Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan.
Biochem Biophys Res Commun. 2012 Oct 5;426(4):626-9. doi: 10.1016/j.bbrc.2012.08.141. Epub 2012 Sep 11.
Mitogen-activated protein kinases (MPKs) have roles in regulating developmental processes and responses to various stimuli in plants. Activations of some MPKs are necessary for proper responses to hyperosmolarity and to a stress-related phytohormone, abscisic acid (ABA). However, there is no direct evidence that MPK activations are regulated by drought and rehydration. Here we show that the activation state of one of the Arabidopsis MPKs, MPK6, is directly regulated by drought and rehydration. An immunoblot analysis using an anti-active MPK antibody detected drought-induced activation and rehydration-induced inactivation of MPK6. MPK6 was activated by drought even in an ABA-deficient mutant, aba2-4. In addition, exogenously added ABA failed to suppress the rehydration-dependent inactivation of MPK6. Under drought conditions, elevated levels of reactive oxygen species (ROS), which are known elicitors of MPK6 activation, were detected in both wild type and an MPK6-deficient mutant, mpk6-4. These results suggest that ROS, but not ABA, induces MPK6 activation as an upstream signal under drought conditions.
丝裂原活化蛋白激酶（MPKs）在调节植物的发育过程和对各种刺激的反应中发挥作用。某些 MPKs 的激活对于正确响应高渗和与应激相关的植物激素脱落酸（ABA）是必要的。然而，没有直接证据表明 MPK 激活受干旱和复水调节。在这里，我们表明拟南芥 MPK 之一 MPK6 的激活状态直接受干旱和复水调节。使用抗活性 MPK 抗体的免疫印迹分析检测到干旱诱导的 MPK6 激活和复水诱导的失活。即使在 ABA 缺陷突变体 aba2-4 中，干旱也能激活 MPK6。此外，外源添加的 ABA 未能抑制 MPK6 复水依赖性失活。在干旱条件下，在野生型和 MPK6 缺陷突变体 mpk6-4 中均检测到活性氧（ROS）水平升高，ROS 是已知的 MPK6 激活剂。这些结果表明，ROS 而不是 ABA，作为干旱条件下的上游信号诱导 MPK6 激活。
