• Legumes form a symbiosis with atmospheric nitrogen (N₂)‐fixing soil rhizobia, resulting in new root organs called nodules that enable N₂‐fixation. Nodulation is a costly process that is tightly regulated by the host through autoregulation of nodulation (AON) and nitrate‐dependent regulation of nodulation. Both pathways require legume‐specific CLAVATA/ESR‐related (CLE) peptides.
• Nitrogen‐induced nodulation‐suppressing CLE peptides have not previously been investigated in Medicago truncatula, for which only rhizobia‐induced MtCLE12 and MtCLE13 have been characterised. Here, we report on novel peptides MtCLE34 and MtCLE35 in nodulation control.
• The nodulation‐suppressing CLE peptides of five legume species were classified into three clades based on sequence homology and phylogeny. This approached identified MtCLE34 and MtCLE35 and four new CLE peptide orthologues of Pisum sativum. Whereas MtCLE12 and MtCLE13 are induced by rhizobia, MtCLE34 and MtCLE35 respond to both rhizobia and nitrate. MtCLE34 was identified as a pseudogene lacking a functional CLE‐domain. MtCLE35 was found to inhibit nodulation in a SUNN‐ and RDN1‐dependent manner via overexpression analysis.
• Together, our findings indicate that MtCLE12 and MtCLE13 have a specific role in AON, while MtCLE35 regulates nodule numbers in response to both rhizobia and nitrate. MtCLE34 likely had a similar role to MtCLE35, but its function was lost due to a premature nonsense mutation.

中文翻译：

---

run藜CLE34和CLE35在硝化和根瘤菌调节结瘤中的特性

• 豆科植物与固定氮（N ₂）的土壤根瘤菌形成共生关系，产生了称为根瘤的新根器官，从而使N ₂得以固定。结瘤是一个昂贵的过程，宿主会通过结瘤的自动调节（AON）和硝酸盐依赖性的结瘤调节来严格调节。两种途径都需要豆科植物特异性的CLAVATA / ESR相关（CLE）肽。
• 之前未在Medi藜苜蓿中研究过氮诱导的抑制结瘤的CLE肽，对此仅鉴定了根瘤菌诱导的MtCLE12和MtCLE13。在这里，我们报告结瘤对照中的新型肽MtCLE34和MtCLE35。
• 根据序列同源性和系统发育，将五个豆科植物抑制结节的CLE肽分为三个进化枝。这走近确定MtCLE34和MtCLE35和四个新的CLE肽同源基因豌豆。而MtCLE12和MtCLE13由根瘤菌，诱导MtCLE34和MtCLE35响应这两个根瘤菌和硝酸盐。MtCLE34被鉴定为缺乏功能性CLE域的假基因。通过过度表达分析，发现MtCLE35以SUNN和RDN1依赖性方式抑制结节。
• 总之，我们的发现表明MtCLE12和MtCLE13在AON中具有特定作用，而MtCLE35调节根瘤菌和硝酸盐的根瘤数。MtCLE34可能具有与MtCLE35类似的作用，但由于过早的无意义突变而使其功能丧失。