Department of Biology, College of Sciences, Sultan Qaboos University, P.O. Box 36, 123, Muscat, Oman.
Department of Crop Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, 123, Muscat, Oman.
Plant Cell Rep. 2020 Aug;39(8):1079-1093. doi: 10.1007/s00299-020-02549-5. Epub 2020 May 7.
A sodium hydrogen exchanger (NHX) gene from the date palm enhances tolerance to salinity in Arabidopsis plants. Plant sodium hydrogen exchangers/antiporters (NHXs) are pivotal regulators of intracellular Na/K and pH homeostasis, which is essential for salt stress adaptation. In this study, a novel orthologue of Na/H antiporter was isolated from date palm (PdNHX6) and functionally characterized in mutant yeast cells and Arabidopsis plants to assess the behavior of the transgenic organisms in response to salinity. Genetically transformed yeast cells with PdNHX6 were sensitive to salt stress when compared to the empty vector (EV) yeast cells. Besides, the acidity value of the vacuoles of the transformant yeast cells has significantly (p ≤ 0.05) increased, as indicated by the calibrated fluorescence intensity measurements and the fluorescence imagining analyses. This observation supports the notion that PdNHX6 might regulate proton pumping into the vacuole, a crucial salt tolerance mechanism in the plants. Consistently, the transient overexpression and subcellular localization revealed the accumulation of PdNHX6 in the tonoplast surrounding the central vacuole of Nicotiana benthamiana leaf epidermal cells. Stable overexpression of PdNHX6 in Arabidopsis plants enhanced tolerance to salt stress and retained significantly higher chlorophyll, water contents, and increased seed germination under salinity when compared to the wild-type plants. Despite the significant increase of Na, transgenic Arabidopsis lines maintained a balanced Na/K ratio under salt stress conditions. Together, the results obtained from this study imply that PdNHX6 is involved in the salt tolerance mechanism in plants by controlling K and pH homeostasis of the vacuoles.
从海枣中分离出的钠离子-氢交换体（NHX）基因增强了拟南芥对盐胁迫的耐受性。植物钠离子-氢交换体/反向转运蛋白（NHXs）是细胞内 Na+/K+和 pH 稳态的关键调节剂，这对盐胁迫适应至关重要。在这项研究中，从海枣中分离出一种新型的 Na+/H+反向转运蛋白同源物（PdNHX6），并在酵母突变体和拟南芥植物中对其功能进行了表征，以评估转基因生物对盐胁迫的反应。与空载体（EV）酵母细胞相比，具有 PdNHX6 的遗传转化酵母细胞对盐胁迫敏感。此外，通过校准荧光强度测量和荧光成像分析表明，转化酵母细胞的液泡酸度值显著（p≤0.05）增加。这一观察结果支持了 PdNHX6 可能调节质子泵入液泡的观点，这是植物中重要的耐盐机制。一致地，瞬时过表达和亚细胞定位显示 PdNHX6 在烟草叶表皮细胞中央液泡周围的质膜上积累。与野生型植物相比，PdNHX6 在拟南芥植物中的稳定过表达增强了对盐胁迫的耐受性，并显著保留了更高的叶绿素、水分含量和增加的种子发芽率。尽管 Na 的含量显著增加，但转基因拟南芥系在盐胁迫条件下维持了 Na+/K+的平衡。总的来说，这项研究的结果表明，PdNHX6 通过控制液泡的 K+和 pH 稳态参与植物的耐盐机制。
