Legumes control their nodule numbers through the autoregulation of nodulation (AON). Rhizobia infection stimulates the production of root‐derived CLE peptide hormones that are translocated to the shoot where they regulate a new signal. We used soybean to demonstrate that this shoot‐derived signal is miR2111, which is transported via phloem to the root where it targets transcripts of Too Much Love (TML), a negative regulator of nodulation. Shoot perception of rhizobia‐induced CLE peptides suppresses miR2111 expression, resulting in TML accumulation in roots and subsequent inhibition of nodule organogenesis. Feeding synthetic mature miR2111 via the petiole increased nodule numbers per plant. Likewise, elevating miR2111 availability by over‐expression promoted nodulation, while target mimicry of TML induced the opposite effect on nodule development in wild‐type plants and alleviated the supernodulating and stunted root growth phenotypes of AON‐defective mutants. Additionally, in non‐nodulating wild‐type plants, ectopic expression of miR2111 significantly enhanced lateral root emergence with a decrease in lateral root length and average root diameter. In contrast, hairy roots constitutively expressing the target mimic construct exhibited reduced lateral root density. Overall, these findings demonstrate that miR2111 is both the critical shoot‐to‐root factor that positively regulates root nodule development and also acts to shape root system architecture.

中文翻译：

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芽源性 miR2111 控制豆科植物根和根瘤的发育


豆类通过结瘤自动调节（AON）来控制其根瘤数量。根瘤菌感染会刺激根源性 CLE 肽激素的产生，这些激素会转移到芽中，在那里调节新信号。我们使用大豆来证明这种芽源信号是 miR2111，它通过韧皮部转运到根，在那里它的目标是Too Much Love ( TML ) 的转录本，TML 是结瘤的负调节因子。根瘤菌诱导的 CLE 肽的芽感知抑制 miR2111 表达，导致 TML 在根中积累，并随后抑制根瘤器官发生。通过叶柄饲喂合成的成熟 miR2111 增加了每株植物的根瘤数量。同样，通过过度表达提高 miR2111 的可用性促进了结瘤，而TML的靶拟态则对野生型植物的根瘤发育产生相反的影响，并减轻了 AON 缺陷突变体的超结瘤和根生长发育迟缓的表型。此外，在非结瘤野生型植物中，miR2111的异位表达显着增强了侧根的出现，同时侧根长度和平均根直径减小。相反，组成型表达目标模拟构建体的毛状根表现出侧根密度降低。总的来说，这些发现表明 miR2111 既是关键的从芽到根的因子，可以积极调节根瘤发育，也可以塑造根系结构。