Comparison of different constitutive and inducible promoters for the overexpression of transgenes in Arabidopsis thaliana.

We compared the organ specificity and the strength of different constitutive (CaMV-35S, CaMV-35Somega, Arabidopsis ubiquitin UBQ1, and barley leaf thionin BTH6 promoter) and one inducible promoter (soybean heat-shock promoter Gmhsp17.3) in stably transformed Arabidopsis thaliana plants. For this purpose we constructed a set of plant expression vectors equipped with the different promoters. Using the uidA reporter gene we could show that the CaMV-35S promoter has the highest expression level which was enhanced two- to threefold by the addition of a translational enhancer (TMV omega element) without altering the organ specificity of the promoter. The barley leaf thionin promoter was almost inactive in the majority of lines whereas the ubiquitin promoter exhibited an intermediate strength. The heat-shock promoter was inducible up to 18-fold but absolute levels were lower than in the case of the ubiquitin promoter. Conclusive quantitative results for different organs and developmental stages were obtained by the analysis of 24 stably transformed lines per promoter construct.