Expression of the sweet potato peroxidase gene swpa4 in Arabidopsis activates defense genes mediated by reactive oxygen species and nitric oxide

Previously transgenic tobacco plants over-expressing the sweet potato peroxidase gene swpa4 exhibited increased tolerance to various stress conditions. Expression of swpa4 in tobacco also has a positive effect on expression of genes related to reactive oxygen species (ROS) and nitric oxide (NO). Expression levels of respiratory burst oxidase protein D ( RBOHD ), a major gene regulating ROS, and nitric oxide associated 1 ( NOA1 ), a gene involved in NO generation, are significantly affected by peroxidase inhibitor treatments. In this study, swpa4 was expressed in the rbohD and noa1 knock-out mutants of Arabidopsis, as well as in wild-type plants. The transgenic plants showed increased levels of ROS and NO. Expression of swpa4 activated expression of genes related to ROS and NO. This suggested that swpa4 regulated H 2 O 2 and NO homeostasis, thereby establishing a potential molecular link between the defense signaling pathways mediated by ROS and NO.