Epigenetic Switching in the Human Fungal Pathogen Candida albicans

Abstract

The human fungal pathogen Candida albicans can grow in a number of distinct morphologies: yeast (including white, gray, opaque, and GUT forms), hyphae, and pseudohyphae. White and opaque cells are two heritable cell types. Despite the differences in several biological aspects including cellular and colony appearances, global gene profiles, virulence, filamentation, mating competency, and susceptibility to antifungals, white and opaque cells contain the same set of genomic DNA. The regulation of white–opaque switching is at the epigenetic level. Although the switch between the white and opaque phenotypes can occur spontaneously at low frequency, it can also be induced by certain environmental cues such as host-related signaling molecules like CO2 and N-acetylglucosamine (GlcNAc). In this chapter, we will review the environmental and genetic regulatory mechanisms of this epigenetic switch in C. albicans. The relationships between white–opaque switching and pathogenesis, sexual reproduction, and other biological processes will be discussed. The newly discovered white–gray–opaque tristable switching system and white–opaque switching in two C. albicans-related species, Candida dubliniensis and Candida tropicalis, will be included in the last two sections. These morphological switches may provide Candida species with a better ability to adapt to the changing host environment and survive under diverse niches.