WILD-TYPE STRAINS OF DICTYOSTELIUM-DISCOIDEUM CAN BE TRANSFORMED USING A NOVEL SELECTION CASSETTE DRIVEN BY THE PROMOTER OF THE RIBOSOMAL V18 GENE

Almost all methods for transformation of the social ameba Dictyosteliu m discoideum rely on axenic growth, that is, growth in a synthetic med ium, for at least part of the procedure. Axenic growth requires severa l mutations. Here we describe a procedure that can be used to transfor m wild-type strains which are able to grow only on the natural food so urce, bacteria. The method relies on a new selection cassette driven b y the V18 promoter, a promoter that we show is substantially more acti ve during growth on bacteria than the actin-6 promoter, which is widel y used for axenic transformation. The procedure gives transformation f requencies of about 10(-5) with both strains Ax2 (capable of axenic gr owth) and NC4 (capable of growth only on bacteria). Using this vector, we have obtained NC4 strains carrying several beta-galactosidase repo rter cassettes. Our Vector can also be used in axenic transformations. (C) 1996 Academic Press.