Transposition pattern of a modified Ds element in tomato.

Several aspects of transposition of an in vitro modified Ds element are described. This Ds element, designated Ds-r, is equipped with bacterial plasmid sequences and can, therefore, be rescued from the plant genome. Our results indicate that the Ds-r element has a 'late' timing of transposition from T-DNAs. This feature of the element might be advantageous for tagging experiments because it leads to independently transposed germinally transmitted elements. Furthermore, it is shown that Ds-r transposition generates clusters of insertions, indicating that 'genes to be tagged' should be located in genomic regions covered by insertions.