From the Laboratório de Bioquímica de Proteínas, Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz, ESALQ, Universidade de São Paulo, USP, Piracicaba, SP, 13418-900 and.
the Laboratório de Biologia Molecular de Plantas, Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, ESALQ, Universidade de São Paulo, USP, Piracicaba, SP, 13418-900, Brazil.
J Biol Chem. 2018 Feb 9;293(6):2159-2171. doi: 10.1074/jbc.M117.808881. Epub 2017 Dec 27.
rapid alkalinization factor 1 (AtRALF1) is a small secreted peptide hormone that inhibits root growth by repressing cell expansion. Although it is known that AtRALF1 binds the plasma membrane receptor FERONIA and conveys its signals via phosphorylation, the AtRALF1 signaling pathway is largely unknown. Here, using a yeast two-hybrid system to search for AtRALF1-interacting proteins in , we identified calmodulin-like protein 38 (CML38) as an AtRALF1-interacting partner. We also found that CML38 and AtRALF1 are both secreted proteins that physically interact in a Ca- and pH-dependent manner. CML38-knockout mutants generated via T-DNA insertion were insensitive to AtRALF1, and simultaneous treatment with both AtRALF1 and CML38 proteins restored sensitivity in these mutants. Hybrid plants lacking CML38 and having high accumulation of the AtRALF1 peptide did not exhibit the characteristic short-root phenotype caused by overexpression. Although CML38 was essential for AtRALF1-mediated root inhibition, it appeared not to have an effect on the AtRALF1-induced alkalinization response. Moreover, acridinium-labeling of AtRALF1 indicated that the binding of AtRALF1 to intact roots is CML38-dependent. In summary, we describe a new component of the AtRALF1 response pathway. The new component is a calmodulin-like protein that binds AtRALF1, is essential for root growth inhibition, and has no role in AtRALF1 alkalinization.
快速碱化因子 1（AtRALF1）是一种小分泌肽激素，通过抑制细胞扩张来抑制根生长。虽然已知 AtRALF1 结合质膜受体 FERONIA 并通过磷酸化传递其信号，但 AtRALF1 信号通路在很大程度上尚不清楚。在这里，我们使用酵母双杂交系统在 中搜索 AtRALF1 相互作用蛋白，鉴定钙调蛋白样蛋白 38（CML38）为 AtRALF1 相互作用伙伴。我们还发现 CML38 和 AtRALF1 都是分泌蛋白，它们以 Ca2+和 pH 依赖性方式物理相互作用。通过 T-DNA 插入产生的 CML38 敲除突变体对 AtRALF1 不敏感，同时用 AtRALF1 和 CML38 蛋白处理可恢复这些突变体的敏感性。缺乏 CML38 且 AtRALF1 肽积累高的杂种植物没有表现出由 过表达引起的短根表型。虽然 CML38 对于 AtRALF1 介导的根抑制是必需的，但它似乎对 AtRALF1 诱导的碱化反应没有影响。此外，吖啶标记的 AtRALF1 表明 AtRALF1 与完整根的结合依赖于 CML38。总之，我们描述了 AtRALF1 反应途径的一个新组成部分。该新组件是一种钙调蛋白样蛋白，它与 AtRALF1 结合，对于根生长抑制是必需的，并且在 AtRALF1 碱化中没有作用。
