Maize ZmALMT2 is a root anion transporter that mediates constitutive root malate efflux
Maize ZmALMT2 is a root anion transporter that mediates constitutive root malate efflux
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DOI：
10.1111/j.1365-3040.2011.02479.x
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发表时间：
2012-07-01
影响因子：
7.3
通讯作者：
Pineros, Miguel
中科院分区：
文献类型：
--
作者：
Ligaba, Ayalew;Maron, Lyza;Pineros, Miguel
根外排有机酸是酸性土壤上植物耐铝的主要机制之一。这种外排是由铝激活的苹果酸转运蛋白（ALMT）或多药和毒素外排（MATE）家族的转运蛋白介导的。ZmALMT 2基因与玉米耐铝性相关。在当前的研究中，我们通过在非洲爪蟾卵母细胞和转基因拟南芥中异源表达ZmALMT 2来对其进行功能表征。在卵母细胞中，ZmALMT 2介导了有机和无机阴离子流出的铝非依赖性产电运输产物。ZmALMT 2在缺乏耐铝基因AtALMT 1和AtMATE的铝敏感拟南芥KO/KD系中的异位过表达导致了铝非依赖性组成型根苹果酸流出，这部分恢复了铝耐受表型。ZmALMT 2表达和Al耐受性之间缺乏相关性（例如，表达不定位于根尖，不被Al上调，并且在敏感玉米系中高于耐受性玉米系）也使我们质疑ZmALMT 2在Al耐受性中的作用。这里提出的ZmALMT 2转运蛋白的功能特性，沿着基因表达数据，表明ZmALMT 2不参与玉米耐铝，而是，可能发挥作用，在矿质营养的获取和运输。
Root efflux of organic acid anions underlies a major mechanism of plant aluminium (Al) tolerance on acid soils. This efflux is mediated by transporters of the Al-activated malate transporter (ALMT) or the multi-drug and toxin extrusion (MATE) families. ZmALMT2 was previously suggested to be involved in Al tolerance based on joint association-linkage mapping for maize Al tolerance. In the current study, we functionally characterized ZmALMT2 by heterologously expressing it in Xenopus laevis oocytes and transgenic Arabidopsis. In oocytes, ZmALMT2 mediated an Al-independent electrogenic transport product of organic and inorganic anion efflux. Ectopic overexpression of ZmALMT2 in an Al-hypersensitive Arabidopsis KO/KD line lacking the Al tolerance genes, AtALMT1 and AtMATE, resulted in Al-independent constitutive root malate efflux which partially restored the Al tolerance phenotype. The lack of correlation between ZmALMT2 expression and Al tolerance (e.g., expression not localized to the root tip, not up-regulated by Al, and higher in sensitive versus tolerance maize lines) also led us to question ZmALMT2's role in Al tolerance. The functional properties of the ZmALMT2 transporter presented here, along with the gene expression data, suggest that ZmALMT2 is not involved in maize Al tolerance but, rather, may play a role in mineral nutrient acquisition and transport.