Tonoplast intrinsic proteins AtTIP2;1 and AtTIP2;3 facilitate NH3 transport into the vacuole
Tonoplast intrinsic proteins AtTIP2;1 and AtTIP2;3 facilitate NH3 transport into the vacuole
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DOI：
10.1104/pp.104.051268
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发表时间：
2005-02-01
期刊：
影响因子：
7.4
通讯作者：
von Wirén, N
中科院分区：
文献类型：
--
作者：
Loqué, D;Ludewig, U;von Wirén, N
虽然膜转运蛋白介导的跨质膜铵吸收已在分子水平上得到很好的描述，鲜为人知的是分区和细胞输出的铵。(The术语铵用于表示NH3和NH 4+，并且当需要特异性时使用化学符号。）因此，我们开发了一种酵母（酿酒酵母）互补的方法，并分离出两个拟南芥（拟南芥）基因，赋予耐受性的有毒铵类似物甲基铵在酵母中。两个基因AtTIP 2; 1和AtTIP 2; AtTIP 2;1在非洲爪蟾卵母细胞中的表达随着pH的升高而增加C-14-甲基铵的积累，AtTIP 2;1-和AtTIP 2; 3-介导的酵母中的甲基铵解毒依赖于功能性液泡，这与绿色荧光蛋白-融合蛋白在植物液泡膜上的亚细胞定位一致。转录水平的两个AtTlPs氮供应的影响，但没有遵循那些氮去阻遏铵转运基因AtAMT 1;1。过表达AtTIP 2;1的转基因拟南芥植物没有表现出改变铵供应后，在根中的铵积累，虽然AtTIP 2;1在野生型植物的mRNA水平在这些条件下上调。这项研究表明，AtTIP 2;1和AtTIP 2;3可以介导甲基-NH 2和NH3跨液泡膜的胞外运输，因此可能参与液泡铵区室化。
While membrane transporters mediating ammonium uptake across the plasma membrane have been well described at the molecular level, little is known about compartmentation and cellular export of ammonium. (The term ammonium is used to denote both NH3 and NH4+ and chemical symbols are used when specificity is required.) We therefore developed a yeast (Saccharomyces cerevisiae) complementation approach and isolated two Arabidopsis (Arabidopsis thaliana) genes that conferred tolerance to the toxic ammonium analog methylammonium in yeast. Both genes, AtTIP2;1 and AtTIP2;3, encode aquaporins of the tonoplast intrinsic protein subfamily and transported methylammonium or ammonium in yeast preferentially at high medium PH. AtTIP2;1 expression in Xenopus oocytes increased C-14-methylammonium accumulation with increasing pH. AtTIP2;1- and AtTIP2;3-mediated methylammonium detoxification in yeast depended on a functional vacuole, which was in agreement with the subcellular localization of green fluorescent protein-fusion proteins on the tonoplast in planta. Transcript levels of both AtTlPs were influenced by nitrogen supply but did not follow those of the nitrogen-derepressed ammonium transporter gene AtAMT1;1. Transgenic Arabidopsis plants overexpressing AtTIP2;1 did not show altered ammonium accumulation in roots after ammonium supply, although AtTIP2;1 mRNA levels in wild-type plants were up-regulated under these conditions. This study shows that AtTIP2;1 and AtTIP2;3 can mediate the extracytosolic transport of methyl-NH2 and NH3 across the tonoplast membrane and may thus participate in vacuolar ammonium compartmentation.