School of Plant Sciences, University of Arizona.
School of Plant Sciences, University of Arizona
Mol Biol Evol. 2014 Aug;31(8):2094-107. doi: 10.1093/molbev/msu152. Epub 2014 May 6.
Eutrema salsugineum and Schrenkiella parvula are salt-tolerant relatives of the salt-sensitive species Arabidopsis thaliana. An important component of salt tolerance is the regulation of Na(+) ion homeostasis, which occurs in part through proteins encoded by the Cation/Proton Antiporter-1 (CPA1) gene family. We used a combination of evolutionary and functional analyses to examine the role of CPA1 genes in the salt tolerance of E. salsugineum and Sc. parvula, and found evidence that changes in CPA1-mediated Na(+) extrusion may contribute to the salt tolerance of both species. Specifically, we found that a member of the CPA1 family, the Na(+)/H(+) antiporter gene Salt Overly Sensitive 1 (SOS1), evolved under positive selection in E. salsugineum. In the absence of activation by the SOS2 kinase/SOS3 calcium-binding protein complex, SOS1 from E. salsugineum (EsSOS1) confers greater salt tolerance than SOS1 from Sc. parvula (SpSOS1) and Ar. thaliana (AtSOS1) when expressed in a salt-sensitive strain of Saccharomyces cerevisiae. A single amino acid change in the putative autoinhibitory domain is required but not sufficient for the enhanced salt tolerance conferred by EsSOS1. When activated by SOS2 and SOS3, both EsSOS1 and SpSOS1 confer greater salt tolerance than AtSOS1. Enhanced SOS1-mediated Na(+) extrusion therefore appears to contribute to the salt tolerance of both E. salsugineum and Sc. parvula, although through apparently different mechanisms.
盐地碱蓬和小盐芥是对盐敏感的拟南芥的耐盐近缘种。耐盐性的一个重要组成部分是调节钠离子稳态，这部分是通过阳离子/质子反向转运蛋白-1（CPA1）基因家族编码的蛋白质来实现的。我们使用进化和功能分析的组合来研究 CPA1 基因在盐地碱蓬和小盐芥耐盐性中的作用，发现 CPA1 介导的 Na+外排的变化可能有助于这两个物种的耐盐性的证据。具体来说，我们发现 CPA1 家族的一个成员，Na+/H+反向转运蛋白基因盐过度敏感 1（SOS1），在盐地碱蓬中经历了正选择。在没有 SOS2 激酶/SOS3 钙结合蛋白复合物激活的情况下，盐地碱蓬中的 SOS1（EsSOS1）在表达于一种对盐敏感的酿酒酵母菌株中时，比小盐芥中的 SOS1（SpSOS1）和拟南芥中的 SOS1（AtSOS1）赋予更高的耐盐性。假定的自抑制结构域中的单个氨基酸变化是必需的，但不足以赋予 EsSOS1 增强的耐盐性。当被 SOS2 和 SOS3 激活时，EsSOS1 和 SpSOS1 都比 AtSOS1 赋予更高的耐盐性。因此，增强的 SOS1 介导的 Na+外排似乎有助于盐地碱蓬和小盐芥的耐盐性，尽管通过的机制显然不同。
