Regulation of SOS1, a plasma membrane Na+/H+ exchanger in Arabidopsis thaliana, by SOS2 and SOS3
Regulation of SOS1, a plasma membrane Na+/H+ exchanger in Arabidopsis thaliana, by SOS2 and SOS3
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DOI：
10.1073/pnas.122224699
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发表时间：
2002-06-11
影响因子：
11.1
通讯作者：
Zhu, JK
中科院分区：
文献类型：
--
作者：
Qiu, QS;Guo, Y;Zhu, JK
维持细胞质中低水平的钠离子对植物生长和发育至关重要。生物化学研究表明，Na+/H+交换器在植物细胞质膜有助于细胞内钠稳态通过运输钠离子出细胞，然而，这些交换器还没有被确定在分子水平上。遗传分析已经将盐过度敏感途径（SOS 1 -3）的组分与拟南芥的耐盐性联系起来。预测的SOS 1蛋白质序列和野生型和sosl植物中钠离子积累的比较表明，SOS 1直接参与钠离子跨质膜的运输。为了证明SOS 1的运输能力，我们研究了Na+/H+交换活性在野生型和SOS植物使用高度纯化的质膜囊泡。结果表明，质膜Na+/H+交换活性是存在于野生型植物与250 mM NaCl处理，但这种运输活动减少了80%，在类似的处理sosl植物。在体外添加活化的SOS 2蛋白（一种蛋白激酶）使盐处理野生型植物中的Na+/H+交换活性增加了2倍，相对于不添加蛋白质的运输。然而，添加活化的SOS 2对SOS 1植物中的交换活性没有任何刺激作用。虽然囊泡的sos 2和sos 3植物有减少质膜Na+/H+-交换活性，运输活动增加，除了激活的SOS 2蛋白。这些结果表明，SOS 1有助于质膜Na+/H+交换和SOS 2和SOS 3调节SOS 1运输活性。
Maintaining low levels of sodium ions in the cell cytosol is critical for plant growth and development. Biochemical studies suggest that Na+/H+ exchangers in the plasma membrane of plant cells contribute to cellular sodium homeostasis by transporting sodium ions out of the cell; however, these exchangers have not been identified at the molecular level. Genetic analysis has linked components of the salt overly sensitive pathway (SOS1-3) to salt tolerance in Arabidopsis thaliana. The predicted SOS1 protein sequence and comparisons of sodium ion accumulation in wildtype and sosl plants suggest that SOS1 is involved directly in the transport of sodium ions across the plasma membrane. To demonstrate the transport capability of SOS1, we studied Na+/H+-exchange activity in wild-type and sos plants using highly purified plasma membrane vesicles. The results showed that plasma membrane Na+/H+-exchange activity was present in wild-type plants treated with 250 mM NaCl, but this transport activity was reduced by 80% in similarly treated sosl plants. In vitro addition of activated SOS2 protein (a protein kinase) increased Na+/H+-exchange activity in salt-treated wild-type plants 2-fold relative to transport without added protein. However, the addition of activated SOS2 did not have any stimulatory effect on the exchange activity in sosl plants. Although vesicles of sos2 and sos3 plants had reduced plasma membrane Na+/H+-exchange activity, transport activity in both increased with the addition of activated SOS2 protein. These results demonstrate that SOS1 contributes to plasma membrane Na+/H+ exchange and that SOS2 and SOS3 regulate SOS1 transport activity.