Functional analysis of the superoxide dismutase family inAspergillus fumigatus

Abstract

SummaryReactive oxidant species produced by phagocytes have been reported as being involved in the killing of Aspergillus fumigatus. Fungal superoxide dismutases (SODs) that detoxify superoxide anions could be putative virulence factors for this opportunistic pathogen. Four genes encoding putative Sods have been identified in the A. fumigatus genome: a cytoplasmic Cu/ZnSOD (AfSod1p), a mitochondrial MnSOD (AfSod2p), a cytoplasmic MnSOD (AfSod3p) and AfSod4 displaying a MnSOD C-terminal domain. During growth, AfSOD1 and AfSOD2 were highly expressed in conidia whereas AfSOD3 was only strongly expressed in mycelium. AfSOD4 was weakly expressed compared with other SODs. The deletion of AfSOD4 was lethal. Dsod1 and Dsod2 mutants showed a growth inhibition at high temperature and a hypersensitivity to menadione whereas the sod3 mutant had only a slight growth delay at high temperature. Multiple mutations had only an additive effect on the phenotype. The triple sod1/sod2/sod3 mutant was characterized by a delay in conidial germination, a reduced conidial survival during storage overtime, the highest sensitivity to menadione and an increased sensitivity to killing by alveolar macrophage of immunocompetent mice. In spite of these phenotypes, no significant virulence difference was observed between the triple mutant and parental strain in experimental murine aspergillosis models in immunocompromised animals.

The MAP kinase MpkA controls cell wall integrity, oxidative stress response, gliotoxin production and iron adaptation in Aspergillus fumigatus

“…2A). Likewise, mitochondrial MnSOD (Asp f6), a hyphae‐specific metalloenzyme causing dismutation of the toxic superoxide anion (Schwienbacher et al ., 2005; Lambou et al ., 2010), had reduced transcript levels in Δ mpkA under standard conditions, whereas MnSOD showed an increased expression in the glucanex‐challenged Δ mpkA strain (Fig. 2A).…”

The Temporal Dynamics of Differential Gene Expression in Aspergillus fumigatus Interacting with Human Immature Dendritic Cells In Vitro

“…AfSOD3 (Aspf6) was up-regulated at all time points. It has been shown that A. fumigatus SOD enzymes are internal, cytoplasmic or mitochondrial, and may play a role in detoxification of fungal derived oxidants rather than having a role in detoxifying host derived reactive oxygen species [54]. An interesting observation was that no catalases were up-regulated and catA , spore-specific catalase, (AFUA_6g03890), was down-regulated during the interaction with iDC which was to be expected after germination.…”

“…However, pyomelanin production appears to be associated with cell wall stress rather than oxidative stress [58]. Increasingly there is evidence that non-oxidative mechanisms are employed by immune cells interacting with fungi [54] and the fungal cell wall would be a primary target. Melanin has a role in the structure and stability of the conidial cell wall [61] and it is conceivable that hyphal melanin may be involved in maintaining cell wall stability in response to stress.…”

Comparative functional analysis of the OCH1 mannosyltransferase families in Aspergillus fumigatus and Saccharomyces cerevisiae

“…Total RNA was isolated as previously described (Lambou et al , 2010). Plasmid DNA extraction was done by the Qiagen midi kit (Chatsworth, USA).…”

“…Primers used for all these constructions are reported in Table S1 (see Supporting information). A. fumigatus transformation experiments were achieved by electroporation of swollen conidia, using a protocol described previously (Lambou et al , 2010)…”