Susceptibility of intact germinating Arabidopsis thaliana to human fungal pathogens Cryptococcus neoformans and C. gattii

Appl Environ Microbiol. 2013 May;79(9):2979-88. doi: 10.1128/AEM.03697-12. Epub 2013 Feb 22.

Abstract

The fungus Cryptococcus contributes a large global burden of infectious death in both HIV-infected and healthy individuals. As Cryptococcus is an opportunistic pathogen, much of the evolutionary pressure shaping virulence occurs in environments in contact with plants and soil. The present studies investigated inoculation of intact seeds of the common weed Arabidopsis thaliana with fungal cells over a 21-day period. C. gattii was the more virulent plant pathogen, resulting in disrupted germination as well as increased stem lodging, fungal burden, and plant tissue colocalization. C. neoformans was a less virulent plant pathogen but exhibited prolonged tissue residence within the cuticle and vascular spaces. Arabidopsis mutants of the PRN1 gene, which is involved in abiotic and biotic signaling affecting phenylalanine-derived flavonoids, showed altered susceptibility to cryptoccocal infections, suggesting roles for this pathway in cryptococcal defense. The fungal virulence factor laccase was also implicated in plant pathogenesis, as a cryptococcal lac1Δ strain was less virulent than wild-type fungi and was unable to colonize seedlings. In conclusion, these studies expand knowledge concerning the ecological niche of Cryptococcus by demonstrating the pathogenic capacity of the anamorphic form of cryptococcal cells against healthy seedlings under physiologically relevant conditions. In addition, an important role of laccase in plant as well as human virulence may suggest mechanisms for laccase retention and optimization during evolution of this fungal pathogen.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / growth & development
  • Arabidopsis / immunology
  • Arabidopsis / microbiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cryptococcus gattii / enzymology
  • Cryptococcus gattii / genetics
  • Cryptococcus gattii / pathogenicity*
  • Cryptococcus neoformans / enzymology
  • Cryptococcus neoformans / genetics
  • Cryptococcus neoformans / pathogenicity*
  • Disease Susceptibility
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Germination
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Laccase / genetics
  • Laccase / metabolism*
  • Plant Diseases / immunology
  • Plant Diseases / microbiology*
  • Plant Leaves / growth & development
  • Plant Leaves / immunology
  • Plant Leaves / microbiology
  • Plant Stems / growth & development
  • Plant Stems / immunology
  • Plant Stems / microbiology
  • Seedlings / growth & development
  • Seedlings / immunology
  • Seedlings / microbiology
  • Seeds / growth & development
  • Seeds / immunology
  • Seeds / microbiology
  • Sequence Deletion
  • Virulence
  • Virulence Factors

Substances

  • Arabidopsis Proteins
  • Carrier Proteins
  • Fungal Proteins
  • Intracellular Signaling Peptides and Proteins
  • PRN protein, Arabidopsis
  • Virulence Factors
  • Laccase