Control of plant exocyst function by protein phosphorylation in root hairs and pollen tubes - regulation of tip growth through AGC1 kinases and exocyst phosphoregulation

通过根毛和花粉管中的蛋白质磷酸化控制植物外囊功能 - 通过 AGC1 激酶和外囊磷酸调节调节尖端生长

• 批准号: 391059800
• 负责人: Professor Dr. Claus Schwechheimer
• 金额: --
• 依托单位: Lehrstuhl für Systembiologie der Pflanzen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/391059800?language=en
• 关键词: Control; plant; exocyst; function; protein

Root hairs and pollen tubes are tip-growing cells that target cellular growth exclusively to one focal region at the cell surface. Exocyst is a conserved multiprotein complex required for the tethering of transport vesicles to the plasma membrane to sustain the secretion of membrane and cell wall material. We have characterized the three Arabidopsis protein kinases AGC1.5, AGC1.6, and AGC1.7 that are strongly expressed in root hairs and pollen tubes. Loss-of-function mutations and overexpression of the kinases lead to polarity defects in both tip growing processes, indicating that these kinases are required for proper tip growth. The kinases localize, in root hair cells, to the subapical region where they may positively or negatively regulate fusion, membrane recycling or membrane transport processes. Exo70C1 and Exo70C2, soluble subunits of exocyst, are highly abundant in both cell types and Exo70C1 is phosphorylated by the three AGC1 kinases in vitro. Here, we will test the in vivo relevance of the Exo70C1 phosphorylation by mapping phosphorylation sites in vitro, test the ability of the protein to complement mutant phenotypes and examine whether the paralogous, Exo70C2 as well as other exocyst subunits of interest are also AGC1 phosphorylation targets. Further, we will examine the role of nitrosylation in controlling AGC1.5, AGC1.6, and AGC1.7 activity, which is interesting in view of the fact that nitrosylation gradients have been described in root hair and pollen tube growth that could regulate the kinases at the subcellular level.

根毛和花粉管是顶端生长的细胞，其细胞生长仅针对细胞表面的一个焦点区域。外囊是一种保守的多蛋白复合物，需要将运输囊泡拴系到质膜上以维持膜和细胞壁物质的分泌。我们的特点是三个拟南芥蛋白激酶AGC1.5，AGC1.6和AGC1.7强烈表达在根毛和花粉管。失功能突变和过度表达的激酶导致极性缺陷的尖端生长过程中，表明这些激酶是必要的适当的尖端生长。在根毛细胞中，激酶定位于根尖下区域，在那里它们可以正向或负向调节融合、膜再循环或膜运输过程。Exo70C1和Exo70C2是外囊的可溶性亚基，在两种细胞类型中高度丰富，并且Exo70C1在体外被三种AGC1激酶磷酸化。在这里，我们将通过体外定位磷酸化位点来测试Exo70C1磷酸化的体内相关性，测试蛋白质补充突变表型的能力，并检查旁系同源物、Exo70C2以及其他感兴趣的外囊亚基是否也是AGC1磷酸化靶点。此外，我们将研究亚硝基化在控制AGC1.5，AGC1.6，和AGC1.7活性，这是有趣的事实，亚硝基化梯度已被描述在根毛和花粉管生长，可以调节激酶在亚细胞水平上的作用。