CO2 regulator SLAC1 and its homologues are essential for anion homeostasis in plant cells
CO2 regulator SLAC1 and its homologues are essential for anion homeostasis in plant cells
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DOI：
10.1038/nature06720
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发表时间：
2008-03-27
期刊：
影响因子：
64.8
通讯作者：
Iba, Koh
中科院分区：
文献类型：
--
作者：
Negi, Juntaro;Matsuda, Osamu;Iba, Koh
预计大气[ CO2]的持续上升将对农业生产力、植物生态系统和气体交换产生各种各样的巨大影响（1-3）。表皮中的气孔为植物和大气之间的CO2和水交换提供了大门，这是对植物生命至关重要的过程（4-6）。增加[ CO2]已被证明可以增强阴离子通道活性（7），该活性被认为可以在气孔关闭期间介导气孔调节阴离子（Cl-和苹果酸（2-））从保卫细胞流出（8，9）。然而，编码植物质膜阴离子外排通道的基因仍然未知。在这里，我们报告的分离拟南芥基因，SLAC 1（慢阴离子通道相关1，At 1g 12480），它介导的CO2敏感性调节植物气体交换。SLAC 1蛋白是细菌和真菌C4-二羧酸转运蛋白的远端同源物，并且特异性地定位于保卫细胞的质膜。它属于一个蛋白质家族，在拟南芥中由四个结构相关的成员组成，这些成员在质膜定位中是常见的，但显示出不同的组织特异性表达模式。SLAC 1的功能丧失突变伴随着保卫细胞原生质体中阴离子的过度积累。SLAC 1或其家族成员的保卫细胞特异性表达导致野生型气孔反应的恢复，包括CO2敏感性，并且还导致过度积累的阴离子的消散。这些结果表明，SLAC 1家族蛋白具有进化上保守的功能，这是维持细胞水平上的有机/无机阴离子稳态所必需的。
The continuing rise in atmospheric [ CO2] is predicted to have diverse and dramatic effects on the productivity of agriculture, plant ecosystems and gas exchange(1-3). Stomatal pores in the epidermis provide gates for the exchange of CO2 and water between plants and the atmosphere, processes vital to plant life(4-6). Increased [ CO2] has been shown to enhance anion channel activity(7) proposed to mediate efflux of osmoregulatory anions ( Cl- and malate(2-)) from guard cells during stomatal closure(8,9). However, the genes encoding anion efflux channels in plant plasma membranes remain unknown. Here we report the isolation of an Arabidopsis gene, SLAC1 ( SLOW ANION CHANNEL-ASSOCIATED 1, At1g12480), which mediates CO2 sensitivity in regulation of plant gas exchange. The SLAC1 protein is a distant homologue of bacterial and fungal C4- dicarboxylate transporters, and is localized specifically to the plasma membrane of guard cells. It belongs to a protein family that in Arabidopsis consists of four structurally related members that are common in their plasma membrane localization, but show distinct tissue- specific expression patterns. The loss- of- function mutation in SLAC1 was accompanied by an over- accumulation of the osmoregulatory anions in guard cell protoplasts. Guard- cell- specific expression of SLAC1 or its family members resulted in restoration of the wild- type stomatal responses, including CO2 sensitivity, and also in the dissipation of the over- accumulated anions. These results suggest that SLAC1-family proteins have an evolutionarily conserved function that is required for the maintenance of organic/ inorganic anion homeostasis on the cellular level.