ISOLATION AND IDENTIFICATION OF A NONSPECIFIC TANDEMLY REPEATED DNA-SEQUENCE IN ORYZA SPECIES

A tandemly repeated DNA sequence (RRS7) was isolated from Oryza alta ( CCDD). RRS7-related sequences were also found tandemly arrayed in geno mes AA, BB, BBCC, CC, and EE, and a small amount of RRS7-related seque nces were detected in genome FF and the Oryza species with unknown gen omes. DNA sequence analysis of the 1844-bp insert of RRS7 revealed tha t it contained six tandemly repeated units, of which five were 155 bp in length and one was 194 bp in length and contained an imperfect inte rnal 39-bp duplication. Southern blot analysis showed that the boundar y sequence contained in RRS7 is a single-copy sequence. A 155-bp conse nsus sequence derived from the six monomeric repeats contained no inte rnal repeat and showed no significant homology to other currently know n sequences. The results of Southern blot and sequence analysis reveal ed that there are at least two subfamilies present in the RRS7 family; these are represented by the DraI site and the MspI site, respectivel y. Restriction digestion with two pairs of isoschizomers MboI/Sau3A an d MspI/HpaII demonstrated that most of the C residues in the GATC site s and the internal C in the CCGG sites of the RRS7 family in O. alta w ere methylated. The usefulness of the RRS7 family in determining the e volutionary relationship of the genome DD and other Oryza genomes is d iscussed.