It remains to be experimentally determined if these sequences are really important for AfCrzA gene regulation, both for gene induction and repression. Prior to this work, a study analysing global gene expression regulated by the calcineurin/Crz1p signaling pathway in S. cerevisiae had attempted to identify genes regulated by calcium and sodium [30]. Calcineurin activation induced 153 genes involved in cell wall biosynthesis, ion homeostasis, vesicle trafficking, lipid synthesis, and protein degradation. A notable similarity was observed by the BMN673 authors in the gene expression patterns of FK506-treated cells and crz1 cells, suggesting

that Crz1p is required Trametinib research buy for most calcineurin-dependent changes in gene expression. Recently, Soriani et al. [16] opted to an alternative strategy, exposing A. fumigatus wild type strain to a short pulse with a high concentration of calcium, and arbitrarily choosing several genes that were less or more expressed in the microarray hybridization analyses to verify their expression in the wild type, and ΔAfcalA and ΔAfcrzA mutant strains by real-time RT-PCR. Thus, these authors were able to determine if the expression of these genes was dependent on calcineurin and/or AfCrzA. They verified that the majority of these genes suffered blocking

of mRNA accumulation in the ΔAfcrzA background. The results shown here added more information about the transcriptional network involved in the calcineurin-AfCrzA in response to calcium. Construction of Aspergilli CrzA overexpression strains Overexpression of AfCrzA could reveal genes regulated by the calcineurin-AfCrzA pathway. Accordingly, we constructed an overexpression A. fumigatus AfCrzA strain by using the alcA promoter. The A. nidulans alcA promoter homologously replaced the AfcrzA promoter (for details of the PAK5 construction, see Methods section). The alcA promoter is repressed by glucose, derepressed by glycerol

and induced to high levels by ethanol or L-threonine [32]. When A. fumigatus is grown on glycerol 2% supplemented either with ethanol 2% or threonine 100 mM, AfcrzA mRNA accumulation in increased about 3.8- and 3.6-times, respectively compared to growth on glucose 4% (Figure 2A, left and right graphs). As expected, when the AfcrzA is repressed in the presence of glucose, the alcA::AfcrzA strain is more sensitive to calcium (Figure 2B); however, surprisingly high levels of AfCrzA mRNA accumulation also make the alcA::AfcrzA strain more calcium-sensitive (Figure 2B). These results suggest that CrzA overexpression could potentially disturb the mRNA accumulation of genes that are important for the calcium homeostasis in the cell, thus disturbing the calcium metabolism into the cell and consequently the growth in the presence of increasing calcium concentrations.