Stomata in plants play a crucial role in innate immunity against bacterial infection. When plant pathogenic bacteria, such as Pseudomonas syringae pv. tomato (Pst DC3000), come into contact with plant leaves, they trigger stomatal closure, which restricts bacterial entry. This response is mediated by the FLS2 receptor, nitric oxide production, and the guard-cell-specific OST1 kinase. However, Pst DC3000 has evolved virulence factors, such as the phytotoxin coronatine (COR), to counteract this defense by reopening stomata. COR acts downstream or independently of nitric oxide production to inhibit stomatal closure and is dependent on the COI1 subunit of an E3 ubiquitin ligase. This mechanism allows Pst DC3000 to overcome the innate immune response and infect plants. The study also shows that stomata are integral to the plant's innate immune system, and their closure is part of a broader defense strategy involving salicylic acid (SA) signaling. The findings highlight the evolutionary arms race between plants and pathogens, where plants use stomata as a barrier to prevent bacterial entry, while pathogens evolve strategies to bypass this defense. The research underscores the importance of stomatal defense in plant disease resistance and provides insights into the molecular mechanisms underlying plant immunity.Stomata in plants play a crucial role in innate immunity against bacterial infection. When plant pathogenic bacteria, such as Pseudomonas syringae pv. tomato (Pst DC3000), come into contact with plant leaves, they trigger stomatal closure, which restricts bacterial entry. This response is mediated by the FLS2 receptor, nitric oxide production, and the guard-cell-specific OST1 kinase. However, Pst DC3000 has evolved virulence factors, such as the phytotoxin coronatine (COR), to counteract this defense by reopening stomata. COR acts downstream or independently of nitric oxide production to inhibit stomatal closure and is dependent on the COI1 subunit of an E3 ubiquitin ligase. This mechanism allows Pst DC3000 to overcome the innate immune response and infect plants. The study also shows that stomata are integral to the plant's innate immune system, and their closure is part of a broader defense strategy involving salicylic acid (SA) signaling. The findings highlight the evolutionary arms race between plants and pathogens, where plants use stomata as a barrier to prevent bacterial entry, while pathogens evolve strategies to bypass this defense. The research underscores the importance of stomatal defense in plant disease resistance and provides insights into the molecular mechanisms underlying plant immunity.