Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan.
Plant Physiol. 2010 Aug;153(4):1669-77. doi: 10.1104/pp.110.155028. Epub 2010 May 24.
ATP-binding cassette (ABC) transporters represent a large family in plants, but the functions of most of these transporters are unknown. Here we report a gene, AtSTAR1, only encoding an ATP-binding domain of a bacterial-type ABC transporter in Arabidopsis (Arabidopsis thaliana). AtSTAR1 is an ortholog of rice (Oryza sativa) OsSTAR1, which has been implicated in aluminum (Al) tolerance. Knockout of AtSTAR1 resulted in increased sensitivity to Al and earlier flowering. Unlike OsSTAR1, AtSTAR1 was expressed in both the roots and shoots and its expression was not induced by Al or other stresses. Investigation of tissue-specific localization of AtSTAR1 through beta-glucuronidase fusion revealed that AtSTAR1 was predominantly expressed at outer cell layers of root tips and developing leaves, whose localization is also different from those of OsSTAR1. However, introduction of OsSTAR1 into atstar1 mutant rescued the sensitivity of atstar1 to Al, indicating that AtSTAR1 has a similar function as OsSTAR1. Furthermore, we found that AtSTAR1 may interact with ALS3, a transmembrane-binding domain in Arabidopsis to form a complex because introduction of OsSTAR1, a functional substitute of AtSTAR1, into als3 mutant resulted in the loss of OsSTAR1 protein. All these findings indicate that AtSTAR1 is involved in the basic detoxification of Al in Arabidopsis.
ATP 结合盒（ABC）转运蛋白是植物中一个庞大的家族，但这些转运蛋白的大多数功能尚不清楚。在这里，我们报道了一个基因 AtSTAR1，它只编码拟南芥（Arabidopsis thaliana）中一种细菌型 ABC 转运蛋白的 ATP 结合域。AtSTAR1 是水稻（Oryza sativa）OsSTAR1 的同源物，OsSTAR1 已被证明与铝（Al）耐受性有关。AtSTAR1 的敲除导致对 Al 的敏感性增加和开花提前。与 OsSTAR1 不同，AtSTAR1 在根和地上部分中均有表达，其表达不受 Al 或其他胁迫的诱导。通过 β-葡萄糖醛酸酶融合研究 AtSTAR1 的组织特异性定位表明，AtSTAR1 主要在根尖和发育中的叶片的外层细胞层中表达，其定位也与 OsSTAR1 不同。然而，将 OsSTAR1 导入 atstar1 突变体中挽救了 atstar1 对 Al 的敏感性，表明 AtSTAR1 具有与 OsSTAR1 相似的功能。此外，我们发现 AtSTAR1 可能与 ALS3 相互作用，ALS3 是拟南芥中的跨膜结合域，因为将 OsSTAR1（AtSTAR1 的功能替代物）导入 als3 突变体中会导致 OsSTAR1 蛋白的丢失。所有这些发现表明 AtSTAR1 参与了拟南芥中 Al 的基本解毒作用。
