CHARACTERIZATION OF A DISPERSED REPETITIVE DNA-SEQUENCE ASSOCIATED WITH THE CCDD GENOME OF WILD-RICE

A HindII repetitive fragment (pOD3) was isolated and cloned from the g enomic DNA of an accession of Oryza latifolia, a wild rice species tha t possesses a tetraploid CCDD genome. Southern blot analysis using thi s clone as a probe demonstrated that this repetitive DNA sequence had a dispersed organization in the CCDD genome and seemed to be highly sp ecific for this genome type. This fragment is the first CCDD-specific repeated DNA sequence to be described. The hybridization pattern is si milar for most CCDD accessions tested, although a few showed no hybrid ization signal. The nucleotide sequence of the element cloned in pOD3 was determined and analysed. The 1783 base pair long repeated sequence shows no homology with other known nucleotide sequences. In addition, none of the amino acid sequences deduced from the potential open read ing frames contained in the pOD3 repeat is homologous to any known pro tein. The nucleotide sequence presents several internal repeats, direc t or inverted, but their significance remains unknown.