Department of Biology, University of Copenhagen, Copenhagen N, DK-2200, Denmark.
Instituto de Hortofruticultura Subtropical y Mediterránea 'La Mayora', Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto. Biología Celular, Genética y Fisiología, Málaga, Spain.
J Exp Bot. 2023 Oct 13;74(19):6052-6068. doi: 10.1093/jxb/erad268.
Plants use different receptors to detect potential pathogens: membrane-anchored pattern recognition receptors (PRRs) activated upon perception of pathogen-associated molecular patterns (PAMPs) that elicit pattern-triggered immunity (PTI); and intracellular nucleotide-binding leucine-rich repeat proteins (NLRs) activated by detection of pathogen-derived effectors, activating effector-triggered immunity (ETI). The interconnections between PTI and ETI responses have been increasingly reported. Elevated NLR levels may cause autoimmunity, with symptoms ranging from fitness cost to developmental arrest, sometimes combined with run-away cell death, making accurate control of NLR dosage key for plant survival. Small RNA-mediated gene regulation has emerged as a major mechanism of control of NLR dosage. Twenty-two nucleotide miRNAs with the unique ability to trigger secondary siRNA production from target transcripts are particularly prevalent in NLR regulation. They enhance repression of the primary NLR target, but also bring about repression of NLRs only complementary to secondary siRNAs. We summarize current knowledge on miRNAs and siRNAs in the regulation of NLR expression with an emphasis on 22 nt miRNAs and propose that miRNA and siRNA regulation of NLR levels provides additional links between PTI and NLR defense pathways to increase plant responsiveness against a broad spectrum of pathogens and control an efficient deployment of defenses.
膜锚定的模式识别受体（PRR），在感知到病原体相关分子模式（PAMP）时被激活，引发模式触发免疫（PTI）；以及细胞内核苷酸结合富含亮氨酸重复蛋白（NLR），通过检测病原体衍生的效应物而被激活，引发效应触发免疫（ETI）。PTI 和 ETI 反应之间的相互联系已被越来越多地报道。NLR 水平的升高可能导致自身免疫，症状从适应度降低到发育停滞，有时伴有失控的细胞死亡，因此准确控制 NLR 剂量对植物的生存至关重要。小 RNA 介导的基因调控已成为控制 NLR 剂量的主要机制。具有从靶标转录本中引发二次 siRNA 产生的独特能力的 22 个核苷酸 miRNA 在 NLR 调控中尤为普遍。它们增强了对初级 NLR 靶标的抑制，但也仅对与二次 siRNA 互补的 NLR 产生抑制作用。我们总结了 miRNA 和 siRNA 在 NLR 表达调控中的最新知识，重点介绍了 22 个核苷酸的 miRNA，并提出 miRNA 和 siRNA 对 NLR 水平的调控为 PTI 和 NLR 防御途径之间提供了额外的联系，以提高植物对广谱病原体的反应能力，并控制防御的有效部署。
