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Transcriptome analysis of the Aspergillus fumigatus calcineurin

ABSTRACT: Calcineurin plays an important role in the control of cell morphology and virulence in fungi. Calcineurin is a serine/threonine-specific protein phosphatase heterodimer consisting of a catalytic subunit A and a regulatory Ca2+/Calmodulin binding subunit. A mutant of A. fumigatus lacking the calcineurin A (calA) catalytic subunit exhibited defective hyphal morphology related to apical extension and branching growth, which resulted in drastically decreased filamentation. Here, we investigated which pathways are influenced by A. fumigatus calcineurin during proliferation by comparatively determining the transcriptional profile of A. fumigatus wild type and delta calA mutant strains. Our results showed that although the mitochondrial function is reduced in the delta calA mutant strain, its respiratory chain is functional and the mutant has increased alternative oxidase (aoxA) mRNA accumulation and activity. Furthermore, we identified several genes that encode transcription factors that have increased mRNA expression in the delta calA mutant and that could be involved in the Cal-CrzA pathway. Deletion mutants for these transcription factors had also reduced susceptibility to itraconazole, caspofungin, and sodium dodcyl sulfate.

ORGANISM(S): Aspergillus fumigatus

PROVIDER: GSE13939 | GEO | 2008/12/23

SECONDARY ACCESSION(S): PRJNA110277

REPOSITORIES: GEO

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Project description:Calcineurin plays an important role in the control of cell morphology and virulence in fungi. Calcineurin is a serine/threonine-specific protein phosphatase heterodimer consisting of a catalytic subunit A and a regulatory Ca2+/Calmodulin binding subunit. A mutant of A. fumigatus lacking the calcineurin A (calA) catalytic subunit exhibited defective hyphal morphology related to apical extension and branching growth, which resulted in drastically decreased filamentation. Here, we investigated which pathways are influenced by A. fumigatus calcineurin during proliferation by comparatively determining the transcriptional profile of A. fumigatus wild type and delta calA mutant strains. Our results showed that although the mitochondrial function is reduced in the delta calA mutant strain, its respiratory chain is functional and the mutant has increased alternative oxidase (aoxA) mRNA accumulation and activity. Furthermore, we identified several genes that encode transcription factors that have increased mRNA expression in the delta calA mutant and that could be involved in the Cal-CrzA pathway. Deletion mutants for these transcription factors had also reduced susceptibility to itraconazole, caspofungin, and sodium dodcyl sulfate. For the time course microarray experiments, 1.0 x 109 conidia of both A. fumigatus wild type [CEA17 delta akuB(KU80)] and mutant strain (delta calA) were used to inoculate 400 ml of pre-warmed liquid cultures in complete medium (YG) in 1 L erlenmeyer flasks. Cultures were allowed to grow for 6, 8, 12, 18 and 24 hours in a reciprocal shaker (250 rpm) at 37°C. At each time point, germilings were harvested by centrifugation or filtration and total RNA was extracted. Hybridization experiments were competitive using Cy3 or Cy5-labeled probes derived from both wild type and delta calA strain grown for 6, 8, 12, 18 and 24 hours. Hybridizations were performed using the wild type RNA as reference in comparison to the mutant strain (test RNA) for the same time point. Normalized signal intensities were used to generate relative hybridization ratios (query/reference). Following normalization, the values for each gene in-slide replicates were condensed (median variance <0.01), and corresponding flip-dye replicates were averaged to compensate for dye-specific effects (see Supplementary files linked below).

Project description:CRZ is a C2H2 zinc finger transcription factor activated by calcineurin, a protein phosphatase activated by calcium-calmodulin, in different stress conditions related with calcium cell accumulation. CRZ binds to a specific element on the promoter region of genes called CDRE (calcineurin-dependent response element) shown to be sufficient for calcium- and calcineurin-dependent gene expression. In order to investigate which pathways are involved under calcium stress conditions, we determined the transcriptional profile of A. fumigatus delta crzA mutant strain upon a time course 200 mM calcium chloride treatment. Conidia from the mutant and wild type strains were incubated at 37Â°C in complete medium for 16 hours and were challenged with 200 mM calcium chloride for 10 and 30 minutes. At each time point, the mycelia were harvested by centrifugation and used for competitive microarray hybridizations. We were able to observe a decreased mRNA expression of genes encoding inorganic ion transport proteins and lipid transport. In contrast, increased mRNA expression was observed for several genes involved in transcription, energy production and conversion, cell cycle control, cell division, chromosome partitioning, amino acid, lipid and carbohydrate transport and metabolism, nucleotide transport, cell wall and membrane biogenesis, posttranslation modifications, protein turnover, chaperones, inorganic ion transport, signal transduction mechanisms, intracellular trafficking, secretion and vesicular transport. Keywords: gene expression array-based (log2 ratio) For the time course microarray experiments, 5.0 x 108 conidia of A. fumigatus wild type [CEA17 delta akuB(KU80)] and delta crzA strains were inoculated in 300 ml of pre-warmed liquid cultures (YG) in 500-mL erlenmeyer flasks and allowed to grow for 16 hours in a reciprocal shaker (250 rpm) at 37Â°C. After this time, the cultures were added by calcium chloride (200 mM) and incubated for 10 and 30 more minutes before mycelia recovery and RNA extraction. Hybridization experiments were competitive using probes derived from calcium chloride shock cultures using the wild type strain exposed to calcium (10 or 30 minutes) as the reference RNA for every hybridizantion. Normalized signal intensities were used to generate relative hybridization ratios (query/reference). Following normalization, the values for each gene's in-slide replicates were averaged (median variance <0.01), and corresponding flip-dye replicates were averaged to compensate for dye-specific effects. These final, processed data are linked below as supplementary files.

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Transcriptome analysis of the Aspergillus fumigatus calcineurin

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