Plant genomes contain two major classes of innate immune receptors to recognize different pathogens. The pattern recognition receptors perceive conserved pathogen-associated molecular patterns and the resistance genes with nucleotide-binding (NB) and leucine-rich repeat (LRR) domains recognize specific pathogen effectors. The precise regulation of resistance genes is important since the unregulated expression of NB-LRR genes can inhibit growth and may result in autoimmunity in the absence of pathogen infection. It was shown that a subset of miRNAs could target NB-LRR genes and act as an important regulator of plant immunity in the absence of pathogens. Plants not only interact with pathogens, but they can also establish symbiotic interactions with microbes. Nitrogen-fixing symbiotic interaction and nodule formation of legumes may also require the suppression of host defence to prevent immune responses. We found that upon symbiotic interactions, miRNAs repressing NB-LRR expression are upregulated in the developing nodules of Medicago truncatula. Furthermore, we show that the suppression of the activity of the NB-LRR genes targeted by these miRNAs is important during nodule development. Our results suggest that the downregulation of NB-LRR resistance genes in the developing nodule produces a suitable niche that facilitates bacterial colonization and the development of an N-fixing nodule.

中文翻译：

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miRNA抑制NB-LRR基因可促进Medi藜苜蓿中固氮根瘤的发育。

植物基因组包含两大类先天免疫受体，以识别不同的病原体。模式识别受体感知到保守的病原体相关分子模式，具有核苷酸结合（NB）和富亮氨酸重复序列（LRR）结构域的抗性基因识别特定的病原体效应物。耐药基因的精确调控非常重要，因为NB-LRR基因的不受调控的表达会抑制生长，并可能在没有病原体感染的情况下导致自身免疫。结果表明，在没有病原体的情况下，miRNA的一个子集可以靶向NB-LRR基因，并作为植物免疫力的重要调节剂。植物不仅与病原体相互作用，而且还可以与微生物建立共生相互作用。豆科植物固氮共生相互作用和根瘤形成也可能需要抑制宿主防御，以防止免疫反应。我们发现，在共生相互作用中，抑制NB-LRR表达的miRNA在Medi藜苜蓿的发育结节中被上调。此外，我们表明，在这些结节发育过程中，抑制由这些miRNA靶向的NB-LRR基因的活性很重要。我们的结果表明，正在发育的根瘤中NB-LRR抗性基因的下调产生了合适的生态位，有利于细菌定居和固氮结节的发展。我们表明抑制这些miRNA靶向的NB-LRR基因的活性在结节发育过程中很重要。我们的结果表明，正在发育的根瘤中NB-LRR抗性基因的下调产生了合适的生态位，有利于细菌定居和固氮结节的发展。我们表明抑制这些miRNA靶向的NB-LRR基因的活性在结节发育过程中很重要。我们的结果表明，正在发育的根瘤中NB-LRR抗性基因的下调产生了合适的生态位，有利于细菌定居和固氮结节的发展。