玉米阳离子/质子逆向转运蛋白ZmNHX7的功能鉴定

植物阳离子/质子逆向转运蛋白可以维持细胞内的离子平衡,在抵御离子毒害过程中发挥重要作用。本研究克隆了一个编码玉米阳离子/质子逆向转运蛋白的基因,命名为ZmNHX7。该基因编码序列(codingsequence,CDS)全长3411 bp,编码一条含1136个氨基酸的多肽链。ZmNHX7基因在玉米各组织部位均有表达,在V7 (第7片叶完全展开)时期的根和茎中表达量较高。在NaCl与LiCl的胁迫条件下,该基因表达量上调。系统进化树分析将ZmNHX7与拟南芥质膜阳离子/质子逆向转运蛋白AtNHX7和AtNHX8归为一类,亚细胞定位结果表明该蛋白定位于细胞膜和核膜上。将ZmNHX7基因转入拟南芥T-DNA插入突变体中,转基因互补株系可以恢复该突变体对Li+的耐受性。这些结果表明, ZmNHX7编码一个玉米质膜阳离子/质子逆向转运蛋白,在缓解Li+对植物的毒害和维持细胞内的离子平衡等方面发挥重要作用。

Functional identification of maize cation/proton antiporter ZmNHX7

Plant cation/proton antiporters can maintain intracellular ion homeostasis and resist ion toxicity. In this study, a gene encoding a maize cation/proton antiporter was cloned and named as ZmNHX7. The coding sequence of ZmNHX7 was 3411 bp, encoding a protein with 1136 amino acids. ZmNHX7 is ubiquitously expressed in various tissues of maize, With higher expression level in roots and stems at the V7 stage. The expression of ZmNHX7 was induced by NaCl and LiCl stresses. In phylogenetic tree ZmNHX7 showed a close relation with AtNHX7 and AtNHX8 of Arabidopsis thaliana. ZmNHX7 was located in cell membrane and nuclear membrane by confocal laser scanning microscopy analysis of the lower epidermis of tobacco leaves. When ZmNHX7 gene was transformed into the Arabidopsis thaliana T-DNA insertion mutant nhx8, the transgenic complementary lines could restore the tolerance of nhx8 to Li⁺. These results indicate that ZmNHX7 encodes a plasma membrane cation/proton antiporter of maize, which plays an important role in reducing the toxicity of Li⁺ to plants and maintaining intracellular ion homeostasis.