Electroporation of Schizosaccharomyces pombe

Many of the techniques that have been developed for the manipulation of the budding yeast Saccharomyces cerevisiae have now been adapted to be used on the alternative host, Schizosaccharomyces pombe . One particularly important technique is the introduction of exogenous DNA into the yeast cell. One of the earlier methods requires generating protoplasts with a cell-wall-degrading enzyme prior to the introduction of DNA, generally giving transformation efficiencies of 2–3 � 10⁴ transformants/�g DNA (1 ). When combined with the cationic liposome-forming reagent Lipofectin, the protoplast method can generate transformation efficiencies of 7.0 � 10⁵ transformants/�g DNA (2 ). Protocols for transforming intact yeast have been developed that involve treatment of cells with monovalent cations, polyethylene glycol (PEG), and a 25-min heat pulse (3 ,4 ). Although the transformation efficiencies by these methods are lower than those of the standard protoplast method, they are not as tedious or time-consuming. Electroporation, subjecting cells to a controlled electrical pulse, is a transformation technique that has recently gained popularity. The main advantage of electroporation is the ease and time required to generate transformants. In addition, because of its biophysical nature, electroporation works well with a wide variety of cell types (5 –8 ). It has also been used to incorporate a number of different molecules into cells (9 –12 ). The procedure for electroporation presented below was developed as an easier and less time-consuming alternative for transformation of S. pombe .