Legume Genomics Laboratory, National Institute of Plant Genome Research, New Delhi, India.
Plant Cell Environ. 2021 May;44(5):1279-1291. doi: 10.1111/pce.13983. Epub 2021 Jan 13.
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.
共生固氮在氮素供应不足的土壤中对豆科植物很重要。共生的起始和维持需要细胞重编程，这涉及 miRNA 介导的特定结瘤基因的抑制或激活。小 RNA 文库的高通量测序已经鉴定出 miRNA 及其靶标，它们是豆科植物-根瘤菌共生不同阶段（从细菌定殖和器官发生到共生固氮）的转录后基因调控（PTGS）的主要参与者。在这里，我们概述了迄今为止从已测序的结瘤组织的 miRNA 文库中获得的信息。miRNA 的功能分析揭示了它们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 shoot to root 信号转导中的功能，影响包括细菌进入、分生组织分裂和分化、固氮和衰老在内的多种功能。此外，根瘤菌来源的小 RNA 片段可以抑制植物互补 mRNA。我们还考虑了 miRNA 在定殖或不定殖结瘤中的作用。总之，这一综述证实了 miRNA 是豆科植物-根瘤菌共生的主要调控因子。
