Investigation of rDNA of Vitis vinifera L.: sequence analysis and physical mapping.

Here we report the first results of a study on 5S rRNA of Vitis vinifera. 5S rDNA sequences from five genotypes were amplified by PCR, cloned and sequenced. Three types of repeat variants were found. Two variants, denominated long-repeat and short-repeat, appeared to be the main components of the 5S rDNA of this species since they were found in all genotypes analyzed. They markedly differ each other both in the length and nucleotide composition of the spacers. They The third variant, classified as DEL-short-repeat, differs from the short-repeat due to a large deletion in the spacer region. It appears to be the most recent repeat type since it has been identified only in one genotype. The organization of the 5S rDNA unit variants was investigated by amplifying the genomic DNA with primers designed on the sequence of the long and short spacers. The PCR-amplified fragments showed that the long repeat is associated with the other two indicating that, in V. vinifera, different repeats units coexist within the same tandem array. The FISH analysis demonstrated that 5S rRNA genes are localized at a single locus. The variability of 5S rDNA repeats has been discussed in relation to the putative allopolyploid origin of V. vinifera.