Division of Plant Sciences, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra ACT 0200, Australia.
J Exp Bot. 2013 Dec;64(17):5395-409. doi: 10.1093/jxb/ert369.
The role of MtCEP1, a member of the CEP (C-terminally encoded peptide) signaling peptide family, was examined in Medicago truncatula root development. MtCEP1 was expressed in root tips, vascular tissue, and young lateral organs, and was up-regulated by low nitrogen levels and, independently, by elevated CO2. Overexpressing MtCEP1 or applying MtCEP1 peptide to roots elicited developmental phenotypes: inhibition of lateral root formation, enhancement of nodulation, and the induction of periodic circumferential root swellings, which arose from cortical, epidermal, and pericycle cell divisions and featured an additional cortical cell layer. MtCEP peptide addition to other legume species induced similar phenotypes. The enhancement of nodulation by MtCEP1 is partially tolerant to high nitrate, which normally strongly suppresses nodulation. These nodules develop faster, are larger, and fix more nitrogen in the absence and presence of inhibiting nitrate levels. At 25mM nitrate, nodules formed on pre-existing swelling sites induced by MtCEP1 overexpression. RNA interference-mediated silencing of several MtCEP genes revealed a negative correlation between transcript levels of MtCEP1 and MtCEP2 with the number of lateral roots. MtCEP1 peptide-dependent phenotypes were abolished or attenuated by altering or deleting key residues in its 15 amino acid domain. RNA-Seq analysis revealed that 89 and 116 genes were significantly up- and down-regulated, respectively, by MtCEP1 overexpression, including transcription factors WRKY, bZIP, ERF, and MYB, homologues of LOB29, SUPERROOT2, and BABY BOOM. Taken together, the data suggest that the MtCEP1 peptide modulates lateral root and nodule development in M. truncatula.
CEP 信号肽家族成员 MtCEP1 在蒺藜苜蓿根发育中的作用。MtCEP1 在根尖、维管组织和幼侧器官中表达，并受低氮水平和独立的高 CO2 上调。过表达 MtCEP1 或向根中施加 MtCEP1 肽会引起发育表型：抑制侧根形成、增强结瘤和诱导周期性周向根肿胀，这是由皮层、表皮和周细胞分裂引起的，具有额外的皮层细胞层。MtCEP 肽添加到其他豆科植物物种中诱导了类似的表型。MtCEP1 增强结瘤对高硝酸盐部分耐受，高硝酸盐通常强烈抑制结瘤。这些根瘤在不存在和存在抑制硝酸水平的情况下生长更快、更大，并固定更多的氮。在 25mM 硝酸盐下，在 MtCEP1 过表达诱导的现有肿胀部位形成了结节。几种 MtCEP 基因的 RNA 干扰介导的沉默显示 MtCEP1 和 MtCEP2 的转录本水平与侧根数量之间存在负相关。MtCEP1 肽依赖性表型通过改变或删除其 15 个氨基酸结构域中的关键残基而被消除或减弱。RNA-Seq 分析显示，MtCEP1 过表达分别导致 89 个和 116 个基因显著上调和下调，包括转录因子 WRKY、bZIP、ERF 和 MYB，LOB29、SUPERROOT2 和 BABY BOOM 的同源物。总之，数据表明 MtCEP1 肽调节蒺藜苜蓿的侧根和根瘤发育。
