Abstract:

Objective: This study aims to investigate the change pattern of transcriptomics of Camellia olefolia root in the early stage of its interaction with endophytic bacteria, so as to provide reference for clarifying the molecular mechanism of interaction between C. olefolia and endophytic bacteria. Method: An interaction system between endophytic Bacillus subtilis 1-L-29 and C. olefolia root was constructed. The transcriptomes of the interaction system were sequenced and analyzed by RNA-Seq at different time periods (0, 6, 12, 24 h). Result: 1) The transcriptome sequencing produced a total of 52 958 922 sequences, about 46.1 Gb, and 10 314 differentially expressed genes (FDR < 0.05 and |log₂FC|>1). With the extension of interaction time, the expression of differentially expressed genes showed a high-low-high trend. The number of differentially expressed genes at 6 h after vaccination was 6 306, of which 3 434 genes were significantly up-regulated and 2 572 were significantly down-regulated. At 24 h, a total of 903 genes were significantly up-regulated, and 526 genes were significantly down-regulated. At 24 h, a total of 1 195 genes were significantly up-regulated, and 1 384 genes were significantly down-regulated. 2) Go enrichment analysis showed that the biological process and molecular function of C. olefolia were changed most obviously after 6 hours of interaction. In the biological process, phosphate metabolism pathway, phosphorus-containing compound metabolism pathway, hormone response pathway, jasmonic acid metabolism pathway, bacterial response pathway, hormone-mediated signal pathway, cell response to hormone stimulation, phenylpropane biosynthesis pathway and so on were enriched. The activities of terpene synthase and dioxygenase in molecular functions were enriched. The membrane and intrinsic components of the membrane were enriched. 3) KEGG pathway analysis showed that the differentially expressed genes were mainly enriched into carbohydrate metabolism, amino acid metabolism, signal transduction, environmental adaptability and other pathways. The metabolic pathways enriched at 6 h after inoculation were significantly different from those at 12 h and 24 h, among which the significant differences were mainly plant hormone synthesis signaling pathway, plant pathogen interaction pathway and phenylpropanol biosynthesis pathway. 4) The genes with large changes in expression included auxin-inducible protein coding gene (SAUR), xyloglucan endoglycosyltransferase/hydrolytic protease coding gene (XTH), jasmonate ZIM domain protein coding gene (TIFY), calmodulin coding gene (CAM2), transcription factor MYB coding gene, disease resistance protein coding gene (RPM, RPS), respiratory burst oxidase coding gene (RBOHC), peroxidase coding gene (POD). Conclusion: In this study, for the first time, the living body interaction system has been used to analyze the endophytic bacteria-C. olefolia root interaction transcriptome at different time periods. The results indicate that endophytic bacteria can stimulate plant root growth, increase resistance, and induce immune response, but then the immune response gradually weakens. The results of this study laid a theoretical foundation for the analysis of the molecular mechanism of interaction between endophytic bacteria and C. oleifera.

Key words: Camellia oleifera, endophytic bacteria, Bacillus subtilis, transcriptome analysis, early interactions