Differential Expression of rolC Results in Unique Plant Phenotypes

Abstract

As residential lot sizes decrease, there is an increased demand for new, small-statured landscape plants to fit into the smaller lots. One promising method to create smaller plants is by introducing a dwarfing gene into a plant of interest. A dwarfing gene that has been identified is the rolC gene from Agrobacterium rhizogenes. Expression of rolC in plants has been shown to cause decreased height and internode length, increased branching, and modified leaf size in a several species. Although the effects of the rolC gene have been well characterized for many plant species, most research has concerned the native promoter or the CaMV 35S promoter. Less research has been done with additional promoters or comparing the results from different promoters. In this study we examined the effects of three separate gene constructs, all containing rolC driven under either the 35S promoter, the light inducible rbcs promoter, or the native rolC promoter in tobacco. Plants transformed with these constructs ranged widely for height and other phenotypic traits. Representative plants were crossed back to wild-type tobacco. Plants from this next generation, six with the 35S promoter, six with the rbcs promoter and four with the native rolC promoter, were measured for traits such as height, days to flower, number of branches and internode length. RolC RNA expression levels were also measured in roots, stems, and leaves to determine correlations between rolC expression level in specific tissues and the observed phenotype. Information about these relationships can be used to provide insight into the use of rolC in ornamental plants and the potential to modify its phenotypic effects by controlling expression level.