The long-term goal is to dissect the reactive oxygen signaling network of cells and determine how reactive oxygen signals are sensed and transduced in eukaryotic cells. Reactive oxygen species (ROS) are at the core of every advanced biological system on our planet. They regulate basic processes such as development and growth, and play a key role in cancer, different neurodegenerative diseases and HIV. Nevertheless, ROS are toxic to cells. Controlling ROS toxicity, while enabling ROS to function as key signaling molecules, is thought to require a large gene network that was recently defined in the model plant Arabidopsis thaliana. Although the ROS network has been defined in Arabidopsis, many questions related to its mode of regulation and its modulation of networks that control basic biological processes in cells remain unanswered. Our specific aims are: 1. Identify and characterize ROS receptors from plant cells. The hypothesis being tested is that different sensors are used by plant cells to transduce different ROS signals. 2. Determine how different ROS signals, generated at different subcellular compartments, are integrated in cells. The hypothesis being tested is that cross-talk between different ROS signals, generated at different compartments, determines whether cells will survive during stress or undergo cell death. A combination of research tools, including genetics, molecular biology, advanced redox imaging, and bioinformatics, will be used to dissect the ROS network of plants. Specific findings will be tested using gain- and loss-of-function mutants. ROS are implicated in diverse biological processes including stress tolerance, aging and cancer. Because the potential risk of oxidative stress is common to all aerobic organisms, elucidating the ROS-signaling network of plants would have a significant impact in medicine and agriculture, bridging different disciplines and unraveling links between processes such as development, disease and stress.