Stomata are specialised pores that mediate gas exchange and water loss in plants by changing their aperture. A number of ATP-binding cassette transporters are known to be involved in regulation of stomatal movements. Thus, ABCG22 has been shown to mediate stomatal closure in low air humidity conditions, but roles for ABCG22 and for another functionally related ABC transporter, ABCG21, in stomatal regulation has not been fully clarified. In this study, we demonstrate that ABCG22 is involved in stomatal movements induced by several environmental factors, such as low air humidity, ozone pulse, and CO2, while the abcg21 mutant showed wildtype stomatal responses to these stimuli. In addition, generation of transgenic plants expressing modified ABCG22 has been initiated.
