Complete mitochondrial genome sequence of a xerophilic fungus, Aspergillus pseudoglaucus.

Aspergillus pseudoglaucus is a xerophilic filamentous fungus which can produce various secondary metabolites. Here, we reported the complete mitochondrial genome sequence of A. pseudoglaucus isolated from Meju, a soybean brick in Korea. Its mitochondrial genome was successfully assembled from raw reads sequenced using MiSeq by Velvet and SOAPGapCloser. Total length of the mitochondrial genome is 53,882 bp, which is third longest among known Aspergillus mitochondrial genomes and encoded 58 genes (30 protein-coding genes including hypothetical ORFs, two rRNAs, and 26 tRNAs). Nucleotide sequence of coding regions takes over 66.6% and overall GC content is 27.8%. Phylogenetic trees present that A. pseudoglaucus is located outside of section Nidulantes. Additional researches will be required for clarifying phylogenetic position of section Aspergillus.

Characteristics of a Regulator of G-Protein Signaling (RGS) rgsC in Aspergillus fumigatus.

The regulator of G-protein signaling (RGS) proteins have a conserved RGS domain that facilitates the intrinsic GTPase activity of an activated Gα subunit of heterotrimeric G protein, thereby attenuating signal transduction. Among six predicted RGS proteins in the opportunistic human pathogenic fungus Aspergillus fumigatus, only three (FlbA, GprK, and Rax1) have been studied. The unexplored RgsC composed of the Phox-associated (PXA), RGS, Phox homology (PX), and Nexin_C superfamily domains is highly conserved in many ascomycete fungi, suggesting a crucial role of RgsC in fungal biology. To address this, we have investigated functions of the rgsC gene. The deletion (Δ) of rgsC causes impaired vegetative growth and asexual development coupled with reduced expression of key developmental regulators. Moreover, ΔrgsC results in accelerated and elevated conidial germination regardless of the presence or absence of an external carbon source. Furthermore, ΔrgsC causes reduced conidial tolerance to oxidative stress. In addition, activities and expression of catalases and superoxide dismutases (SODs) are severely decreased in the ΔrgsC mutant. The deletion of rgsC results in a slight reduction in conidial tolerance to cell wall damaging agents, yet significantly lowered mRNA levels of cell wall integrity/biogenesis transcription factors, indicating that RgsC may function in proper activation of cell wall stress response. The ΔrgsC mutant exhibits defective gliotoxin (GT) production and decreased virulence in the wax moth larvae, Galleria mellonella. Transcriptomic studies reveal that a majority of transporters is down-regulated by ΔrgsC and growth of the ΔrgsC mutant is reduced on inorganic and simple nitrogen medium, suggesting that RgsC may function in external nitrogen source sensing and/or transport. In summary, RgsC is necessary for proper growth, development, stress response, GT production, and external nutrients sensing.

Aspergillus fumigatus spore proteomics and genetics reveal that VeA represses DefA-mediated DNA damage response.

Aspergillus fumigatus reproduces and infects host by forming a high number of small asexual spores (conidia). The velvet proteins are global transcriptional regulators governing the complex process of conidiogenesis in this fungus. Here, to further understand the velvet-mediated regulation, we carried out comparative proteomic analyses of conidia of wild type (WT) and three velvet mutants (ΔveA, ΔvelB and ΔvosA). Cluster analysis of 184 protein spots showing at least 1.5-fold differential accumulation between WT and mutants reveal the clustering of WT- ΔveA and ΔvelB-ΔvosA. Among 43 proteins identified by Nano-LC-ESI-MS/MS, 23 including several heat shock proteins showed more than two-fold reduction in both the ∆velB and ∆vosA conidia. On the contrary, three proteins exhibited more than five-fold increase in ∆veA only, including the putative RNA polymerase II degradation factor DefA. The deletion of defA resulted in a reduced number of conidia and restricted colony growth. In addition, the defA deletion mutant conidia showed hypersensitivity against the DNA damaging agents NQO and MMS, while the ΔveA mutant conidia were more resistant against to NQO. Taken together, we propose that VeA controls protein level of DefA in conidia, which are dormant and equipped with multiple layers of protection against environmental cues.