G418 resistance in the yeast Saccharomyces cerevisiae: comparison of the neomycin resistance genes from Tn5 and Tn903

Summary The neo genes of Tn5 and Tn903 (Tn601) coding for amigoglycoside phosphotransferase type II and type I, respectively, were joined to the yeast adc 1 promoter and trp1 terminator and introduced into yeast (Saccharomyces cerevisiae) cells. Transformants were obtained by direct selection for G418 resistance. Plasmids containing the Tn5 neo gene induced antibiotic resistance only at low frequency, whereas colonies transformed with the Tn903 neo gene could be selected at high frequency (300–400 transformants/g plasmid DNA). The resistance threshold of transformed strains was increased to 30 mg G418/ml by both genes and high level expression of the bacterial genes in yeast could be shown using an in vitro phosphotransferase assay. The results indicate that this system can be used for high frequency transformation of wild-type strains and might in addition be used for the identification and isolation of promoter-active sequences.Abbreviations adc 1 alcoholdehydrogenase I gene - APH aminoglycoside-3-phosphotransferase - leu2 -isopropylmalate dehydrogenase gene - neo aminoglycoside-3-phosphotransferase gene - trp1 N-(5-phosphoribosyl)-anthranilate isomerase gene Dedicated to Prof. Dr. Dr. h. c. Karl Esser on the occasion of his 65th birthday