HapX Mediates Iron Homeostasis in the Pathogenic Dermatophyte Arthroderma benhamiae but Is Dispensable for Virulence

PLoS One. 2016 Mar 9;11(3):e0150701. doi: 10.1371/journal.pone.0150701. eCollection 2016.

Abstract

For many pathogenic fungi, siderophore-mediated iron acquisition is essential for virulence. The process of siderophore production and further mechanisms to adapt to iron limitation are strictly controlled in fungi to maintain iron homeostasis. Here we demonstrate that the human pathogenic dermatophyte Arthroderma benhamiae produces the hydroxamate siderophores ferricrocin and ferrichrome C. Additionally, we show that the iron regulator HapX is crucial for the adaptation to iron starvation and iron excess, but is dispensable for virulence of A. benhamiae. Deletion of hapX caused downregulation of siderophore biosynthesis genes leading to a decreased production of siderophores during iron starvation. Furthermore, HapX was required for transcriptional repression of genes involved in iron-dependent pathways during iron-depleted conditions. Additionally, the ΔhapX mutant of A. benhamiae was sensitive to high-iron concentrations indicating that HapX also contributes to iron detoxification. In contrast to other pathogenic fungi, HapX of A. benhamiae was redundant for virulence and a ΔhapX mutant was still able to infect keratinized host tissues in vitro. Our findings underline the highly conserved role of the transcription factor HapX for maintaining iron homeostasis in ascomycetous fungi but, unlike in many other human and plant pathogenic fungi, HapX of A. benhamiae is not a virulence determinant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arthrodermataceae / genetics
  • Arthrodermataceae / growth & development
  • Arthrodermataceae / pathogenicity*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / drug effects
  • Genes, Fungal
  • Homeostasis* / drug effects
  • Homeostasis* / genetics
  • Humans
  • Hyphae / drug effects
  • Hyphae / physiology
  • Iron / metabolism*
  • Iron / pharmacology
  • Keratins / pharmacology
  • Mutation / genetics
  • Pigmentation / drug effects
  • Sequence Homology, Amino Acid
  • Siderophores / metabolism
  • Spores, Fungal / drug effects
  • Spores, Fungal / physiology
  • Virulence / drug effects
  • Virulence / genetics

Substances

  • Fungal Proteins
  • Siderophores
  • Keratins
  • Iron

Grants and funding

This work was supported by the DFG funded excellence graduate school Jena School for Microbial Communication (JSMC; GSC 214; www.jsmc.uni-jena.de) and the Leibniz Institute for Natural Product Research and Infection Biology (www.leibniz-hki.de). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.