ISOLATION OF NOVEL REPETITIVE ELEMENTS FROM WHEAT AND BARLEY GENOMES

Laboratory of Plant Genetics Graduate School of Agriculture Kyoto University Sakyo-ku, Kyoto 606-8502 JAPAN

We report novel repetitive elements isolated from wheat and barley genomes by different molecular techniques. A 130-bp AFLP fragment of wheat with high band intensity was cloned and sequenced. Southern hybridization of the cloned fragment to wheat and barley genomic DNA digests indicated that the repetitive sequence is specific to wheat. The repetitive element seems to be dispersed in wheat genome because no obvious ladder pattern was observed in Southern hybridizations. A Genbank database search revealed significant levels of homology with many rice BAC-end-sequences and a TY3/gypsy type retrotransposon in rice. This suggests that the fragment is part of a retrotransposon of the Ty3/gypsy type. In situ hybridization on wheat metaphase chromosomes showed that the elements are dispersed in all wheat chromosomes. Repetitive elements that are specific to barley chromosomes were cloned by a PCR-based method using the primers homologous to the LTR (Long Terminal Repeat) and integrase regions of the cereal-centromere-specific retrotransposon. Southern and in situ hybridization experiments showed that the elements are specific to barley chromosomes and dispersed within them. No in situ hybridization signals were detected in the centromeric and telomeric regions of barley chromosomes. Nucleotide sequences analysis of the six cloned elements showed 95% homology. No obviously homologous sequences were found by database search, indicating that the element is a novel repetitive element specific to barley genome.