TRANSCRIPTOME ANALYSIS OF THE ASPERGILLUS FUMIGATUS CALCINEURIN MUTANT

Iran Malavazi (UFSCar); Márcia Eliana da Silva Ferreira (FCFRP-USP); Frederico Marianetti Soriani (FCFRP-USP); Taísa Magnani Dinamarco (FCFRP-USP); Marcela Savoldi (FCFRP-USP); Sérgio Akira Uyemura (FCFRP-USP); Maria Helena de Souza Goldman (FCFRP-USP); Gustavo Henrique Goldman (FCFRP-USP)

Calcineurin plays an important role in the control of cell morphology and virulence in fungi. Calcineurin is a serine/threonine-specific phosphatase  heterodimer consisting of a catalytic subunit A and a regulatory Ca²⁺/Calmodulin binding subunit B. The association of the two subunits is essential for activity. 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 DcalA mutant strains during growth in complete medium in a time-course experiment. Our results showed that although the mitochondrial function is reduced in the DcalA mutant strain, its respiratory chain is functional. The mutant has increased alternative oxidase (aoxA) mRNA accumulation (determined by real time RT PCR) and activity determined by measuring the oxygen uptake in germlings from both wild type and DcalA strains using a Clark type electrode. Also, the mitochondrial copy number is reduced in the DcalA mutant strain. Furthermore, we identified several genes that encode transcription factors that have increased mRNA expression in the DcalA mutant and that could be potentially involved in the CalA-CrzA pathway. Deletion mutants for these transcription factors had also reduced susceptibility to itraconazole, caspofungin, and sodium dodecyl sulfate. Our study provides evidences for several pathways that are dependent on calcineurin–CrzA and that could be responsible for the observed decreased virulence in the DcalA strain. These findings open exciting new possibilities for research into environmental sensing and nutrient acquisition in A. fumigatus.