A complementation analysis by parasexual recombination of Candida albicans morphological mutants.

Benomyl treatment (at 100 micrograms ml-1) of Candida albicans 1001, and other strains derived from it, determined the appearance of morphological mutants similar to those derived from UV irradiation treatment. A permanent alteration in the morphogenesis of these mutant strains determined their inability to grow by budding, to form oval yeast cells or blastospores (Y-phenotype) and their growth as long filamentous forms, mostly with the appearance of pseudomycelium, giving rise to rough colonies (R phenotype). In order to carry out a genetic complementation analysis, we isolated morphological mutants that carried other genetic markers (nutritional, conditional lethal) adequate for crosses by means of protoplast fusion. Wild-type hybrids of regular mononuclear oval yeast cells and smooth colonies were obtained by crossing pairs of complementing mutants, whereas hybrids from crosses of non-complementing mutants still retained their morphological alterations. Our results define two complementation groups, which represent two genes relevant for dimorphism, whose alteration interferes with the correct transition from blastospores to mycelium.