The maize alternative oxidase 1a (Aox1a) gene is regulated by signals related to oxidative stress

We isolated and characterized the expression of Aox1a, a member of the maize alternative oxidase (Aox) small multigene family. Aox1a consists of four exons interrupted by three introns and its promoter harbors diverse stress-specific putative regulatory motifs pointing to complex regulation and response to multiple signals. Responses of Aox1a to such signals were examined and compared with those of maize glutathione S-transferase I ( GstI), a typical oxidative stress inducible gene. Potassium cyanide (KCN) and hydrogen peroxide ( H2O2) induced a rapid increase of the Aox1a and GstI transcripts, which was persisted in prolonged treatment at high H2O2 concentration only for Aox1a. High concentration of salicylic acid ( SA) and salicyl hydroxamic acid ( SHAM) induced Aox1a mRNA only after prolonged exposure, while GstI displayed an early strong induction, which declined thereafter. Nitric oxide ( NO) induced a high increase of Aox1a after prolonged exposure at high concentration, while GstI displayed a weak response. Our results show that multiple signaling pathways, involved in stress responses, also participate and differentially regulate Aox1a and GstI in maize. A ROS-depended signaling event may be involved, suggesting an essential role of Aox1a under oxidative stress in maize.