| Popis: |
Asexual yeast Dekkera bruxellensis can in nature be found in rather “hostile” niches, for example, characterized by high ethanol content and elevated acidity. D. bruxellensis shares several common features with Saccharomyces cerevisiae, like high ethanol production and ethanol tolerance, capability of anaerobic growth, and both are also Crabtree and petite positive. However, the two yeasts are not closely related and the two lineages separated at least 200 million years ago. In D. bruxellensis, the ploidy status, and the number and size of its chromosomes vary a lot (Eukaryot Cell, 2009, 8: 1739). Hereby we report on the development of a transformation system based on a ura3 mutant recipient strain and integrative and autonomous plasmids carrying the D. bruxellensis URA3 gene. For development of autonomous plasmids putative ARS/CEN elements were cloned from gene libraries. Even if this yeast has several chromosomes only three different types of loci (designated as CIGO 1, 2 and 3) were isolated from libraries prepared from different strains. Traces of S. cerevisiae centromeric CDEI, CDEII and CDEIII elements could be detected in all three loci. Surprisingly, in any tested strain each of these three loci hybridized to several different chromosomes. However, any chromosome in any studied strain hybridized to only one of the three loci. A significant biological activity was retained even when CIGO1 was shortened to 360 bp. The three putative ARS/CEN elements promoted the plasmid transmission during the cell division but the observed plasmid loss was between 10 – 66%. D. bruxellensis has a very dynamic genome and apparently its chromosomes can easily get reshaped if the environmental pressure changes. In this sense, D. bruxellensis reminds on the asexual Candida yeasts, which are very prone to reshape their genome (PNAS, 2009, 106: 2688) to promote the adaptation on more “hostile” environments. CIGO could represent a crucial genetic element promoting a faster reorganization of D. bruxellensis chromosomes and thereby increased adaptive ability of this yeast. |
