Carbon Monoxide-induced Stomatal Closure Involves Generation of Hydrogen Peroxide in Vicia faba Guard Cells

Here the regulatory role of CO during stomatal movement in Vicia faba L. was surveyed. Results indicated that, like hydrogen peroxide (H(2)O(2)), CO donor Hematin induced stomatal closure in dose- and time-dependent manners. These responses were also proven by the addition of gaseous CO aqueous solution with different concentrations, showing the first time that CO and H(2)O(2) exhibit the similar regulation role in the stomatal movement. Moreover, our data showed that ascorbic acid (ASA, an important reducing substrate for H(2)O(2) removal) and diphenylene iodonium (DPI, an inhibitor of the H(2)O(2)-generating enzyme NADPH oxidase) not only reversed stomatal closure by CO, but also suppressed the H(2)O(2) fluorescence induced by CO, implying that CO induced-stomatal closure probably involves H(2)O(2) signal. Additionally, the CO/NO scavenger hemoglobin (Hb) and CO specific synthetic inhibitor ZnPPIX, ASA and DPI reversed the darkness-induced stomatal closure and H(2)O(2) fluorescence. These results show that, perhaps like H(2)O(2), the levels of CO in guard cells of V. faba are higher in the dark than in light, HO-1 and NADPH oxidase are the enzyme systems responsible for generating endogenous CO and H(2)O(2) in darkness respectively, and that CO is involved in darkness-induced H(2)O(2) synthesis in V. faba guard cells.