Ca²⁺-ROS signaling network regulating defense and cell fate.

Abstract

Ca²⁺ mobilization by Ca²⁺ channels and production of reactive oxygen species (ROS) are often induced concomitantly during biotic/abiotic stress responses and development in plants. ROS-activated Ca²⁺ channels have also been postulated to play critical roles. Ten respiratory burst oxidase homolog (rboh) genes (AtrbohA-J) have been implicated in ROS production in Arabidopsis. By applying a heterologous expression system using HEK293T cells, we recently showed that AtrbohC and D possess ROS-producing activity synergistically activated by binding of Ca²⁺ to the EF-hand region of the cytosolic domain and phosphorylation. (Ogasawara et al. JBC 2008; Takeda et al. Science 2008). Ca²⁺-triggered activation of rboh-mediated ROS production and Ca²⁺ mobilization activated by ROS could establish a positive feedback loop to amplify intracellular and intercellular signals. To understand the significance and regulation of ROS production, we have been extensively characterizing rboh genes using the heterologous expression system. We will report comparative analyses of ROS-producing activities and regulatory mechanisms of various rboh proteins, and discuss their functional significance.