DS ELEMENTS ON ALL 5 ARABIDOPSIS CHROMOSOMES AND ASSESSMENT OF THEIR UTILITY FOR TRANSPOSON TAGGING

The maize transposons Activator (Ac) and Dissociation (Ds) tend to tra nspose to sites close to their original position and can be efficientl y used to transposon-tag genetically linked genes. To facilitate this approach, we describe the locations of seven T-DNAs carrying Ds elemen ts, including at least one on each of the five chromosomes. For five o f these T-DNAs, we have confirmed that the Ds element transposes prefe rentially to genetically linked sites. A large-scale transposon-taggin g experiment was performed by activating Ds from eight chromosomal loc ations that included at least one on each of the five chromosomes. The se experiments produced a total of 1132 F-3 families that were predict ed to carry around 870 independent Ds insertions. In these populations , 33 independently isolated mutants that were visibly different from w ild-type were identified. Twenty-nine of these mutants were studied ge netically, and 14 were not tagged with Ds because the element could be separated from the mutation by recombination. The remaining 15 mutati ons were possibly tagged because the transposon and the mutation were not separated by recombination. These experiments provide tools for tr ansposon-tagging on each chromosome, and indicate that approximately 5 0% of identified mutations are likely to be tagged, thereby enabling c loning of the affected genes.