BIOCHEMICAL AND STRUCTURAL ANALYSIS OFABA SIGNALING PROTEINS

Abstract

Drought is a major problem for plants and they have developed several stress adaptive mechanisms for survival. Abscisic acid (ABA) signaling has long been attributed as a master mechanism, regulating various stress adaptive responses in plants. The three major components of the ABA signaling pathway are the PYR1/PYL ABA receptors, PP2C protein phosphatase and SnRK2 protein kinase. Our study focuses on the crosstalk between the ABA signaling and hydrogen peroxide mediated ROS signaling in plants. PP2Cs, including HAB1, act as redox sensors during oxidative stress. Hydrogen peroxide can reversibly inhibit HAB1 by oxidising its Cys186 and Cys274 to form inactive dimers, which are incapable of inhibiting the kinase activity of SnRK2. Furthermore, we report for the first time that all the three components of the ABA signaling can interact to form a transient quaternary complex in the presence of ABA. Also, there is a direct interaction between the receptor PYR1 and kinase SnRK2 which may serve as a receptor desensitization mechanism.