阳离子转运蛋白在调节细胞质阳离子浓度过程中发挥关键作用.液泡是一个储存多种离子的重要细胞器,阳离子(Ca<'2+>)/H+反向转运蛋白CAXs定位在液泡膜上,主要参与Ca<'2+>向液泡的转运,也参与其他阳离子的转运.近年来,植物中分离鉴定了多个CAX基因,植物CAXs主要有4个功能域:NRR通过自抑制机制调节Ca<'2+>转运活性,CaD和C功能域分别赋予CAXs的Ca<'2+>和Mn<'2+>专一性转运活性,D功能域可调节细胞质pH.拟南芥AtCAXs参与植物的生长发育和胁迫适应过程,AtCAX3主要在盐胁迫下转运Ca<'2+>,AtCAX2和AtCAX4在重金属胁迫下参与重金属离子(Cd<'2+>、zn<'2+>和Mn<'2+>)的转运和解毒过程,表明CAXs基因在强化植物营养和提高植物修复潜力方面有重要作用.以下主要综述植物CAXs的分类、结构及功能方面的研究进展.%Cation transporters play important roles in modulating the concentration of intracellular metal ions. The vacuole is an important storage organelle for many ions. Cation (Ca2+)/H+ antiporters (CAXs) located at vacuolar membrane are mainly involved in the Ca2+ flux into the vacuole, and appear to be capable of transporting various divalent cations to some degree.Several CAX genes have been isolated and characterized from various plants in recent years. Four domains of plant CAXs have been identified: NRR regulates Ca2+ transport by a mechanism of N-terminal autoinhibition; Ca domain and C domain confer Ca2+ and Mn2+ specificity among CAX transporters, respectively; D domain plays a part in the regulation of cytosolic pH. AtCAXs identified in Arabidopsis thaliana are involved in the growth, development and stress adaption of plant. AtCAX3 is the mainly Ca2+/H+ transporter in response to salt stress; AtCAX2 and AtCAX4 participate in transportation and detoxicification of heavy metal ions (Cd2+, Zn2+, and Mn2-) in cells under heavy metal stress, and impact root/shoot Cd partitioning in plant. These suggest that CAX genes may be useful for nutritional enhancement of plants, and for increasing phytoremediation potential. Here, the classification, structure and function of CAXs in plants are reviewed.
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