MAPK cascade and ROS metabolism are involved in GABA-induced disease resistance in red pitaya fruit

Abstract

This study investigates the effects of γ-Aminobutyric acid (GABA) and mitogen-activated protein kinase (MAPK) inhibitor (PD98059) in disease resistance in red pitaya fruit. Results demonstrated that GABA treatment suppressed the growth of Gilbertella persicaria; increased H2O2 content and O2•- production rate; enhanced reduced glutathione and ascorbic acid contents, as well as increased the activities and transcripts of catalase (CAT), NADPH oxidase (NOX), peroxidise (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR), and up-regulated HcMYB111/24 expressions. Furthermore, GABA promoted the expressions of HcMAPKKK1-HcMAPKK2/4-HcMAPK1/7 cascades. However, PD98059 +GABA treatment decreased the disease resistance against G. persicaria and reduced H2O2 content; inhibited the activities and gene expressions of NOX, CAT, SOD, POD, GR and APX, and down-regulated the expressions of HcMAPK1/7. These findings suggest that GABA induces disease resistance by regulating ROS metabolism and MAPK cascades in red pitaya fruit.