Plant Science Research Unit, United States Department of Agriculture, St Paul, MN, 55108, USA.
Department of Plant Pathology, University of Minnesota, St. Paul, MN, 55108, USA.
BMC Plant Biol. 2024 Jul 29;24(1):720. doi: 10.1186/s12870-024-05444-3.
Ascochyta blights cause yield losses in all major legume crops. Spring black stem (SBS) and leaf spot disease is a major foliar disease of Medicago truncatula and Medicago sativa (alfalfa) caused by the necrotrophic fungus Ascochyta medicaginicola. This present study sought to identify candidate genes for SBS disease resistance for future functional validation. We employed RNA-seq to profile the transcriptomes of a resistant (HM078) and susceptible (A17) genotype of M. truncatula at 24, 48, and 72 h post inoculation. Preliminary microscopic examination showed reduced pathogen growth on the resistant genotype. In total, 192 and 2,908 differentially expressed genes (DEGs) were observed in the resistant and susceptible genotype, respectively. Functional enrichment analysis revealed the susceptible genotype engaged in processes in the cell periphery and plasma membrane, as well as flavonoid biosynthesis whereas the resistant genotype utilized calcium ion binding, cell wall modifications, and external encapsulating structures. Candidate genes for disease resistance were selected based on the following criteria; among the top ten upregulated or downregulated genes in the resistant genotype, upregulated over time in the resistant genotype, hormone pathway genes, plant disease resistance genes, receptor-like kinases, contrasting expression profiles in QTL for disease resistance, and upregulated genes in enriched pathways. Overall, 22 candidate genes for SBS disease resistance were identified with support from the literature. These genes will be sources for future targeted mutagenesis and candidate gene validation potentially helping to improve disease resistance to this devastating foliar pathogen.
茎点霉叶斑病导致所有主要豆科作物减产。春黑茎（SBS）和叶斑病是蒺藜苜蓿和紫花苜蓿（紫花苜蓿）的一种主要叶部病害，由坏死型真菌 Ascochyta medicaginicola 引起。本研究旨在鉴定 SBS 抗病候选基因，以便未来进行功能验证。我们采用 RNA-seq 技术在接种后 24、48 和 72 小时分别对蒺藜苜蓿抗性（HM078）和感病（A17）基因型进行转录组分析。初步显微镜检查表明，病原菌在抗性基因型上的生长减少。在抗性和感病基因型中分别观察到 192 和 2908 个差异表达基因（DEGs）。功能富集分析表明，感病基因型参与了细胞外围和质膜以及类黄酮生物合成过程，而抗性基因型则利用钙离子结合、细胞壁修饰和外部包裹结构。根据以下标准选择抗病候选基因；在抗性基因型中上调基因前 10 位或下调基因前 10 位中，在抗性基因型中随时间上调，激素途径基因、植物抗病基因、类受体激酶、与抗病 QTL 相反的表达谱和富集途径中上调的基因。总体而言，从文献中确定了 22 个 SBS 抗病候选基因。这些基因将成为未来靶向诱变和候选基因验证的来源，有助于提高对这种破坏性叶部病原体的抗病性。
