[12] High-efficiency transformation of yeast by electroporation

This chapter presents the procedure for high-efficiency transformation of yeast by electroporation. The protocol are designed by adapting the principles of bacterial electroporarion to transformarion of Saccharomyces cerevisiae, taking care, in addition, to provide continuous osmotic support of the electrically compromised cells. Preparation of cells in advance of electroporation involves four 5-min centrifugations. There is minimal preincubation with DNA and no carder nucleic acid, and the pulse itself takes only a moment. Subsequent outgrowth is not required, and plating by spreading is sufficient to provide maximal efficiency. A prerequisite for molecular biological manipulation of any organism is a reliable and efficient means for introducing exogenous DNA into the cell. Yet each of the techniques in general use for transforming yeast—namely, lithium acetate transformation and spheroplast transformation, suffers from significant limitations. Lithium acetate transformation, although relatively fast and simple, provides only a low efficiency of DNA transfer (∼l03 colonies/μg of episomal plasmid). Spheroplast transformation, while more efficient (∼1–5 × 104 colonies/μg), is complicated and time consuming.