Biology Department, 208 Mueller Laboratory, Penn State University, University Park, Pennsylvania 16802, USA.
J Proteome Res. 2010 Apr 5;9(4):1637-47. doi: 10.1021/pr901011h.
Signaling cascades mediated by heterotrimeric G proteins are ubiquitous and important signal transduction mechanisms in both metazoans and plants. In the model plant Arabidopsis thaliana, the sole canonical G protein alpha subunit, GPA1, has been implicated in multiple signaling events, including guard cell movement regulated by the plant stress hormone abscisic acid (ABA). However, only a handful of proteins have been demonstrated to be involved in GPA1 signaling to date. Here, we compared the proteome composition of guard cells from wild type Col vs gpa1-4 null mutants with and without ABA treatment using iTRAQ technology to identify guard cell proteins whose abundance was affected by ABA and/or GPA1. After imposition of strict selection criteria, the abundance of two proteins in Col and six proteins in gpa1-4 was found to be affected by ABA in guard cells, and 18 guard cell proteins were quantitatively affected by the mutation of GPA1. On the basis of known functions of the differentially expressed proteins, our data suggest that GPA1 inhibits guard cell photosynthesis and promotes the availability of reactive oxygen species (ROS) in guard cells. These results exemplify how iTRAQ can be used to quantitatively study single cell signaling pathways in Arabidopsis.
异三聚体 G 蛋白介导的信号级联反应在后生动物和植物中都是普遍存在且重要的信号转导机制。在模式植物拟南芥中，唯一的经典 G 蛋白α亚基 GPA1 被认为参与了多种信号事件，包括植物应激激素脱落酸（ABA）调节的保卫细胞运动。然而，迄今为止，只有少数几种蛋白质被证明参与了 GPA1 信号转导。在这里，我们使用 iTRAQ 技术比较了野生型 Col 和 gpa1-4 缺失突变体保卫细胞在有/无 ABA 处理时的蛋白质组组成，以鉴定ABA 和/或 GPA1 影响其丰度的保卫细胞蛋白。在施加严格的选择标准后，发现 Col 中有两种蛋白和 gpa1-4 中有六种蛋白的丰度受 ABA 影响，18 种保卫细胞蛋白的丰度受 GPA1 突变的定量影响。基于差异表达蛋白的已知功能，我们的数据表明 GPA1 抑制保卫细胞光合作用并促进保卫细胞中活性氧（ROS）的产生。这些结果说明了 iTRAQ 如何用于定量研究拟南芥的单细胞信号通路。
