Root nodule symbiosis (RNS) between legumes and rhizobia is a major source of nitrogen in agricultural systems. Effective symbiosis requires precise regulation of plant defense responses. The role of the defense hormone jasmonic acid (JA) in the immune response has been extensively studied. Current research shows that JA can play either a positive or negative regulatory role in RNS depending on its concentration, but the molecular mechanisms remain to be elucidated. In this study, we found that inoculation with the rhizobia induces the JA pathway in , and blocking the JA pathway significantly reduces the number of infection threads. Mutations in the gene, which encodes a JA signaling master transcription factor, significantly inhibited rhizobia infection, terminal differentiation, and symbiotic cell formation. Combining RNA sequencing and chromatin immunoprecipitation sequencing, we discovered that MtMYC2 regulates the expression of nodule-specific , , and to suppress host defense, while it activates expression to regulate the maturation of MtNCRs, which in turn promotes bacteroid formation. More importantly, MtMYC2 participates in symbiotic signal transduction by promoting the expression of . Notably, the MtMYC2-MtIPD3 transcriptional regulatory module is specifically present in legumes, and the mutants are susceptible to the infection by the pathogen . Collectively, these findings reveal the molecular mechanisms of how the JA pathway regulates RNS, broadening our understanding of the roles of JA in plant-microbe interactions.

中文翻译：

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茉莉酸途径促进蒺藜苜蓿根瘤共生并抑制宿主植物防御


豆科植物和根瘤菌之间的根瘤共生（RNS）是农业系统中氮的主要来源。有效的共生需要精确调节植物防御反应。防御激素茉莉酸（JA）在免疫反应中的作用已被广泛研究。目前的研究表明，JA 可以根据其浓度对 RNS 发挥正向或负向调节作用，但其分子机制仍有待阐明。在这项研究中，我们发现接种根瘤菌会诱导JA途径，并且阻断JA途径会显着减少感染线的数量。编码 JA 信号主转录因子的基因突变显着抑制根瘤菌感染、终末分化和共生细胞形成。结合RNA测序和染色质免疫沉淀测序，我们发现MtMYC2调节结节特异性的表达，抑制宿主防御，同时激活表达来调节MtNCR的成熟，进而促进类菌体的形成。更重要的是，MtMYC2通过促进.的表达参与共生信号转导。值得注意的是，MtMYC2-MtIPD3转录调控模块特异存在于豆科植物中，突变体容易受到病原体的感染。总的来说，这些发现揭示了 JA 途径调节 RNS 的分子机制，拓宽了我们对 JA 在植物-微生物相互作用中作用的理解。