Postinvasive Bacterial Resistance Conferred by Open Stomata in Rice

Stomata are leaf pores that regulate gas exchange and water transpiration in response to environmental cues. They also function in innate immunity by limiting pathogen entry through actively closing in so-called stomatal defense. However, roles of stomata in plant disease resistance are not fully elucidated, especially in monocots. Here, we report that non–race specific resistance of the rice abscisic acid-deficient mutant Osaba1 to Xanthomonas oryzae pv. oryzae is due to increased stomatal conductance. Reducing stomatal conductance in the Osaba1 mutant increases its susceptibility to X. oryzae pv. oryzae. Artificial opening of stomata in wild-type plants leads to enhanced resistance to X. oryzae pv. oryzae. The rice mutant es1-1 with constitutively higher stomatal conductance exhibits strong resistance to X. oryzae pv. oryzae. Additionally, Osaba1 and es1-1 are resistant to X. oryzae pv. oryzicola. The data support that open stomata confer postinvasive resistance against bacterial pathogens in rice, and such resistance probably results from decreased leaf water potential. Our findings reveal a novel role of stomata in plant immunity through modulation of leaf water status, which provides physiological insight into the interactions between plant, pathogen, and environment.