Differential Expression of rolC Results in Unique Plant Phenotypes

Abstract

Expression of the rolC gene in plants has been shown to cause pleiotropic effects, including decreased height. The effects of differential rolC gene expression on plant height, leaf color, root growth, leaf size, corolla length, and stem diameter were determined. Differential expression of rolC in Nicotiana tabacum L. `Samsun' plants was achieved using the 35S promoter, the light-inducible rbcS promoter, or the native rolC promoter. Sixteen plants from the T1 generation—six with the 35S promoter, six with the rbcS promoter, and four with the native rolC promoter—and non-transformed controls were measured for height, internode length, branch number, bud size, corolla length and diameter, root growth, and the number of days to flowering. Steady state mRNA levels of rolC were measured in roots, stems, and leaves to assess relationships between rolC expression level in specific tissues and phenotypes. Plants expressing rolC showed a wide range of phenotypes, with the largest changes in plants expressing rolC using the 35S promoter, which also had the highest rolC mRNA levels. Plants expressing rolC with the rolC or rbcS promoter had significant changes for many measured traits, despite rolC mRNA levels that were not significantly different from non-transformed controls. In general, as rolC mRNA levels increased, so did the severity of the rolC phenotype observed. Three plants, A4, A7, and B9, had unique combinations of traits that did not follow this general trend. Transformation with rolC can be useful in ornamental crops where smaller cultivars are desired.