Transposon tagging of the Sulfur gene of tobacco using engineered maize Ac/Ds elements

The Sulfur gene of tobacco is nuclearly encoded. A Su allele at this locus acts as a dominant semilethal mutation and causes reduced accumulation of c hlorophyll, resulting in a yellow color in die plant. An engineered transpo son tagging system, based upon the maize element Ac/Ds, was used to mutate the gene. High frequency of transposon excision from the Su locus produced variegated sectors. Plants regenerated from the variegated sector exhibited a similar variegated phenotype. Genetic analyses showed that the variegati on was always associated with the transposase construct and the transposon was linked to the Su locus. Sequences surrounding the transposon were isola ted, and five revertant sectors possessed typical direct repeats following Ds excisions. These genetic and molecular data are consistent with the tagg ing of the Su allele by the transposon.