National Institute for Basic Biology, Nishigonaka 38, Myodaiji, Okazaki 444-8585, Japan.
Nat Commun. 2013;4:2191. doi: 10.1038/ncomms3191.
Leguminous plants establish a symbiosis with rhizobia to enable nitrogen fixation in root nodules under the control of the presumed root-to-shoot-to-root negative feedback called autoregulation of nodulation. In Lotus japonicus, autoregulation is mediated by CLE-RS genes that are specifically expressed in the root, and the receptor kinase HAR1 that functions in the shoot. However, the mature functional structures of CLE-RS gene products and the molecular nature of CLE-RS/HAR1 signalling governed by these spatially distant components remain elusive. Here we show that CLE-RS2 is a post-translationally arabinosylated glycopeptide derived from the CLE domain. Chemically synthesized CLE-RS glycopeptides cause significant suppression of nodulation and directly bind to HAR1 in an arabinose-chain and sequence-dependent manner. In addition, CLE-RS2 glycopeptide specifically produced in the root is found in xylem sap collected from the shoot. We propose that CLE-RS glycopeptides are the long sought mobile signals responsible for the initial step of autoregulation of nodulation.
豆科植物与根瘤菌形成共生关系，在假定的根到茎到根的负反馈（称为共生的自我调控）控制下，在根瘤中实现氮固定。在百脉根中，自我调控是由CLE-RS 基因介导的，这些基因特异性地在根中表达，而受体激酶 HAR1 在茎中发挥作用。然而，CLE-RS 基因产物的成熟功能结构以及由这些空间上遥远的成分控制的 CLE-RS/HAR1 信号的分子性质仍然难以捉摸。在这里，我们表明 CLE-RS2 是一种翻译后阿拉伯糖基化糖肽，来源于 CLE 结构域。化学合成的 CLE-RS 糖肽会显著抑制结瘤，并以阿拉伯糖链和序列依赖性的方式直接与 HAR1 结合。此外，在根中特异性产生的 CLE-RS2 糖肽在从茎中收集的木质部汁液中被发现。我们提出，CLE-RS 糖肽是长期以来一直寻找的负责共生的自我调控的初始步骤的可移动信号。
