"The production of Reactive Oxygen Species (ROS) is one of the earlier responses observed after pathogen infection in plants. It is becoming evident that ROS are not direct killers but signals that mediate the activation of the plant defenses as well as other responses to the environment, developmental processes and Programmed Cell Death (PCD). This topic is of such importance in plant biology that it was recently the subject of a Special Issue in Plant Physiology (June, 2006), were the importance of the NADPH oxidase was specially outlined. Plants use ROS-derived signals in a variety of developmental contexts and in response to both biotic and abiotic stress. It is hence important to understand the signaling controls that allow plant cells to interpret ROS-dependent signals. Our goal is to decipher, using functional genomics tools, the functions of the plant NADPH oxidase gene family. Different members of the rboh (respiratory burst oxidase homologues) family, components of the plant NADPH oxidase, control production of ROS during defense and other responses. We will perform this research in Arabidopsis, model organism for studies in plants, where many genomic tools are available. We intend to further the identification of the factors that regulate Atrboh function, as well as putative targets or mediators of ROS-dependent signaling. It has been suggested that phosphorylation events and Ca++ signaling are implicated in this regulation. In addition, many evidences suggest the existence of a crosstalk between ROS and other signaling molecules like salicylic acid (SA) and abscisic acid (ABA). We are particularly interested in the signaling interaction between ROS and heterotrimeric G proteins that mediate responses like pathogen defense and stomata closure. These studies will allow us to further understand the function of ROS not only in disease resistance, but also in other responses to the environment and developmental processes."