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Applied and Environmental Microbiology, August 2004, p. 4686-4691, Vol. 70, No. 8
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.8.4686-4691.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Genetic Instability of Heterozygous, Hybrid, Natural Wine Yeasts

Manuel Ramírez,^1* Antonia Vinagre,¹ Jesús Ambrona,¹ Felipe Molina,² Matilde Maqueda,¹ and José E. Rebollo³

Departamento de Microbiología,¹ Departamento de Genética, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain,³ Department of Cell Biology, Institute for Cancer Research, Montebello, 0310 Oslo, Norway²

Received 16 December 2003/ Accepted 30 April 2004

We describe a genetic instability found in natural wine yeasts but not in the common laboratory strains of Saccharomyces cerevisiae. Spontaneous cyh2^R/cyh2^R mutants resistant to high levels of cycloheximide can be directly isolated from cyh2^S/cyh2^S wine yeasts. Heterozygous cyh2^R/cyh2^S hybrid clones vary in genetic instability as measured by loss of heterozygosity at cyh2. There were two main classes of hybrids. The lawn hybrids have high genetic instability and generally become cyh2^R/cyh2^R homozygotes and lose the killer phenotype under nonselective conditions. The papilla hybrids have a much lower rate of loss of heterozygosity and maintain the killer phenotype. The genetic instability in lawn hybrids is 3 to 5 orders of magnitude greater than the highest loss-of-heterozygosity rates previously reported. Molecular mechanisms such as DNA repair by break-induced replication might account for the asymmetrical loss of heterozygosity. This loss-of-heterozygosity phenomenon could be economically important if it causes sudden phenotype changes in industrial or pathogenic yeasts and of more basic importance to the degree that it influences the evolution of naturally occurring yeast populations.

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* Corresponding author. Mailing address: Departamento de Microbiología (Antiguo Rectorado), Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain. Phone: 34-24-289426. Fax: 34-24-289420. E-mail: mramirez{at}unex.es.

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Applied and Environmental Microbiology, August 2004, p. 4686-4691, Vol. 70, No. 8
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.8.4686-4691.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Ramirez, M., Ambrona, J. (2008). Construction of Sterile ime1{Delta}-Transgenic Saccharomyces cerevisiae Wine Yeasts Unable To Disseminate in Nature. Appl. Environ. Microbiol. 74: 2129-2134 [Abstract] [Full Text]  
• Ambrona, J., Ramirez, M. (2007). Analysis of Homothallic Saccharomyces cerevisiae Strain Mating during Must Fermentation. Appl. Environ. Microbiol. 73: 2486-2490 [Abstract] [Full Text]