Novel and useful properties of a chimeric plant promoter combining CaMV 35S and MAS elements.

The CaMV 35S and Ti plasmid mannopine synthetase (mas) promoters are commonly used by plant genetic engineers. To combine their useful properties, we constructed hybrid promoters incorporating elements from both. These promoters were spliced to the beta-glucuronidase reporter gene and introduced into tobacco and tomato plants by Agrobacterium cocultivation. T1 and T2 transgenic plant populations transformed with different constructs were assayed for the marker enzyme. Comparisons were made based on the range of expression levels found for each promoter construct. We found that a hybrid promoter incorporating the mas region from +65 to -301 and the 35S enhancer region from -90 to -941 had new and interesting properties. This promoter, called Mac, expressed gus at a level three to five times that expressed by a double 35S promoter in the leaves, and 10 to 15 times in hypocotyls and roots. The Mac promoter, however, showed only marginal wound inducibility. Five- to seven-fold wound induction required the presence of the region from -301 to -613 of mas. Reiteration of the 35S enhancer region, from -90 to -430, behind the 35S TATA box region or the mas +65 to -301 region had a smaller effect on expression, ranging from equal to twice the level of the single enhancer control.