Abstract
Author SummaryPhenotypic transitions enable fungal pathogens to better adapt to their ever-changing environments. Approximately 10% of natural Candida albicans strains, which are homozygous at the mating type locus (MTL, a/a and α/α), can switch between two distinguishable morphological forms: white and opaque. The two cell types differ in a number of biological aspects including virulence, susceptibility to host immune attacks, and mating competency. Here, we demonstrate that white-opaque switching competency is not restricted to the MTL homozygous strains, but is a general characteristic of all MTL strain types of C. albicans (a/a, α/α, and a/α). Two host environmental cues, N-acetylglucosamine and CO2, promote white-to-opaque switching and stabilize the opaque phenotype. Thus, although switching is normally blocked in a/α cells, this block can be overcome through specific environmental changes. We further show that three transcriptional regulators (Rfg1, Brg1, and Efg1) help to regulate white-opaque switching in MTL heterozygotes of C. albicans. This study generalizes white-opaque switching to strains with all mating-type configurations and emphasizes its importance in host adaptation, pathogenesis, and parasexual reproduction.
Highlights
Phenotypic plasticity is critical for microorganisms to survive under fluctuating environments
10% of natural Candida albicans strains, which are homozygous at the mating type locus (MTL, a/a and a/ a), can switch between two distinguishable morphological forms: white and opaque
We demonstrate that white-opaque switching competency is not restricted to the mating type-like (MTL) homozygous strains, but is a general characteristic of all MTL strain types of C. albicans (a/a, a/a, and a/a)
Summary
Phenotypic plasticity is critical for microorganisms to survive under fluctuating environments. Phenotypic switching is a common strategy to rapidly adapt to different host niches and facilitate colonization and infection [1]. A specific phenotype can confer the fungus a growth advantage over competing microorganisms in a specific environment or host niche. The major causative agent of fungal infections in humans, can switch between two different visible cell types: white and opaque [2]. The two cell types differ in a number of biological aspects including morphology, virulence, and mating competence [3,4,5]. It has recently been shown that Candida tropicalis, another important human fungal pathogen, can undergo whiteopaque switching and parasexual mating [11,12]
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