Symbiotic nitrogen fixation is benefit to sustainable agriculture and global nitrogen cycle. Many small peptides were identified as regulators involving in the interaction between rhizobia and legume. Here we reported Nodule Rich Protein 2 (MtNRP2) encoding a small peptide in Medicago truncatula, belonged to a group of nodule rich protein restricted in legume species. MtNRP2 expressed highly in root nodule and its promoter was active during the initiation and development of root nodule and lateral root. To investigate the function of MtNRP2 in nodulation, we generated MtNRP2-overexpression and MtNRP2-knockdown transgenic Medicago. MtNRP2-overexpression transgenic lines performed normal nodulation phenotype compared with vector control. However, in the MtNRP2-RNAi transgenic plants, the decrease of MtNRP2 expression lead to the increase of infection threads number (7 day post inoculation) and nodules number (3 week post inoculation); meanwhile, the expression of MtRGF3 and MtPUB1 was inhibited. These results suggested that MtNRP2 negatively regulated nodulation in Medicago truncatula.

共生固氮有利于可持续农业和全球氮循环。许多小肽被鉴定为参与根瘤菌和豆类之间相互作用的调节剂。在这里，我们报道了在苜蓿run藜中编码一个小肽的富含结核的蛋白质2（MtNRP2），属于一组受豆类限制的富含结核的蛋白质。MtNRP2在根瘤中高表达，其启动子在根瘤和侧根的起始和发育过程中具有活性。为了研究MtNRP2在结瘤中的功能，我们生成了MtNRP2过表达和MtNRP2基因敲低的转基因苜蓿。与载体对照相比，MtNRP2-过表达转基因品系表现出正常的结节表型。然而，在MtNRP2-RNAi转基因植物中，MtNRP2表达的减少导致感染线数（接种后7天）和结节数（接种后3周）的增加。同时，MtRGF3和MtPUB1的表达受到抑制。这些结果表明，MtNRP2负调节苜蓿的结节。