Functional analysis of CHX21:: a putative sodium transporter in Arabidopsis
Functional analysis of CHX21:: a putative sodium transporter in Arabidopsis
复制标题
DOI：
10.1093/jxb/erj092
复制
发表时间：
2006-03-01
影响因子：
6.9
通讯作者：
Pritchard, J
中科院分区：
文献类型：
--
作者：
Hall, D;Evans, AR;Pritchard, J
CHX21 是拟南芥 CHX 阳离子转运蛋白家族的成员，其功能作用已在“理想”条件下和氯化钠水平升高的情况下生长的植物中进行了研究。在公共数据库中，AtCHX21 (At2g31910) 被注释为假定的 Na+/H+ 反向转运蛋白。在这项研究中，Southern 分析用于鉴定其基因组中包含单个转座子插入的基因型；使用 PCR，该插入被证明位于 CHX21 基因座内。使用 RT-PCR 在 Atchx21（突变体）植物中未检测到 CHX21 转录本。在没有盐胁迫的情况下，Atchx21在莲座宽度和开花时间等性状的发育过程中与野生型（AtCHX21）表现出显着的数量差异。在 50 mM NaCl 存在下，(i) Atchx21 的根伸长速度比野生型更慢，(ii) Atchx21 叶液 Na+ 浓度显着低于野生型，(iii) 木质部 Na+ 浓度低于野生型。韧皮部中叶子输出的Na+浓度没有变化。因此，根木质部中 Na+ 的负载可以解释 Na+ 叶片浓度的变化。这一假设得到了免疫定位的支持，免疫定位证明 AtCHX21 转运蛋白只能在根内胚层细胞中检测到。超薄切片的免疫金标记，随后进行透射电子显微镜，证明了蛋白质在质膜中的定位。数据表明，CHX21 转运蛋白可能在木质部 Na+ 浓度的调节中发挥作用，从而调节叶片中 Na+ 的积累。
The functional role of CHX21, a member of the Arabidopsis thaliana CHX cation transporter family, has been investigated in plants growing under 'ideal' conditions and in the presence of elevated NaCl levels. In public databases, AtCHX21 (At2g31910) is annotated as a putative Na+/H+ antiporter. In this study, Southern analysis was used to identify a genotype that contained a single transposon insertion within its genome; using PCR, this insertion was shown to be within the CHX21 locus. No CHX21 transcript was detectable in Atchx21 (mutant) plants using RT-PCR. In the absence of salt stress, Atchx21 showed significant quantitative differences from the wild type (AtCHX21) in development with respect to characters such as rosette width and flowering time. In the presence of 50 mM NaCl, (i) roots of Atchx21 elongated more slowly than the wild type, (ii) the leaf sap Na+ concentration was significantly lower in Atchx21 compared with the wild type, and (iii) the concentration of Na+ in the xylem was lower compared with the wild type. The concentration of Na+ exported from the leaf in the phloem was unchanged. Thus, loading of Na+ into the root xylem could explain changes in leaf concentration of Na+. This hypothesis was supported by immunolocalization which demonstrated that the AtCHX21 transporter could only be detected in root endodermal cells. Immunogold labelling of ultra-thin sections, followed by transmission electron microscopy, demonstrated the localization of the protein in the plasma membrane. The data demonstrate that the CHX21 transporter may play a role in regulation of xylem Na+ concentration and, consequently, Na+ accumulation in the leaf.