Legumes form symbiosis with rhizobia, which fix nitrogen for the benefit of host plant in return for carbon resources. Development of this unique symbiosis in legumes is triggered by rhizobia-secreted nodulation (Nod) factors (NFs). NFs, upon perception, activate Nod signaling cascade, leading to reprogramming of host cell (root) developmental networks to pave way for accommodating rhizobial symbionts. A long-cherished goal of legume-rhizobia symbiosis research is to extend this symbiotic nitrogen-fixing capacity to cereal plants such as rice. As a part of achieving this ultimate goal, in this work, initially we expressed legume-specific Nod factor receptor protein (NFRP) genes, MtNFP , MtLYK3 , and LjLNP , in rice and assessed their impact on NF perception and consequently triggered biological responses in roots. RNA-seq analysis revealed that roots of both control and NFRP-expressing plants perceive NFs, but NFs elicited contrasting impacts on gene expression patterns in roots of these plants. In contrast to suppressive role of NFs on expression of several genes involved in innate immune response in roots of control plants, in NFRP-expressing plants, NFs triggered massive upregulation of a vast array of genes associated with signaling, defense response, and secondary metabolism networks in roots. Expression of NFRPs in rice also conferred root hairs the ability to respond to NFs in terms of exhibiting deformations, albeit at low levels. Together, results of the study demonstrated that rice plants have inherent ability to perceive NFs, but the expression of legume NFRPs rendered rice roots hypersensitive to NFs.

中文翻译：

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豆科植物特异性 Nod 因子受体蛋白的表达改变水稻的发育和免疫反应

豆科植物与根瘤菌形成共生关系，根瘤菌固氮造福寄主植物，以换取碳资源。豆科植物中这种独特共生的发展是由根瘤菌分泌的结瘤 (Nod) 因子 (NFs) 引发的。NFs 在感知时激活 Nod 信号级联，导致宿主细胞（根）发育网络的重新编程，为容纳根瘤菌共生体铺平道路。豆科植物根瘤菌共生研究的一个长期目标是将这种共生固氮能力扩展到水稻等谷类植物。作为实现这一最终目标的一部分，在这项工作中，最初我们在水稻中表达了豆科植物特异性 Nod 因子受体蛋白 (NFRP) 基因 MtNFP、MtLYK3 和 LjLNP，并评估了它们对 NF 感知的影响，从而在根。RNA-seq 分析显示，对照和表达 NFRP 的植物的根都感知 NF，但 NF 对这些植物根中的基因表达模式产生了截然不同的影响。与 NFs 对对照植物根部先天免疫反应相关基因表达的抑制作用相反，在表达 NFRP 的植物中，NFs 引发了大量与信号传导、防御反应和次级代谢网络相关的基因的大量上调在根。NFRPs 在水稻中的表达也赋予了根毛在表现出变形方面对 NFs 做出反应的能力，尽管水平很低。总之，研究结果表明，水稻植物具有感知 NFs 的固有能力，但豆科植物 NFRPs 的表达使水稻根部对 NFs 过敏。