Transcription Factor SomA Is Required for Adhesion, Development and Virulence of the Human Pathogen Aspergillus fumigatus

PLoS Pathog. 2015 Nov 3;11(11):e1005205. doi: 10.1371/journal.ppat.1005205. eCollection 2015.

Abstract

The transcription factor Flo8/Som1 controls filamentous growth in Saccharomyces cerevisiae and virulence in the plant pathogen Magnaporthe oryzae. Flo8/Som1 includes a characteristic N-terminal LUG/LUH-Flo8-single-stranded DNA binding (LUFS) domain and is activated by the cAMP dependent protein kinase A signaling pathway. Heterologous SomA from Aspergillus fumigatus rescued in yeast flo8 mutant strains several phenotypes including adhesion or flocculation in haploids and pseudohyphal growth in diploids, respectively. A. fumigatus SomA acts similarly to yeast Flo8 on the promoter of FLO11 fused with reporter gene (LacZ) in S. cerevisiae. FLO11 expression in yeast requires an activator complex including Flo8 and Mfg1. Furthermore, SomA physically interacts with PtaB, which is related to yeast Mfg1. Loss of the somA gene in A. fumigatus resulted in a slow growth phenotype and a block in asexual development. Only aerial hyphae without further differentiation could be formed. The deletion phenotype was verified by a conditional expression of somA using the inducible Tet-on system. A adherence assay with the conditional somA expression strain indicated that SomA is required for biofilm formation. A ptaB deletion strain showed a similar phenotype supporting that the SomA/PtaB complex controls A. fumigatus biofilm formation. Transcriptional analysis showed that SomA regulates expression of genes for several transcription factors which control conidiation or adhesion of A. fumigatus. Infection assays with fertilized chicken eggs as well as with mice revealed that SomA is required for pathogenicity. These data corroborate a complex control function of SomA acting as a central factor of the transcriptional network, which connects adhesion, spore formation and virulence in the opportunistic human pathogen A. fumigatus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / metabolism*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / physiology*
  • Humans
  • Hyphae / genetics
  • Magnaporthe / metabolism
  • Magnaporthe / pathogenicity*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Signal Transduction / genetics
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Virulence

Substances

  • Fungal Proteins
  • Transcription Factors

Grants and funding

GHB was supported by the Deutsche Forschungsgemeinschaft FOR1334 (http://gepris.dfg.de/gepris/projekt/140043741), the Federal Ministry of Education and Research (BMBF) BioFung project and the Eranet PathoGenoMics TRANSPAT (https://www.pathogenomics-era.net/FundedProjects). TH was supported by the Deutsche Forschungsgemeinschaft CRC/Transregio 124 "Human-pathogenic fungi and their human host - Networks of interaction - FungiNet" (www.funginet.de). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.