Functional analysis of AtHKT1 in Arabidopsis shows that Na+ recirculation by the phloem is crucial for salt tolerance
Functional analysis of AtHKT1 in Arabidopsis shows that Na+ recirculation by the phloem is crucial for salt tolerance
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DOI：
10.1093/emboj/cdg207
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发表时间：
2003-05-01
期刊：
影响因子：
11.4
通讯作者：
Casse, F
中科院分区：
文献类型：
--
作者：
Berthomieu, P;Conéjéro, G;Casse, F
拟南芥的两个等位基因隐性突变体sas 2 -1和sas 2 -2被鉴定为诱导茎中钠的过度积累。发现sas 2基因座（通过定位克隆）对应于AtHKT 1基因。在非洲爪蟾卵母细胞中的表达表明，sas 2 -1突变不影响转运蛋白的离子选择性，但强烈降低了宏观（整个卵母细胞电流）的运输活动。在拟南芥中，AtHKT 1的表达被证明仅限于所有器官的韧皮部组织。sas 2 -1突变强烈降低韧皮部汁液中的Na+浓度。除茎外，地上部各器官均出现Na+过量积累，而根中Na+积累不足。sas 2植株对NaCl的敏感性增强，在中等盐度下生长减缓甚至死亡。整个数据集表明，AtHKT 1参与Na+从芽到根的再循环，可能是通过介导Na+加载到韧皮部汁液在芽和卸载在根中，这种再循环去除大量的Na+从芽和植物耐盐性中起着至关重要的作用。
Two allelic recessive mutations of Arabidopsis, sas2-1 and sas2-2, were identified as inducing sodium over accumulation in shoots. The sas2 locus was found (by positional cloning) to correspond to the AtHKT1 gene. Expression in Xenopus oocytes revealed that the sas2-1 mutation did not affect the ionic selectivity of the transporter but strongly reduced the macro scopic (whole oocyte current) transport activity. In Arabidopsis, expression of AtHKT1 was shown to be restricted to the phloem tissues in all organs. The sas2-1 mutation strongly decreased Na+ concentration in the phloem sap. It led to Na+ overaccumulation in every aerial organ (except the stem), but to Na+ underaccumulation in roots. The sas2 plants displayed increased sensitivity to NaCl, with reduced growth and even death under moderate salinity. The whole set of data indicates that AtHKT1 is involved in Na+ recirculation from shoots to roots, probably by mediating Na+ loading into the phloem sap in shoots and unloading in roots, this recirculation removing large amounts of Na+ from the shoot and playing a crucial role in plant tolerance to salt.