SummaryChitin is an essential component of the fungal cell wall and its synthesis is under tight spatial and temporal regulation. The fungal human pathogen Candida albicans has a four member chitin synthase gene family comprising of CHS1 (class II), CHS2 (class I), CHS3 (class IV) and CHS8 (class I). LacZ reporters were fused to each CHS promoter to examine the transcriptional regulation of chitin synthesis. Each CHS promoter had a unique regulatory profile and responded to the addition of cell wall damaging agents, to mutations in specific CHS genes and exogenous Ca 2+. The regulation of both CHS gene expression and chitin synthesis was co-ordinated by the PKC, HOG MAP kinase and Ca 2+ /calcineurin signalling pathways. Activation of these pathways also resulted in increased chitin synthase activity in vitro and elevated cell wall chitin content. Combinations of treatments that activated multiple pathways resulted in synergistic increases in CHS expression and in cell wall chitin content. Therefore, at least three pathways co-ordinately regulate chitin synthesis and activation of chitin synthesis operates at both transcriptional and post-transcriptional levels.

Hydrophobins are small (ca. 100 amino acids) secreted fungal proteins that are characterized by the presence of eight conserved cysteine residues and by a typical hydropathy pattern. Class I hydrophobins self-assemble at hydrophilic-hydrophobic interfaces into highly insoluble amphipathic membranes, thereby changing the nature of surfaces. Hydrophobic surfaces become hydrophilic, while hydrophilic surfaces become hydrophobic. To see whether surface properties of assembled hydrophobins can be changed, 25 N-terminal residues of the mature SC3 hydrophobin were deleted (TrSC3). In addition, the cell-binding domain of fibronectin (RGD) was fused to the N terminus of mature SC3 (RGD-SC3) and TrSC3 (RGD-TrSC3). Self-assembly and surface activity were not affected by these modifications. However, physiochemical properties at the hydrophilic side of the assembled hydrophobin did change. This was demonstrated by a change in wettability and by enhanced growth of fibroblasts on Teflon-coated with RGD-SC3, TrSC3, or RGD-TrSC3 compared to bare Teflon or Teflon coated with SC3. Thus, engineered hydrophobins can be used to functionalize surfaces.Hydrophobins are moderately hydrophobic proteins secreted by fungi. They are characterized by the presence of eight cysteine residues in conserved spacing and by similar hydropathy patterns (30,32,34). Hydrophobins fulfill a broad spectrum of functions. They mediate escape of hyphae from a hydrophilic environment (41) and are involved in the formation of hydrophobic aerial structures such as aerial hyphae (4,23,28,36,38), spores (2,3,10,21,22), and fruiting bodies (5, 13). Moreover, they provide gas channels in fruiting bodies and lichens with a hydrophobic layer, which probably provides for more efficient gas exchange under wet conditions (14,16,27,29,31). Hydrophobins are also involved in the attachment of hyphae to hydrophobic surfaces (27, 37) and in the sensing thereof (22), which are important initial steps of pathogenic interactions before penetration and infection of the host can occur.The basidiomycete Schizophyllum commune contains at least four class I hydrophobin genes: SC1, SC3, SC4, and SC6 (6,11,17,33). SC3 is the best-characterized class I hydrophobin. It is involved in the formation of aerial hyphae (28,36,38,41) and in the attachment of hyphae to hydrophobic surfaces (37). Upon contact with hydrophilic-hydrophobic interfaces SC3 monomers self-assemble into a highly insoluble amphipathic membrane (36,37,40). This is accompanied with an increase in ␤-sheet structure at the water-air interface and by increase in ␣-helical structure at the water-hydrophobic solid interface (6). The latter form is an intermediate to the form with increased ␤-sheet structure (35). Upon self-assembly of SC3 at the waterair interface the water surface tension is reduced to as low as 24 mJ m Ϫ2 , which makes assembled SC3 one of the most powerful biosurfactants known to date (26,41). When a hydrophobic solid is incubated in an aqueous hydrophobin solution, an amphipathic membrane of the protein...