Root-to-shoot transport of sulfate in Arabidopsis. Evidence for the role of SULTR3;5 as a component of low-affinity sulfate transport system in the root vasculature
Root-to-shoot transport of sulfate in Arabidopsis. Evidence for the role of SULTR3;5 as a component of low-affinity sulfate transport system in the root vasculature
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DOI：
10.1104/pp.104.045625
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发表时间：
2004-12-01
期刊：
影响因子：
7.4
通讯作者：
Takahashi, H
中科院分区：
文献类型：
--
作者：
Kataoka, T;Hayashi, N;Takahashi, H
木质部运输硫酸盐调节维管植物中硫的分配。在这里，我们描述SULTR 3; 5作为硫酸盐运输系统的重要组成部分，促进了硫酸盐在脉管系统中从根到茎的运输。在拟南芥（Arabidopsis thaliana）中，SULTR 3;5与SULTR 2;1低亲和力硫酸盐转运蛋白共定位于根的木质部薄壁组织和周壁细胞中。在酵母（酿酒酵母）表达系统中，仅用SULTR 3;5表达几乎检测不到硫酸盐摄取;然而，共表达SULTR 3;5和SULTR 2;1的细胞显示出显著高于仅用SULTR 2;1表达的显著摄取活性。与SULTR 3;5-SULTR 2;1共表达的硫酸盐摄取活性的V-max值比单独的SULTR 2;1高约3倍。在拟南芥中，根到地上部运输的硫酸盐受到限制，在sultr 3;5突变体，在硫限制后的根中的高SULTR 2;1表达的条件下。这些结果表明，SULTR 3;5是组成型表达在根维管系统，但其功能，以加强SULTR 2;1双亲和转运蛋白的能力是必不可少的，只有当SULTR 2;1 mRNA诱导硫限制。因此，SULTR 3;5和SULTR 2;1的共表达提供了最大能力的硫酸盐运输活性，这有利于检索质外体硫酸盐的木质部薄壁细胞中的脉管系统的拟南芥根，并可能有助于根到地上运输的硫酸盐。
Xylem transport of sulfate regulates distribution of sulfur in vascular plants. Here, we describe SULTR3;5 as an essential component of the sulfate transport system that facilitates the root-to-shoot transport of sulfate in the vasculature. In Arabidopsis (Arabidopsis thaliana), SULTR3;5 was colocalized with the SULTR2;1 low-affinity sulfate transporter in xylem parenchyma and pericycle cells in roots. In a yeast (Saccharomyces cerevisiae) expression system, sulfate uptake was hardly detectable with SULTR3;5 expression alone; however, cells coexpressing both SULTR3;5 and SULTR2;1 showed substantial uptake activity that was considerably higher than with SULTR2;1 expression alone. The V-max value of sulfate uptake activity with SULTR3;5-SULTR2;1 coexpression was approximately 3 times higher than with SULTR2;1 alone. In Arabidopsis, the root-to-shoot transport of sulfate was restricted in the sultr3;5 mutants, under conditions of high SULTR2;1 expression in the roots after sulfur limitation. These results suggested that SULTR3;5 is constitutively expressed in the root vasculature, but its function to reinforce the capacity of the SULTR2;1 tow-affinity transporter is only essential when SULTR2;1 mRNA is induced by sulfur limitation. Consequently, coexpression of SULTR3;5 and SULTR2;1 provides maximum capacity of sulfate transport activity, which facilitates retrieval of apoplastic sulfate to the xylem parenchyma cells in the vasculature of Arabidopsis roots and may contribute to the root-to-shoot transport of sulfate.