Luan Sheng, Lan Wenzhi, Chul Lee Sung
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Curr Opin Plant Biol. 2009 Jun;12(3):339-46. doi: 10.1016/j.pbi.2009.05.003. Epub 2009 Jun 6.
Plant roots take up numerous minerals from the soil. Some minerals (e.g., K(+)) are essential nutrients and others (e.g., Na(+)) are toxic for plant growth and development. In addition to the absolute level, the balance among the minerals is critical for their physiological functions. For instance, [K(+)]/[Na(+)] ratio and homeostasis often determine plant growth rate. Either low-K or high-Na in the soil represents a stress condition that severely affects plant life and agricultural production. Earlier observations indicated that higher soil Ca2(+) improve plants growth under low-K or high-Na condition, implying functional interaction among the three cations. Recent studies have begun to delineate the signaling mechanisms underlying such interactions. Either low-K(+) or high-Na(+) can trigger cellular Ca2(+) changes that lead to activation of complex signaling networks. One such network consists of Ca2(+) sensor proteins (e.g., CBLs) interacting with their target kinases (CIPKs). The CBL-CIPK signaling modules interact with and regulate the activity of a number of transporting proteins involved in the uptake and translocation of K(+) and Na(+), maintaining the "balance" of these cations in plants under stress conditions.
植物根系从土壤中吸收多种矿物质。一些矿物质（如钾离子）是必需营养元素，而其他一些（如钠离子）对植物生长发育有毒害作用。除了矿物质的绝对含量外，它们之间的平衡对于其生理功能至关重要。例如，钾离子/钠离子比值和稳态常常决定植物的生长速率。土壤低钾或高钠均代表一种胁迫条件，会严重影响植物生长及农业生产。早期观察表明，较高的土壤钙离子浓度可改善低钾或高钠条件下植物的生长，这意味着这三种阳离子之间存在功能相互作用。最近的研究已开始阐明这种相互作用背后的信号传导机制。低钾或高钠均可引发细胞内钙离子变化，进而导致复杂信号网络的激活。其中一个这样的网络由钙离子传感蛋白（如CBLs）与其靶标激酶（CIPKs）相互作用组成。CBL-CIPK信号模块与许多参与钾离子和钠离子吸收及转运的转运蛋白相互作用并调节其活性，在胁迫条件下维持植物体内这些阳离子的“平衡”。
