Single-step Marker Switching in Using a Lithium Acetate Transformation Protocol.

The ability to utilize different selectable markers for tagging or mutating multiple genes in is hampered by the historical use of only two selectable markers, and ; the latter conferring resistance to the antibiotic G418 (geneticin). More markers have been described recently, but introducing these into yeast cells often requires strain construction from scratch. To overcome this problem we and other groups have created transformation cassettes with flanking homologies to and which enable an efficient and time-saving way to exchange markers in existing mutated or tagged fission yeast strains. Here, we present a protocol for single-step marker switching by lithium acetate transformation in fission yeast, . In the following we describe how to swap the marker to a or marker, which provide resistance against the antibiotics G418, nourseothricin (clonNAT) or hygromycin B, respectively. We also detail how to exchange any of the markers for nutritional markers, such as and .