A GAS-like gene family in the pathogenic fungus Candida glabrata

In fungi, the cell wall plays a major role in host-pathogen interactions. D espite this, little is known about the molecular basis of cell wall assembl y in Candida glabrata, which has emerged as the second most common cause of systemic candidosis. A C. glabrata gene family, CgGAS1-3, that shares sign ificant homologies with both the GAS1 gene of Saccharomyces cerevisiae, whi ch is necessary for cell wall assembly, and the pH-regulated genes PHR1 and PHR2 of Candida albicans, which are involved in cell wall assembly and req uired for virulence, has been cloned. Among the members of this family, CgG AS1-3 display a unique expression pattern. Both CgGAS1 and CgGAS2 are const itutively expressed. In contrast, CgGAS3 transcript was not detectable unde r any of the assayed conditions. The C. glabrata actin gene, CgACT1, has al so been cloned to be used as a meaningful loading control in Northern blots . CgGAS1 and CgGAS2 were deleted by two different methodological approaches . A rapid PCR-based strategy by which gene disruption was achieved with sho rt regions of homology (50 bp) was applied successfully to C. glabrata. Del ta Cggas1 or Delta Cggas2 cells demonstrated similar aberrant morphologies, displaying an altered bud morphology and forming floccose aggregates. Thes e phenotypes suggest a role for CgGAS1 and CgGAS2 in cell wall biosynthesis . Further evidence for this hypothesis was obtained by successful functiona l complementation of a gas1 null mutation in S. cerevisiae with the C. glab rata CgGAS1 or CgGAS2 gene.