Molecular identification of one event of Ds excision and re-insertion at two loci in rice genome.

: The maize Ac/Ds transposable elements are members of the hAT transposon superfamily, and have stable transpositional activity in transgenic rice plants. Ac/Ds transposable elements are considered to transpose via a conservative non-replicative "cut and paste" model, though their transposition mechanism is not completely understood. Previous studies have shown that Ds preferentially transposes to genetically linked sites after being excised from its original site in the presence of Ac-transposase. In this study, genomic sequences flanking Ds insertions from a Ds-tagged rice mutant and its rever- tant were determined by TAIL-PCR. The Ds insertion site, the excision footprint and the re-insertion sites in the mutant were identified using bioinformatics tool. The results showed that Ds element excised from its original insertion site on chromosome 3 by leaving an 8 bp footprint (CATCATGA), which resulted in exon changes in tagged gene. After the excision, Ds element was re-inserted into the coding sequences of two genes on chromosome 2 and chromosome 6, which encode a nicotianamine aminotransferase and a senescence-associated protein, respectively. The transposition behavior of Ds element in this study could not be fully explained by the "cut and paste" mechanism, while it is likely to transpose in a "cut and copy and paste" way.