Use of Genetic Transformation for the Introduction of Flocculence into Yeast¹

1 Presented at the 45th Annual Meeting, Portland, OR, April 1979.

Abstract

Genetic transformation of flocculence in Saccharomyces cerevisiae was accomplished without a vector by the induced uptake of native yeast DNA by spheroplasted, nonflocculent recipients. Because flocculent transformants could not be selected on a solid medium and because the number of broth cultures required for selection would have been prohibitive, a system of cotransformation of an additional genetic marker was devised. The ade1 gene, which is linked to FLO1 on Chromosome I, was selected for cotransformation in this study. Nonflocculent ade1⁻recipients were transformed with DNA isolated from an ADE1⁺ FLO1⁺ donor. Adenine prototrophs were selected by growth on a minimal medium and by colonial pigment changes. These transformants were then further screened for flocculence by broth culturing. Eight percent of the adenine transformants had also acquired the FLO1 gene. Tetrad analyses of sporulated zygotes formed from the cross of a FLO⁺ ADE⁺ transformant with a flo1⁻ ade1⁻ mating strain showed typical Mendelian segregation of the newly acquired genes. As a control, spontaneous revertants to adenine prototrophy were shown to remain nonflocculent.

• Cotransformation
• Flocculence
• Genetic transformation
• Yeast