Reactive oxygen species (ROS) are produced in response to pathogen recognition, playing a critical role in plant defense. ROS, such as superoxide and hydrogen peroxide, are generated through oxidative bursts and can act as signaling molecules or directly contribute to pathogen cell death. The NADPH oxidase, also known as respiratory burst oxidase (RBO), is a key enzyme in ROS production, with homologs in plants like Arabidopsis. ROS production is also mediated by cell wall peroxidases, and these enzymes are induced by pathogen recognition. ROS can strengthen cell walls, cause membrane damage, and activate defense genes. ROS signaling is closely linked to salicylic acid (SA) and nitric oxide (NO), which regulate plant defense responses. ROS can also influence other signaling pathways, including calcium metabolism and ethylene signaling, which are involved in plant defense and stress responses. ROS production is essential for the hypersensitive response (HR), a form of programmed cell death that limits pathogen spread. However, some pathogens can exploit ROS production to enhance their own growth. ROS signaling is complex, with different ROS pools and signaling pathways interacting to mediate diverse defense responses. Genetic studies have shown that RBOH proteins are crucial for ROS production and defense responses. The interplay between ROS and other signaling molecules, such as SA and NO, is essential for coordinating plant defense mechanisms. Understanding the roles of ROS in plant defense is important for developing strategies to enhance disease resistance.Reactive oxygen species (ROS) are produced in response to pathogen recognition, playing a critical role in plant defense. ROS, such as superoxide and hydrogen peroxide, are generated through oxidative bursts and can act as signaling molecules or directly contribute to pathogen cell death. The NADPH oxidase, also known as respiratory burst oxidase (RBO), is a key enzyme in ROS production, with homologs in plants like Arabidopsis. ROS production is also mediated by cell wall peroxidases, and these enzymes are induced by pathogen recognition. ROS can strengthen cell walls, cause membrane damage, and activate defense genes. ROS signaling is closely linked to salicylic acid (SA) and nitric oxide (NO), which regulate plant defense responses. ROS can also influence other signaling pathways, including calcium metabolism and ethylene signaling, which are involved in plant defense and stress responses. ROS production is essential for the hypersensitive response (HR), a form of programmed cell death that limits pathogen spread. However, some pathogens can exploit ROS production to enhance their own growth. ROS signaling is complex, with different ROS pools and signaling pathways interacting to mediate diverse defense responses. Genetic studies have shown that RBOH proteins are crucial for ROS production and defense responses. The interplay between ROS and other signaling molecules, such as SA and NO, is essential for coordinating plant defense mechanisms. Understanding the roles of ROS in plant defense is important for developing strategies to enhance disease resistance.