TRANSPOSITION PATTERN OF A MODIFIED DS ELEMENT IN TOMATO

Several aspects of transposition of an in vitro modified Ds element ar e described. This Ds element, designated Ds-r, is equipped with bacter ial plasmid sequences and can, therefore, be rescued from the plant ge nome. Our results indicate that the Ds-r element has a 'late' timing o f transposition from T-DNAs. This feature of the element might be adva ntageous for tagging experiments because it leads to independently tra nsposed 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 i nsertions.