紫花苜蓿Na^＋/H^＋逆向转运蛋白基因在拟南芥中表达提高转基因植株的耐盐性

Expression of a Vacuolar Na^+/H^+ Antiporter Gene of Alfalfa Enhances Salinity Tolerance in Transgenic Arabidopsis

以紫花苜蓿(Medicago sativa)为材料,利用反转录PCR方法分离了NHX1全长cDNA(命名为MsNHX1)。Southern杂交结果表明,在紫花苜蓿中存在一个小的液泡型Na+/H+逆向转运蛋白基因家族。序列分析表明,该基因所编码的蛋白与拟南芥、水稻和棉花中液泡型Na+/H+逆向转运蛋白具有较高的同源性。在洋葱表皮细胞中瞬时表达MsNHX1-GFP融合基因的结果表明,MsNHX1定位在液泡膜上。Northern杂交发现该基因的表达受高浓度NaCl诱导。MsNHX1在盐敏感酵母突变体中表达可以提高转化子对NaCl的耐受性,说明MsNHX1具有转运Na+的功能。在拟南芥中表达MsNHX1能显著提高植株耐受盐胁迫的能力;而且在受到盐胁迫时,转基因植株比野生型的渗透调节能力更强,生物膜受破坏程度降低,光合能力增强。以上研究结果表明MsNHX1是一个液泡膜Na+/H+逆向转运蛋白,在植物耐受盐胁迫过程中起重要作用。

Plant Na^＋/H^＋ antiporters play an important role in salt tolerance. An alfalfa （Medicago sativa） full length cDNA （named as MsNHX1） was isolated by RT-PCR according to the homologous region of plant Na^＋/H^＋ antiporter genes. Southern blot analysis revealed that there was a small antiporter gene family in alfalfa genome. Sequence analysis indicated that MsNHX1 shared high homology with other vacuolar Na^＋/H^＋ antiporters. Transient transfection of MsNHX1-GFP fusion gene revealed that MsNHX1 targeted to vacuolar membrane. The transcription of MsNHX1 was up-regulated after high salinity treatment. Furthermore, the expression of MsNHX1 in yeast partly suppressed the salt-sensitive phenotype of yeast Na^＋/H^＋ antiporter mutant, indicating that MsNHX1 was a functional Na^＋/H^＋ antiporter of alfalfa. The physiological analysis revealed that the expression of MsNHX1 in Arabidopsis enhanced the resistance of transgenic plants to salt stress. These results suggest that MsNHX1 is a vacuolar Na^＋/H^＋ antiporter and functions in salt tolerance of plants.