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Letter from Peter T. Magee to Joshua Lederberg

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  • Medicine


UNIVERSITY OF MINNESOTA Twin Cities Campus July 2, 1991 Of&e of the Dean College of Biological Sciences 123 Snyder Hall 1475 Gortner Avenue St. Paul, MN55108-IO95 612-624-2244 Dr. Joshua Lederberg The Rockefeller University 1230 York Avenue New York, NY 10021 Fax: 612-624-2785 Dear Josh: Quite belatedly, I’m sending you several reprints on the switching phenomen Candida. We have a paper we’re about to submit on the genetics of the process you that one as soon as it’s ready to go to the journal. As you can see, there are two kinds of switching: one affects the regulation of the yeast-to- hyphal transition (the colony morphology switch), while the other (the white-opaque transition) causes cells to switch back and forth between a normal and an abnormal cell shape. Their common characteristics are that they can occur with roughly the same frequency (10-4-10-5 per cell division) and that both are recessive. They differ in several ways: induction of colony morphology switching (CM) variants appears to be possible even from strains that don’t make hyphae very well; the hyphal products appear to be normal, and there is a variety of different phenotypes, depending (probably) on exactly how the yeast to hyphal transition is affected. Furthermore, these phenotypes are accessible from each other - the cells don’t have to go back to the 100% yeast form in order to go from “star” to “hat.” The white-opaque transition is only found in a few strains and so far as I know no one has succeeded in inducing it with mutagenesis. Opaque cells contain antigens that are all their own, and there are only two phenotypes. Opaque cells have a peculiar surface, which is not well understood. We have mapped some “switching” genes for WO (the white-opaque switch) to the third chromosome; using spheroplast fusion and parasexual genetics we can show that loss of the homologues of this chromosome which come from the switching parent causes cells to lose the abilit

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