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A more recent version of this article appeared on March 1, 2008 Originally published as MBC in Press, 10.1091/mbc.E07-07-0688 on January 2, 2008
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Submitted on July 20, 2007
Revised on November 28, 2007
Accepted on December 17, 2007
Department of Biology, The University of Iowa, Iowa City, IA 52242
Monitoring Editor: Patrick Brennwald
Candida albicans must undergo a switch from white to opaque to mate. Opaque cells then release mating type-specific pheromones which induce mating responses in opaque cells. Uniquely in C. albicans, the same pheromones induce mating-incompetent white cells to become cohesive, form an adhesive basal layer of cells on a surface and then generate a thicker biofilm which, in vitro, facilitates mating between minority opaque cells. Through mutant analysis, it is demonstrated that the pathways regulating the white and opaque cell responses to the same pheromone share the same upstream components, including receptors, heterotrimeric G-protein and MAP kinase cascade, but use different downstream transcription factors that regulate the expression of genes specific to the alternative responses. This configuration, while common in higher, multicellular systems, is not common in fungi, and has not been reported in S. cerevisiae. The implications in the evolution of multicellularity in higher eukaryotes are discussed.