DISTRIBUTION OF UNLINKED TRANSPOSITIONS OF A DS ELEMENT FROM A T-DNA LOCUS ON TOMATO CHROMOSOME-4

In maize, receptor sites for unlinked transpositions of Activator (Ac) elements are not distributed randomly. To test whether the same is tr ue in tomato, the receptor sites for a Dissociation (Ds) element deriv ed from Ac, were mapped for 26 transpositions unlinked to a donor T-DN A locus on chromosome 4. Four independent transposed Dss mapped to sit es on chromosome 4 genetically unlinked to the donor T-DNA, consistent with a preference for transposition to unlinked sites on the same chr omosome as opposed to sites on other chromosomes. There was little pre ference among the nondonor chromosomes, except perhaps for chromosome 2, which carried seven transposed Dss, but these could not be proven t o be independent. However, these data, when combined with those from o ther studies in tomato examining the distribution of transposed Acs or Dss among nondonor chromosomes, suggest there may be absolute prefere nces for transposition irrespective of the chromosomal location of the donor site. If true, transposition to nondonor chromosomes in tomato would differ from that in maize, where the preference seems to be dete rmined by the spatial arrangement of chromosomes in the interphase nuc leus. The tomato lines carrying Ds elements at known locations are ava ilable for targeted transposon tagging experiments.