TRANSPOSITION MEDIATED REPOSITIONING AND SUBSEQUENT ELIMINATION OF MARKER GENES FROM TRANSGENIC TOMATO

We describe a new plant transformation vector system which utilizes th e transposition functions of the maize Ac/Ds transposable element fami ly to re-position transgenes in transgenic crop plants. The practical applications of the system are two-fold. It allows the production of p lants which exhibit a range of different stabilizable transgene expres sion levels following a single primary transformation event, and it al lows for the elimination of specific transgene sequences-such as a sel ectable marker gene-subsequent to the transformation event. We have de monstrated the system using the NptII selectable marker gene and a Ds element containing the GUS reporter gene. Progeny plants were recovere d from primary transformants from which either the NptII gene or the D s/GUS element have been eliminated. We also show that the expression l evel of the GUS gene within both individual and amplified Ds elements can vary as a function of their position in the genome following trans position.