PGA4, a GAS homologue from Candida albicans, is up-regulated early in infection processes

Abstract Transglucosidases play a significant role in fungal cell wall biosynthesis. We identified three as yet undescribed genes encoding β-glucan transglucosidases, homologues of the pH-regulated PHR1 and PHR2 , in the genome of the pathogenic yeast Candida albicans . Transcript levels of the gene PGA4 encoding a putative GPI-anchored protein were elevated in C. albicans wild-type cells during infection of reconstituted human epithelial and mouse liver tissue, and transiently increased after induction of hyphal formation with serum. The serum-specific increase in PGA4 transcript was found to be dependent on the transcription factors Ras1p, Cyr1p, and Tec1p. The remaining C. albicans Phr homologues, PHR3 and PGA5 , showed low expression levels. Unlike PHR1 and PHR2 , the expression of PHR3 , PGA4 , and PGA5 was not dependent on the pH of the growth medium. Neither PHR3 deletion nor PGA4 disruption resulted in a distinct growth or morphology phenotype. A PGA4 disruption strain was found to have wild-type capacity of infecting reconstituted oral epithelial tissue. Our data suggest that PGA4 , and potentially PHR3 and PGA5 , are expressed under distinct conditions, which differ from those of PHR1 and PHR2 .