Abstract
Tobacco bacterial wilt (TBW) caused by Ralstonia solanacearum is the most serious soil-borne disease of tobacco. However, molecular mechanism information of R. solanacearum resistance is limited to tobacco, hindering better breeding of resistant tobacco. In this study, the expression profiles of the rootstalks of Yunyan87 (susceptible cultivar) and Fandi3 (resistant cultivar) at different stages after R. solanacearum infection were compared to explore molecular mechanisms of tobacco resistance against the bacterium. Findings from gene-expression profiling indicated that the number of upregulated differentially expressed genes (DEGs) at 3 and 7 days post-inoculation (dpi) increased significantly in the resistant cultivar. WRKY6 and WRKY11 family genes in WRKY transcription factors, ERF5 and ERF15 family genes in ERFs transcription factors, and genes encoding PR5 were significantly upregulated in the resistant cultivar response to the infection. For the first time, WRKY11 and ERF15 were found to be possibly involved in disease-resistance. The Kyoto Encyclopedia of Genes and Genomes analysis demonstrated glutathione metabolism and phenylpropane pathways as primary resistance pathways to R. solanacearum infection. In the resistant cultivar, DEGs encoding CYP450, TCM, CCoAOMT, 4CL, PAL, CCR, CSE, and CADH, involved in the synthesis of plant antitoxins such as flavonoids, stilbenoids, and lignins, enriched in the phenylpropane pathway were upregulated at 3 and 7 dpi. Furthermore, a pot experiment was performed to verify the role of flavonoids in controlling TBW. This study will strongly contribute to a better understanding of molecular interactions between tobacco plants and R. solanacearum.
Highlights
Tobacco bacterial wilt (TBW) caused by Ralstonia solanacearum is the most serious soil-borne disease of tobacco
Through the transcriptome analysis of resistant and susceptible tomato cultivar after inoculation with R. solanacearum, more than 140 genes related to pathogenesis, hormone signaling, and lignin biosynthesis were increased in resistant cultivar, but no change found in susceptible c ultivar[6]
When seedlings grew to the 5–6 leaf stage, the wounded roots of resistant and susceptible cultivars were inoculated with HBLC5 suspension (1 × 108 CFU/mL) (OD600 = 0.1), according to the method suggested by Cellier and Prior[24]
Summary
Tobacco bacterial wilt (TBW) caused by Ralstonia solanacearum is the most serious soil-borne disease of tobacco. The expression profiles of the rootstalks of Yunyan[87] (susceptible cultivar) and Fandi[3] (resistant cultivar) at different stages after R. solanacearum infection were compared to explore molecular mechanisms of tobacco resistance against the bacterium. Tobacco bacterial wilt (TBW), caused by R. solanacearum, is the most serious soil-borne disease in tobacco plants. 81 differentially expressed genes were considered R. solanacearum resistance-related genes, and these genes played putative roles in pathogen recognition, signal transduction, transcription factor functioning, hypersensitive response, systemic acquired resistance, cell rescue, and protection[5]. Profiling on resistant and susceptible peanut roots under R. solanacearum infection They found that many unique genes were mainly involved in phytoalexins’ biosynthesis, in the biosynthetic pathways of terpenoids and flavonoids. In PTI, WRKY transcription factors (WRKY TFs) and ethylene-responsive TFs (ERF TFs) play important roles as regulators of plant immunity against phytopathogen, which are regulated by signaling synergistically mediated by ethylene (ET), jasmonic acid (JA), and salicylic acid (SA) signaling p athways[7,11,12,13,14,15,16,17,18,19,20,21,22,23]
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