Abstract
Bacterial spot (BS), incited by Xanthomonas campestris pv. vesicatoria (Xcv), is one of the most serious diseases of pepper. For a comparative analysis of defense responses to Xcv infection, we performed a transcriptomic analysis of a susceptible cultivar, ECW, and a resistant cultivar, VI037601, using the HiSeqTM 2500 sequencing platform. Approximately 120.23 G clean bases were generated from 18 libraries. From the libraries generated, a total of 38,269 expressed genes containing 11,714 novel genes and 11,232 differentially expressed genes (DEGs) were identified. Functional enrichment analysis revealed that the most noticeable pathways were plant-pathogen interaction, MAPK signaling pathway—plant, plant hormone signal transduction and secondary metabolisms. 1,599 potentially defense-related genes linked to pattern recognition receptors (PRRs), mitogen-activated protein kinase (MAPK), calcium signaling, and transcription factors may regulate pepper resistance to Xcv. Moreover, after Xcv inoculation, 364 DEGs differentially expressed only in VI037601 and 852 genes in both ECW and VI037601. Many of those genes were classified as NBS-LRR genes, oxidoreductase gene, WRKY and NAC transcription factors, and they were mainly involved in metabolic process, response to stimulus and biological regulation pathways. Quantitative RT-PCR of sixteen selected DEGs further validated the RNA-seq differential gene expression analysis. Our results will provide a valuable resource for understanding the molecular mechanisms of pepper resistance to Xcv infection and improving pepper resistance cultivars against Xcv.
Highlights
Bell pepper (Capsicum annuum L.), an important member of the Solanaceae family, is one of the most important vegetable crops in China and many other countries [1]
Transcriptome analysis of pepper in response to Xanthomonas campestris pv. vesicatoria symptom was observed in VI037601 containing the R gene Bs1 at 24 hpi, whereas cultivar Early Calwonder (ECW) presented no hypersensitive response (HR) symptom at either timepoints, indicating that VI037601 and ECW may have different responses to Xcv infection at the transcriptome level (Fig 1)
Many “Metabolism process” were enriched in 24 hpi in ECW and VI0378601, such as carbon metabolism, biosynthesis of amino acids, starch and sucrose metabolism, arginine and proline metabolism, and porphyrin and chlorophyll metabolism (Fig 4 and S7 Table). These results indicated that the different expression patterns of differentially expressed genes (DEGs) in significant Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway categories in ECW and VI037601 helped to determine the functions of DEGs and screen of candidate resistance genes, which was responsible for the resistance to Xcv in VI037601
Summary
Bell pepper (Capsicum annuum L.), an important member of the Solanaceae family, is one of the most important vegetable crops in China and many other countries [1]. Transcriptome analysis of pepper in response to Xanthomonas campestris pv. Science Foundation of Hubei Province (2020CFA010) and Youth Fund of Hubei Academy of Agricultural Sciences (2021NKYJJ04). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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