General structure of subtelomeres is conserved in hemiascomycetes.
Cecile Fairhead, Bernard Dujon
Struct and Dynamics of Genomes, Institut Pasteur, 25 rue du Dr Roux, Paris, 75015, France
Subtelomeric sequences in many organisms are known to harbour genes that allow rapid adaptation of the organism to its environment, called 'contingency genes'. In the yeast S. cerevisiae, where subtelomeres are best studied (EJ Louis, 1995, Yeast 11(16): 1553-73), these regions have been shown to be polymorphic, to contain many genes that are part of paralogous families, and to be able to give rise to novel genes by recombination (Ricchetti et al. 2003, J Mol Biol. 328: 847-62). We have analysed the subtelomeric composition of chromosomes from several hemiascomycetes that have recently been sequenced: Candida glabrata, Kluyveromyces lactis, Debaryomyces hansenii, Yarrowia lipolytica (B Dujon et al., 2004, Nature 430:35-44.), Kluyveromyces waltii (M Kellis et al., 2004, Nature 428:617-24) and Ashbya gossypii (Dietrich et al., 2004, Science 304:304-7). This analysis shows that the general structure of subtelomeres is conserved, even though there is no conservation of the gene families that are present (Fabre et al., in press, Mol Biol Evol). A partial map of K. lactis subtelomeres has been published previously (Nickles and McEachern, 2004, Yeast 21: 813-830). We now report a complete map from the sequenced strain, showing large duplicated segments, paralogous gene families and gene relics. Furthermore, some of these genes contain minisatellite repeats that make them ideal candidates for being contingency genes.