Fuels for ROS signaling in plant immunity.

Plant defense responses against microbial pathogens rely on the innate immune system. Reactive oxygen species (ROS) are important secondary messengers that mediate downstream immune responses. Therefore, modification of ROS signaling contributes to crop plant breeding for broad-spectrum disease resistance. In plant immunity, ROS signaling is mainly mediated by NADPH oxidases, which use NADPH as a substrate to catalyze the reduction of oxygen to produce superoxide. NADPH generation is an important rate-limiting step in the ROS production pathway. Manipulation of the NADPH generation pathway may provide a novel strategy for regulating ROS signaling to improve broad-spectrum disease resistance of crop species. Reactive oxygen species (ROS) signaling has an important role in plant innate immune responses and is primarily mediated by NADPH oxidase, also known as respiratory burst oxidase homologs (RBOHs) in plants. NADPH serves as a fuel for RBOHs and limits the rate or amount of ROS production. Molecular regulation of RBOHs has been extensively studied; however, the source of NADPH for RBOHs has received little attention. Here, we review ROS signaling and the regulation of RBOHs in the plant immune system with a focus on NADPH regulation to achieve ROS homeostasis. We propose an idea to regulate the levels of NADPH as part of a new strategy to control ROS signaling and the corresponding downstream defense responses. [ABSTRACT FROM AUTHOR]