Abstract
Banana Xanthomonas wilt disease, caused by Xanthomonas campestris pv. musacearum (Xcm), is a major threat to banana production in east Africa. All cultivated varieties of banana are susceptible to Xcm and only the progenitor species Musa balbisiana was found to be resistant. The molecular basis of susceptibility and resistance of banana genotypes to Xcm is currently unknown. Transcriptome analysis of disease resistant genotype Musa balbisiana and highly susceptible banana cultivar Pisang Awak challenged with Xcm was performed to understand the disease response. The number of differentially expressed genes (DEGs) was higher in Musa balbisiana in comparison to Pisang Awak. Genes associated with response to biotic stress were up-regulated in Musa balbisiana. The DEGs were further mapped to the biotic stress pathways. Our results suggested activation of both PAMP-triggered basal defense and disease resistance (R) protein-mediated defense in Musa balbisiana as early response to Xcm infection. This study reports the first comparative transcriptome profile of the susceptible and resistant genotype of banana during early infection with Xcm and provide insights on the defense mechanism in Musa balbisiana, which can be used for genetic improvement of commonly cultivated banana varieties.
Highlights
RNA sequencing (RNA-Seq) data from Xanthomonas campestris pv. musacearum (Xcm) challenged and mock-inoculated BXW-susceptible banana genotype Pisang Awak and BXW-resistant genotype Musa balbisiana were analyzed for transcriptome comparison
The differential expression was confirmed by quantitative RT- PCR (qRT-PCR) for some of the genes involved in plant defense such as antimicrobial peptide vicilin, R genes (RPM1, leucine-rich repeat (LRR) disease resistance family), PR genes, transcription factors (MYB, MADS-box, WRKY), receptor like kinases, redox associated genes, genes involved in signaling pathways, E3 ubiquitin ligase and germin-like protein
Transcriptome profiles of BXW-resistant and BXW-susceptible banana genotypes challenged with Xcm were compared to better understand molecular mechanism of resistance or susceptibility of banana upon bacterial infection
Summary
RNA-Seq data from Xcm challenged and mock-inoculated BXW-susceptible banana genotype Pisang Awak and BXW-resistant genotype Musa balbisiana were analyzed for transcriptome comparison. The numbers of DEGs were higher in BXW-resistant genotype Musa balbisiana in comparison to BXW-susceptible genotype Pisang Awak at both 12 hpi (1749 vs 4) and 48 hpi (245 vs 88) (Fig. 1A, Supplementary Tables S1–S4). The number of DEGs for Musa balbisiana was considerably higher at 12 hpi in comparison to 48 hpi (1749 vs 245), in contrast a greater number of genes were differentially expressed at 48 hpi than at 12 hpi in Pisang Awak (88 vs 4) (Fig. 1B). More number of genes were differentially expressed in BXW-resistant genotype in comparison to BXW-susceptible genotype due to interaction with Xcm at different time post inoculation (Table 1).
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