Extracellular ATP mediates H 2 S-regulated stomatal movements and guard cell K + current in a H 2 O 2 -dependent manner in Arabidopsis

Hydrogen sulfide (H 2 S) is a newly discovered gaseous signaling molecule and involved in ethylene and ABA-induced stomatal closure. As an important factor, extracellular ATP (eATP) was believed to participate in regulation of stomatal closing. However, the mechanism by which eATP mediates H 2 S-regulated stomatal closure remains unclear. Here, we employed Arabidopsis wild-type and mutant lines of ATP-binding cassette transporters ( Atmrp4 , Atmrp5 and their double mutant Atmrp4/5 ) to study the function of eATP in H 2 S-regulated stomatal movement. Our results indicated that H 2 S affected stomatal closing through stimulating guard cell outward K + current. Moreover, we found that H 2 S induced eATP generation by regulating the activity of an ABC transporter. The inhibitor of ABC transporters, glibenclamide (Gli), could impair H 2 S-regulated stomatal closure and reduce H 2 S-dependent eATP accumulation in Atmrp4 and Atmrp5 mutants. In addition, the promotion effect of H 2 S on outward K + currents was diminished in Atmrp4/5 double mutant. Our data suggested that hydrogen peroxide (H 2 O 2 ) is required for H 2 S-induced stomatal closure, and the production of H 2 O 2 is regulated by eATP via NADPH oxidase. Based on this work, we conclude that H 2 S-induced stomatal closure requires ABC transporter-dependent eATP production and subsequent NADPH oxidase-dependent H 2 O 2 accumulation.