that quercetin exhibited the strongest inhibitory effect on C. camelliae among eight tested metabolites at equivalent concentrations. RNA-Seq analysis of infection five infection time-points identified differential genes primarily enriched in metabolic pathways and plant-pathogen interactions. Analysis established a critical link between defense enzymes and reactive oxygen species during biotic stress. Seven Rboh genes were identified from the C. sinensis genome, with bioinformatic characterization revealing CsRbohC as highly expressed in transcriptomic data. Based on the experimental results with pathogen-resistant 'Shuixian 7' and susceptible 'Lingtou Dancong' tea materials inoculated with C. camelliae , significant differences were observed in defense enzyme activities and metabolomic profiles, where flavonoid metabolites were markedly enriched in 'Shuixian 7'; transcriptome analysis further revealed key enrichment in plant-pathogen interaction pathways. Additionally, bioinformatics screening of the CsRboh gene family highlighted CsRbohC as a highly expressed regulator during biotic stress.