Symbiotic nitrogen fixation in legume nodules is important in soils with low nitrogen availability. The initiation and sustainability of symbiosis require cellular reprogramming that involves the miRNA‐mediated inhibition or activation of specific nodulation genes. The high‐throughput sequencing of small RNA libraries has identified miRNAs and their targets, which are the major players in the post‐transcriptional gene regulation (PTGS) of the different stages of legume–rhizobia symbiosis ranging from bacterial colonization and organogenesis to symbiotic nitrogen fixation. Here, we present an overview of information obtained from the miRNA libraries from nodulating tissues that have been sequenced to date. The functional analysis of miRNAs has revealed roles in phytohormone homeostasis and spatio‐temporal regulation, as well as the mobility of miRNAs and their functions in shoot to root signalling that affects diverse functions, including bacterial entry, meristem division and differentiation, nitrogen fixation and senescence. Furthermore, small RNA fragments of rhizobial origin repress complementary plant mRNAs. We also consider the roles of miRNAs in determinate or indeterminate nodules. Taken together, this overview confirms that miRNAs are master regulators of the legume–rhizobia symbiosis.

中文翻译：

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miRNA介导的豆科植物共生调控动力学

豆科植物根瘤中的共生固氮在氮可用性低的土壤中很重要。共生的启动和可持续性需要细胞重编程，包括 miRNA 介导的抑制或激活特定结瘤基因。小 RNA 文库的高通量测序已经确定了 miRNA 及其靶标，它们是豆科植物-根瘤菌共生不同阶段的转录后基因调控 (PTGS) 的主要参与者，从细菌定植和器官发生到共生固氮. 在这里，我们概述了从迄今为止已测序的结节组织的 miRNA 文库中获得的信息。miRNA 的功能分析揭示了在植物激素稳态和时空调节中的作用，以及 miRNA 的移动性及其在芽到根信号传导中的功能，这些信号会影响多种功能，包括细菌进入、分生组织分裂和分化、固氮和衰老。此外，根瘤菌来源的小 RNA 片段会抑制互补的植物 mRNA。我们还考虑了 miRNA 在确定或不确定结节中的作用。综上所述，该概述证实 miRNA 是豆科植物 - 根瘤菌共生的主要调节因子。