Stimulation of Nonselective Amino Acid Export by Glutamine Dumper Proteins
Stimulation of Nonselective Amino Acid Export by Glutamine Dumper Proteins
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DOI：
10.1104/pp.109.151746
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发表时间：
2010-02-01
期刊：
影响因子：
7.4
通讯作者：
Pilot, Guillaume
中科院分区：
文献类型：
--
作者：
Pratelli, Rejane;Voll, Lars M.;Pilot, Guillaume
氨基酸在韧皮部和木质部的运输包括两个步骤：从一种细胞类型输出到质外质，然后输入到相邻的细胞。高亲和力的进口介导的质子/氨基酸共转运蛋白，而出口的机制尚不清楚。植物特异性I型膜蛋白Glutamine Dumper 1（GDU 1）的增强表达先前已显示诱导来自根状体的谷氨酰胺的分泌并增加叶质外体和木质部汁液中的氨基酸含量。在这项工作中，耐受低浓度的氨基酸和运输分析，使用放射性标记的氨基酸表明，净氨基酸摄取减少谷氨酰胺分泌GDU 1过表达gdu 1 -1D。苯丙氨酸的净摄取率随着时间的推移而下降，与野生型相比，gdu 1 -1D中的氨基酸净流出增加，表明细胞中的氨基酸输出增加。从质子梯度和ATP的出口的独立性表明，GDU 1的过度表达影响一个被动的出口系统。七个拟南芥（Arabidopsis thaliana）GDU基因中的每一个都导致了相似的表型，包括增加了广谱氨基酸的外排。表达谱和功能特性的差异表明，GDU基因在根，脉管系统和生殖器官中发挥不同的作用。两者合计，GDU似乎通过激活非选择性氨基酸促进剂来刺激氨基酸输出。
Phloem and xylem transport of amino acids involves two steps: export from one cell type to the apoplasm, and subsequent import into adjacent cells. High-affinity import is mediated by proton/amino acid cotransporters, while the mechanism of export remains unclear. Enhanced expression of the plant-specific type I membrane protein Glutamine Dumper1 (GDU1) has previously been shown to induce the secretion of glutamine from hydathodes and increased amino acid content in leaf apoplasm and xylem sap. In this work, tolerance to low concentrations of amino acids and transport analyses using radiolabeled amino acids demonstrate that net amino acid uptake is reduced in the glutamine-secreting GDU1 overexpressor gdu1-1D. The net uptake rate of phenylalanine decreased over time, and amino acid net efflux was increased in gdu1-1D compared with the wild type, indicating increased amino acid export from cells. Independence of the export from proton gradients and ATP suggests that overexpression of GDU1 affects a passive export system. Each of the seven Arabidopsis (Arabidopsis thaliana) GDU genes led to similar phenotypes, including increased efflux of a wide spectrum of amino acids. Differences in expression profiles and functional properties suggested that the GDU genes fulfill different roles in roots, vasculature, and reproductive organs. Taken together, the GDUs appear to stimulate amino acid export by activating nonselective amino acid facilitators.