We have developed a novel transformation system for yeasts carrying no selectable markers. By using a plasmid, pYHH-1, containing an internal region of the CAN1 gene, a wild type yeast strain was endowed with L-canavanine resistance (canl) through integral disruption of the resident CAN1 gene. Diploid strains as well as haploids can be transformed, indicating that L-canavanine resistance can be used as a positive selectable marker for the transformation of industrial yeasts.
