Division of Plant Biology, Unified Academic Campus, Bose Institute, EN 80, Bidhan Nagar, Kolkata, West Bengal, 700091, India.
Division of Bioinformatics, Unified Academic Campus, Bose Institute, EN 80, Bidhan Nagar, Kolkata, West Bengal, 700091, India.
Plant Mol Biol. 2022 Aug;109(6):717-739. doi: 10.1007/s11103-022-01270-z. Epub 2022 May 2.
miR6024 acts as a negative regulator of R genes, hence of Tomato plant immunity, and facilitates disease by the necrotrophic pathogen A. solani. Plant resistance genes or Nucleotide-binding leucine-rich repeat (NLR) genes, integral components of plant disease stress-signaling are targeted by variable groups of miRNAs. However, the significance of miRNA-mediated regulation of NLRs during a pathogen stress response, specifically for necrotrophic fungus, is poorly understood. A thorough examination of Tomato NLRs and miRNAs could map substantial interactions of which half the annotated NLRs were targets of Solanaceae-specific and conserved miRNAs, at the NB subdomain. The Solanaceae-specific miR6024 and its NLR targets analysed in different phytopathogenic stresses revealed differential and mutually antagonistic regulation. Interestingly, miR6024-targeted cleavage of a target NLR also triggered the generation of secondary phased siRNAs which could potentially amplify the defense signal. RNA-seq analysis of leaf tissues from miR6024 overexpressing Tomato plants evidenced a perturbation in the defense transcriptome with the transgenics showing unwarranted immune response-related genes' expression with or without infection with necrotrophic Alternaria solani, though no adverse effect could be observed in the growth and development of the transgenic plants. Transgenic plants exhibited constitutive downregulation of the target NLRs, aggravated disease phenotype with an enhanced lesion, greater ROS generation and hypersusceptibility to A. solani infection, thus establishing that miR6024 negatively impacts plant immune response during necrotrophic pathogenesis. Limited knowledge about the outcome of NLR-miRNA interaction during necrotrophic pathogenesis is a hindrance to the deployment of miRNAs in crop improvement programs. With the elucidation of the necrotrophic disease-synergistic role played by miR6024, it becomes a potent candidate for biotechnological manipulation for the rapid development of pathogen-tolerant solanaceous plants.
miR6024 作为 R 基因的负调控因子，因此影响番茄植物的免疫，促进了坏死型病原体 A. solani 的病害。植物抗性基因或核苷酸结合富含亮氨酸重复（NLR）基因是植物疾病胁迫信号的组成部分，可变的 miRNA 组靶向这些基因。然而，miRNA 介导的 NLR 调控在病原体胁迫反应中的意义，特别是对于坏死型真菌，还知之甚少。对番茄 NLR 和 miRNA 的全面研究可以映射出大量的相互作用，其中一半注释的 NLR 是茄科特异性和保守 miRNA 的靶点，位于 NB 亚结构域。在不同的植物病理胁迫下分析的茄科特异性 miR6024 和其 NLR 靶标揭示了差异和相互拮抗的调控。有趣的是，miR6024 靶向切割一个靶标 NLR 也触发了二级相 siRNA 的产生，这可能放大防御信号。miR6024 过表达番茄叶片组织的 RNA-seq 分析表明，防御转录组发生了扰动，转基因植物表现出不必要的免疫相关基因表达，无论是否感染坏死型 Alternaria solani，但在转基因植物的生长和发育中没有观察到不良影响。转基因植物表现出靶标 NLR 的组成性下调，加剧了病害表型，出现更大的损伤、更多的 ROS 生成和对 A. solani 感染的超敏性，从而确立了 miR6024 在坏死型发病过程中对植物免疫反应的负面影响。在坏死型发病过程中 NLR-miRNA 相互作用的结果知之甚少，这阻碍了 miRNA 在作物改良计划中的应用。随着 miR6024 在坏死型病害协同作用的阐明，它成为生物技术操作的有力候选者，可用于快速开发对病原体耐受的茄科植物。
