Dinitroaniline herbicide-resistant transgenic tobacco plants generated by co-overexpression of a mutant alpha-tubulin and a beta-tubulin.

Abstract

Dinitroaniline herbicides are used for the selective control of weeds in arable crops. Dinitroaniline herbicide resistance in the invasive weed goosegrass was previously shown to stem from a spontaneous mutation in an alpha-tubulin gene. We transformed and regenerated tobacco plants with an alpha/beta-tubulin double gene construct containing the mutant alpha-tubulin gene and showed that expression of this construct confers a stably inherited dinitroaniline-resistant phenotype in tobacco. In all transformed lines, the transgene alpha- and beta-tubulins increased the cytoplasmic pool of tubulin approximately 1.5-fold while repressing endogenous alpha- and beta-tubulin synthesis by up to 45% in some tissues. Transgene alpha- and beta-tubulin were overexpressed in every plant tissue analyzed and comprised approximately 66% of the total tubulin in these tissues. Immunolocalization studies revealed that transgene alpha- and beta-tubulins were incorporated into all four microtubule arrays, indicating that they are functional. The majority of the alpha/beta-tubulin pools are encoded by the transgenes, which implies that the mutant alpha-tubulin and the beta-tubulin can perform the majority, if not all, of the roles of microtubules in both juvenile and adult tobacco plants.