Na^+/H^+逆向转运蛋白基因在甜瓜不同品种中的表达

Expression of Na^+/H^+ Antiporter Gene in Salt-Sensitive and Salt-Tolerant Melon Varieties

Na+/H+逆向运输蛋白基因在植物耐盐性方面起着极为重要的作用。根据同源基因保守序列设计引物,通过RACE方法从甜瓜中克隆了Na+/H+逆向转运蛋白基因,命名为CmNHX1(FJ843078)。序列分析表明,该基因全长2 534bp,开放读码框为1 659bp,编码553个氨基酸多肽。氨基酸同源性分析表明该蛋白与液泡型Na+/H+逆向转运蛋白的亲缘关系较近,与质膜型Na+/H+逆向转运蛋白的亲缘关系较远。RT-PCR表达分析结果表明,CmNHX1在甜瓜根茎叶中均有表达,而且随着NaCl浓度和处理时间的增加,在根中表达持续增强,叶片中表达持续下降。耐盐品种‘金辉’根、茎和叶中的CmNHX1表达均高于盐敏感品种‘天仙’根、茎和叶中的表达。有趣的是在根中的表达,CmNHX1相对表达量在‘金辉’中是‘天仙’的2倍。CmNHX1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CmNHX1具有转运Na+的功能。研究结果表明CmNHX1是一个液泡膜Na+/H+逆向转运蛋白,在甜瓜盐胁迫过程中起着重要作用。

Na＋/H＋ antiporters play an important role in salt tolerance of plant.A melon（Cucumis melo L.） full length cDNA（named as CmNHX1） was isolated by RACE approach according to the homologous region of plant Na＋/H＋ antiporter genes.Sequence analysis indicated that the full-length cDNA of CmNHX1 was 2 534 bp,including an open reading frame（ORF） of 1 659 bp,which encoded a deduced polypeptide of 553 amino acids.The deduced protein contained antiporters from other higher plants.As shown by RT-PCR,expression of CmNHX1 is detectable in roots,stems and leaves.In addition,the expression increases in root but decreases in leaves with increasing NaCl concentration.Similarly,expression increased with increasing time in plants treated with 100 mmol/L NaCl.Expression of CmNHX1 is higher in Jinhui＇s root,shoot and leaf tissues than that of in Tianxian.Expression of CmNHX1 in ATX3 yeast Na＋/H＋ antiporter mutants show functional complementation.These results indicated that the CmNHX1 protein play an important in Cucumis melo L.in salty conditions.