title: Drought-induced activation and rehydration-induced inactivation of MPK6 in Arabidopsis.
abstract: 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.
authors.affiliation: Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan. tsugama@anesc.u-tokyo.ac.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsugama
authors.forename: Shenkui
authors.initials: S
authors.lastname: Liu
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takano
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000235:genetics; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000096:biosynthesis* / Q000235:genetics; D055864:Droughts; D004789:Enzyme Activation; D055786:Gene Knockout Techniques; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis* / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013312:Stress, Physiological; D014867:Water / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; D014867:Water; D000040:Abscisic Acid; C469255:ABA2 protein, Arabidopsis; D000429:Alcohol Oxidoreductases; C436293:MPK6 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases