In this study, the role of the rice (Oryza sativa L.) histidine kinase OsHK3 in abscisic acid (ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2 O2 , and polyethylene glycol (PEG) induced the expression of OsHK3 in rice leaves, and H2 O2 is required for ABA-induced increase