Transcriptome Analysis and Genome-Wide Gene Family Identification Enhance Insights into Bacterial Wilt Resistance in Tobacco

Bacterial wilt, caused by the Ralstonia solanacearum species complex, is one of the most damaging bacterial diseases in tobacco and other Solanaceae crops. In this study, we conducted an analysis and comparison of transcriptome landscape changes in seedling roots of three tobacco BC4F5 lines, C244, C010, and C035, with different resistance to bacterial wilt at 3, 9, 24, and 48 h after R. solanacearum infection. A number of biological processes were highlighted for their differential enrichment between C244, C010, and C035, especially those associated with cell wall development, protein quality control, and stress response. Hence, we performed a genome-wide identification of seven cell wall development-related gene families and six heat shock protein (Hsp) families and proposed that genes induced by R. solanacearum and showing distinct expression patterns in C244, C010, and C035 could serve as a potential gene resource for enhancing bacterial wilt resistance. Additionally, a comparative transcriptome analysis of R. solanacearum-inoculated root samples from C244 and C035, as well as C010 and C035, resulted in the identification of a further 33 candidate genes, of which Nitab4.5_0007488g0040, a member of the pathogenesis-related protein 1 (PR-1) family, was found to positively regulate bacterial wilt resistance, supported by real-time quantitative PCR (qRT-PCR) and virus-induced gene silencing (VIGS) assays. Our results contribute to a better understanding of molecular mechanisms underlying bacterial wilt resistance and provide novel alternative genes for resistance improvement

Comprehensive genome sequence analysis of Ralstonia solanacearum gd-2, a phylotype I sequevar 15 strain collected from a tobacco bacterial phytopathogen

IntroductionPlant bacterial wilt is an important worldwide disease caused by Ralstonia solanacearum which is a complex of species.MethodsIn this study, we identified and sequenced the genome of R. solanacearum strain gd-2 isolated from tobacco.ResultsStrain gd-2 was identified as R. solanacearum species complex (RSSC) phylotype I sequevar 15 and exhibited strong pathogenicity to tobacco. The genome size of gd-2 was 5.93 Mb, including the chromosomes (3.83 Mb) and the megaplasmid (2.10 Mb). Gene prediction results showed that 3,434 and 1,640 genes were identified in the chromosomes and plasmids, respectively. Comparative genomic analysis showed that gd-2 exhibited high conservation with ten highly similar strain genomes and the differences between gd-2 and other genomes were mainly located at positions GI12-GI14. 72 type III effectors (T3Es) were identified and RipAZ2 was a T3E specific to gd-2 compared with other eight sequenced strain.DiscussionOur study provides a new basis and evidence for studying the pathogenic mechanism of R. solanacearum