Identification of possible targets of the Aspergillus fumigatus CRZ1 homologue, CrzA

Abstract

BackgroundCalcineurin, a serine/threonine-specific protein phosphatase, plays an important role in the control of cell morphology and virulence in fungi. Calcineurin regulates localization and activity of a transcription factor called CRZ1. Recently, we characterize Aspergillus fumigatus CRZ1 homologue, AfCrzA. Here, we investigate which pathways are influenced by A. fumigatus AfCrzA during a short pulse of calcium by comparatively determining the transcriptional profile of A. fumigatus wild type and ΔAfcrzA mutant strains.ResultsWe were able to observe 3,622 genes modulated in at least one timepoint in the mutant when compared to the wild type strain (3,211 and 411 at 10 and 30 minutes, respectively). Decreased mRNA abundance in the ΔcrzA was seen for genes encoding calcium transporters, transcription factors and genes that could be directly or indirectly involved in calcium metabolism. Increased mRNA accumulation was observed for some genes encoding proteins involved in stress response. AfCrzA overexpression in A. fumigatus increases the expression of several of these genes. The deleted strain of one of these genes, AfRcnA, belonging to a class of endogenous calcineurin regulators, calcipressins, had more calcineurin activity after exposure to calcium and was less sensitive to menadione 30 μM, hydrogen peroxide 2.5 mM, EGTA 25 mM, and MnCl2 25 mM. We constructed deletion, overexpression, and GFP fusion protein for the closely related A. nidulans AnRcnA. GFP::RcnA was mostly detected along the germling, did not accumulate in the nuclei and its location is not affected by the cellular response to calcium chloride.ConclusionWe have performed a transcriptional profiling analysis of the A. fumigatus ΔAfcrzA mutant strain exposed to calcium stress. This provided an excellent opportunity to identify genes and pathways that are under the influence of AfCrzA. AfRcnA, one of these selected genes, encodes a modulator of calcineurin activity. Concomitantly with A. fumigatus AfrcnA molecular analysis, we decided to exploit the conserved features of A. nidulans calcineurin system and investigated the A. nidulans AnRcnA homologue. A. nidulans AnRcnA mutation is suppressing CnaA mutation and it is responsible for modulating the calcineurin activity and mRNA accumulation of genes encoding calcium transporters.

Calcium signaling components in the human pathogenCryptococcus neoformans

“…[14][15][16][17][18][19][20] The zinc finger transcription factor Crz1 is the molecular target of calcineurin, that mediates nuclear translocation of Crz1 after dephosphorylation. 19 Orthologs of S. cerevisiae Crz1 are involved in virulence and pathogenesis in several plant and human fungal pathogens, such as Magnaporthe oryzae, Botrytis cinerea, A. fumigatus and Candida glabrata.…”

Calcineurin-Crz1 Signaling in Lower Eukaryotes

“…Interestingly, it has been shown that calcineurin regulates the transcription of chitin synthases in response to caspofungin treatment in A. fumigatus (62). However, CrzA seems to play only a minor role in this process: in the transcriptional profiles, only chitin synthase A (chsA) was misregulated in response to Ca 2ϩ treatment (61). Additionally, Cramer et al showed that calcineurin but not CrzA is involved in the regulation of ␤-1,3-glucan biosynthesis genes in A. fumigatus (18).…”

“…Transcriptional profiling of a ⌬crz1 strain in Cryptococcus neoformans under conditions of nutrient limitation revealed 208 downregulated genes compared to the wild type (60). In Aspergillus nidulans, 25 genes were induced under calcium stress conditions in a ⌬crzA strain (24), and in A. fumigatus, Soriani et al identified between 400 and 3,200 genes (depending on the length of the Ca 2ϩ pulse) whose expression is CrzA dependent (61). In both Aspergillus studies, putative CDREs were identified in the promoter regions of CrzA-dependent genes.…”

The role of three calcineurin subunits and a related transcription factor (Crz1) in conidiation, multistress tolerance and virulence in Beauveria bassiana

“…Upon activation by increased Ca 2+ in the cytosol, CN dephosphorylates Crz1 and the dephosphorylated Crz1 is then transferred to the nucleus from the cytosol for the regulation of target gene expression (Santos and de Larrinoa 2005;Soriani et al 2008;Kim et al 2010). In A. fumigatus, a Crzl homologue was shown to activate many stress-responsive genes, such as those encoding class V chitinase, multidrug-resistance proteins and heat-shock protein Scf1, at increased Ca 2+ levels (Soriani et al 2010). Deletion of the Crz1 gene in Magnaporthe oryzae caused phenotypic changes in vegetative growth, sporulation, conidial viability, pathogenicity and stress tolerance (Zhang et al 2009).…”