CENTROMERIC DNA IN Beta SPECIES

Plant Molecular Cytogenetics Group Institute of Crop Science and Plant Breeding Christian Albrechts University of Kiel Olshausenstr. 40 D-24118 Kiel Germany

The centromere is defined as the chromosomal domain responsible for proper chromosome pairing and movement during mitosis and meiosis. Although the functional aspect is well defined, the structural components of centromeres are still elusive for most organisms, especially for higher eukaryotes. In the recent years a lot of effort has been spent on the isolation of centromeric sequences from different organisms. In a systematic screen for repetitive DNA in Beta species, we identified several repetitive DNA elements. Using fluorescence in-situ hybridization on metaphase spreads of Beta chromosomes we were able to identify clones associated with the centromeric region. Based on their chromosomal distribution these sequences split into four different groups. Genomic southern blotting and sequence analysis revealed that these clones belong to both satellite DNA and Ty3-gypsy-like retrotransposons. These elements are known to be components of centromeres. Our studies show that Beta centromeres are like their counterparts from other higher eukaryotes complex organized chromosomal domains consisting of a broad variety of different repetitive elements. As some of the characterized elements are species-specific they might be used for the identification and characterization of individual centromeres in monosomic addition lines.