Promoter strength comparisons of maize shrunken 1 and alcohol dehydrogenase 1 and 2 promoters in mono- and dicotyledonous species

Abstract

Promoter strengths of two maize alcohol dehydrogenase genes, Adh1 and Adh2, and the maize shrunken-1 gene, Sh1, were evaluated by transient expression in cultured protoplasts of Panicum maximum, Triticum monococcum, and Daucus carota. Promoter elements were ligated in correct and opposite orientations as transcriptional gene fusions to the chloramphenicol acetyl transferase gene containing the nopaline synthase 3' polyadenylation signal. The relative levels of gene expression were compared to the cauliflower mosaic virus 35S promoter. The full length Adh1 promoter (-1100 to +15) functioned in all species, but at a reduced level in D. carota. An Adh1 promoter deletion from -304 to -1100 did not express at detectable levels in any species nor did the Sh1 promoter construction. The Adh2 promoter (-860 to +90) only expressed in D. carota. The full length Adh1 promoter gave the highest level of CAT expression in the monocot cells but at levels which were approximately 30% compared to the CaMV 35S promoter. This was reduced further in D. carota to approximately 4%. These data suggest that at least some of the regulatory factors responsible for promoter function are somewhat species specific and that these differences should be considered in gene expression studies.