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Applied and Environmental Microbiology, April 2003, p. 2161-2165, Vol. 69, No. 4
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.4.2161-2165.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Karyotype Rearrangements in a Wine Yeast Strain by rad52-Dependent and rad52-Independent Mechanisms

Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, 08034 Barcelona,¹ Institut Català de la Vinya i el Vi, 08720 Vilafranca del Penedès, Barcelona, Spain²

Received 2 August 2002/ Accepted 18 January 2003

Yeast strains isolated from the wild may undergo karyotype changes during vegetative growth, a characteristic that compromises their utility in genetic improvement projects for industrial purposes. Karyotype instability is a dominant trait, segregating among meiotic derivatives as if it depended upon only a few genetic elements. We show that disrupting the RAD52 gene in a hypervariable strain partially stabilizes its karyotype. Specifically, RAD52 disruption eliminated recombination at telomeric and subtelomeric sequences, had no influence on ribosomal DNA rearrangement rates, and reduced to 30% the rate of changes in chromosomal size. Thus, there are at least three mechanisms related to karyotype instability in wild yeast strains, two of them not requiring RAD52-mediated homologous recombination. When utilized for a standard sparkling-wine second fermentation, rad52 strains retained the enological properties of the parental strain, specifically its vigorous fermentation capability. These data increase our understanding of the mechanisms of karyotype instability in yeast strains isolated from the wild and illustrate the feasibility and limitations of genetic remediation to increase the suitability of natural strains for industrial processes.