Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, Japan.
Planta. 2011 Jan;233(1):175-88. doi: 10.1007/s00425-010-1289-4. Epub 2010 Oct 21.
We previously cloned a vacuolar Na+/H+ antiporter gene (OsNHX1) from rice (Oryza sativa). Here we identified four additional NHX-type antiporter genes in rice (OsNHX2 through OsNHX5) and performed molecular and functional analyses of those genes. The exon-intron structure of the OsNHX genes and the phylogenetic tree of the OsNHX proteins suggest that the OsNHX proteins are categorized into two subgroups (OsNHX1 through OsNHX4 and OsNHX5). OsNHX1, OsNHX2, OsNHX3, and OsNHX5 can suppress the Na+, Li+, and hygromycin sensitivity of yeast nhx1 mutants and their sensitivity to a high K+ concentration. The expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 is regulated differently in rice tissues and is increased by salt stress, hyperosmotic stress, and ABA. When we studied the expression of β-glucuronidase (GUS) driven by either the OsNHX1 or the OsNHX5 promoter, we observed activity in the stele, the emerging part of lateral roots, the vascular bundle, the water pore, and the basal part of seedling shoots with both promoters. In addition, each promoter had a unique expression pattern. OsNHX1 promoter-GUS activity only was localized to the guard cells and trichome, whereas OsNHX5 promoter-GUS activity only was localized to the root tip and pollen grains. Our results suggest that the members of this gene family play important roles in the compartmentalization into vacuoles of the Na+ and K+ that accumulate in the cytoplasm and that the differential regulation of antiporter gene expression in different rice tissues may be an important factor determining salt tolerance in rice.
我们之前从水稻中克隆了液泡 Na+/H+反向转运蛋白基因（OsNHX1）。在这里，我们鉴定了水稻中另外 4 个 NHX 型反向转运蛋白基因（OsNHX2 到 OsNHX5），并对这些基因进行了分子和功能分析。OsNHX 基因的外显子-内含子结构和 OsNHX 蛋白的系统发育树表明，OsNHX 蛋白分为两个亚组（OsNHX1 到 OsNHX4 和 OsNHX5）。OsNHX1、OsNHX2、OsNHX3 和 OsNHX5 可以抑制酵母 nhx1 突变体的 Na+、Li+和 Hygromycin 敏感性及其对高 K+浓度的敏感性。OsNHX1、OsNHX2、OsNHX3 和 OsNHX5 在水稻组织中的表达受到不同的调控，并受到盐胁迫、高渗胁迫和 ABA 的诱导。当我们研究由 OsNHX1 或 OsNHX5 启动子驱动的β-葡萄糖醛酸酶（GUS）的表达时，我们观察到在茎、侧根的分生组织、维管束、水孔和幼苗茎的基部都有活性，两个启动子都有活性。此外，每个启动子都有独特的表达模式。OsNHX1 启动子-GUS 活性仅定位于保卫细胞和毛状体，而 OsNHX5 启动子-GUS 活性仅定位于根尖和花粉粒。我们的结果表明，该基因家族的成员在将细胞质中积累的 Na+和 K+区室化到液泡中起着重要作用，而不同水稻组织中反向转运蛋白基因表达的差异调控可能是决定水稻耐盐性的一个重要因素。
