Convergent Regulation of Candida albicans Aft2 and Czf1 in Invasive and Opaque Filamentation

Abstract

Candida albicans is the most common fungal pathogen of mucosal infections and invasive diseases in immuno-compromised humans. The abilities of yeast-hyphal growth and white-opaque switching affect C. albicans physiology and virulence. Here, we showed that C. albicans Aft2 regulator was required for embedded filamentous growth and opaque cell-type formation. Under low-temperature matrix embedded conditions, Aft2 functioned downstream of Czf1-mediated pathway and was required for invasive filamentation. Moreover, deletion of AFT2 significantly reduced opaque cell-type formation under N-acetylglucosamine (GlcNAc) inducing conditions. Ectopic expression of CZF1 slightly increased the white-opaque switching frequency in the aft2Δ/Δ mutant, but did not completely restore to wild-type levels, suggesting that Czf1 at least partially bypassed the essential requirement for Aft2 in response to opaque-inducing cues. In addition, multiple environmental cues altered AFT2 mRNA and protein levels, such as low temperature, physical environment and GlcNAc. Although the absence of Czf1 or Efg1 also increased the expression level of AFT2 gene, deletion of CZF1 remarkably reduced the stability of Aft2 protein. Furthermore, C. albicans Aft2 physically interacted with Czf1 under all tested conditions, whereas the interaction between Aft2 and Efg1 was barely detectable under embedded conditions, supporting the hypothesis that Aft2, together with Czf1, contributed to activate filamentous growth by antagonizing Efg1-mediated repression under matrix-embedded conditions.

Phenotypic Profiling Reveals that Candida albicans Opaque Cells Represent a Metabolically Specialized Cell State Compared to Default White Cells

“…Thus, many of the same metabolic cues impact both phenotypic switching and filamentation. This observation is likely the direct result of white-opaque switching and filamentous growth sharing transcriptional regulators (44, 77, 83–86). …”

The glycerophosphocholine acyltransferase Gpc1 contributes to phosphatidylcholine biosynthesis, long-term viability, and embedded hyphal growth in Candida albicans

“…Hyphal growth is regulated by several complex signaling pathways including the Cek1 MAPK, cAMP-PKA, pH response, Hog1 MAPK, and the Tup1-mediated negative regulatory pathways ( 35 ). However, in embedded conditions at 25 °C, C. albicans produces hyphae in a process involving the transcription factor Czf1 ( 36 , 37 ). Czf1 regulation of hyphal growth in embedded conditions varies uniquely from other hyphal growth triggers ( 35 , 37 ).…”

“…However, in embedded conditions at 25 °C, C. albicans produces hyphae in a process involving the transcription factor Czf1 ( 36 , 37 ). Czf1 regulation of hyphal growth in embedded conditions varies uniquely from other hyphal growth triggers ( 35 , 37 ). We did not detect any defects in filamentous growth in the gpc1 Δ/Δ strain when grown on spider medium or in the presence of serum.…”

Binding Sites in theEFG1Promoter for Transcription Factors in a Proposed Regulatory Network: A Functional Analysis in the White and Opaque Phases ofCandida albicans

“…In addition, deletion of WOR2 ( orf19.5992 ) had no effect on N-acetylglucosamine-induced switching from white to opaque ( Tong et al 2014 ). Overexpressing CZF1 ( orf19.3127 ) or WOR3 ( orf19.467 ) caused an increase in the frequency of switching from white to opaque, and both increases were dependent on WOR1 ( orf19.4884 ) ( Vinces and Kumamoto 2007 ; Lohse et al 2013 ; Xu et al 2015 ). Overexpression of AHR1 ( orf19.7381 ) caused an increase in the frequency of opaque to white switching, and the increase in this case was dependent on EFG1 ( orf19.610 ) ( Wang et al 2011 ).…”