Overexpressing sweetpotato peroxidase gene swpa4 affects nitric oxide production by activating the expression of reactive oxygen species- and nitric oxide-related genes in tobacco

Abstract

Reactive oxygen species (ROS) and nitric oxide (NO) are key signaling molecules involved in various developmental and stress responses in plants. NO and ROS production, which is triggered by various stimuli, activates downstream signaling pathways to help plants cope with abiotic and biotic stresses. Recent evidence suggests that the interplay between NO and ROS signaling plays a critical role in regulating stress responses. However, the underlying molecular mechanism remains poorly understood. We previously reported that transgenic tobacco overexpressing the swpa4 peroxidase (POD) gene from sweetpotato exhibits increased tolerance to stress. Overexpression of swpa4 also induces the generation of H2O2 and activates the expression of various extracellular acidic pathogenesis-related (PR) genes. Here, we show that swpa4 positively regulates the expression of ROS- and NO-related genes in transgenic tobacco plants. Plants expressing swpa4 exhibited increased expression of ROS-related genes and increased ROS-related enzyme activity under normal conditions and H2O2 treatment, whereas the expression of NO associated 1 (NOA1) only increased under normal conditions. Moreover, plants overexpressing swpa4 showed increased NO levels under normal conditions and after treatment with the NO donor sodium nitroprusside (SNP). Interestingly, treatment with a POD inhibitor dramatically reduced NO levels in swpa4 transgenic plants. These findings suggest that swpa4 regulates H2O2 and NO homeostasis in plants under stress conditions, thereby establishing a possible molecular link between the NO and ROS signaling pathways.