Expression pattern and core region analysis of AtMPK3 promoter in response to environmental stresses

The protein kinase AtMPK3, a component of the MAP kinase cascade, plays an important role in stress signal transduction in plant cells. To clarify how AtMPK3 is regulated at the transcriptional level in response to various environmental factors, the 1016-bp promoter sequence upstream of the transcription start site of the AtMPK3 gene was isolated. Analyses of the promoter sequence using plant promoter databases revealed that the AtMPK3 promoter contains many potential cis-acting elements involved in environmental stress responses. We constructed four deletion mutants of the AtMPK3 promoter, and introduced the intact and truncated promoter sequences fused to the beta-glucuronidase (GUS) gene into Arabidopsis. GUS histochemical staining and quantitative fluorometric GUS assays were performed to visualize and compare the expression patterns in response to different environmental stimuli. The region between -188 and -62 upstream of the transcription start site was identified as the essential DNA sequence of the AtMPK3 promoter for responses to drought, high salinity, low temperature, and wounding. These results advance our understanding of the molecular mechanisms controlling AtMPK3 expression in response to different environmental stimuli.