Superoxide radical is involved in the sclerotial differentiation of filamentous phytopathogenic fungi: identification of a fungal xanthine oxidase

Fungal Biol. May-Jun 2010;114(5-6):387-95. doi: 10.1016/j.funbio.2010.01.010. Epub 2010 Mar 11.


This study shows that the direct indicator of oxidative stress superoxide radical (O·₂⁻) is involved in the sclerotial differentiation of the phytopathogenic filamentous fungi Rhizoctonia solani, Sclerotinia sclerotiorum, Sclerotium rolfsii, and Sclerotinia minor. The production rate of O·₂⁻ and the antioxidant enzyme superoxide dismutase (SOD) levels in the sclerotiogenic fungi were significantly higher and lower, respectively, than those of their non-differentiating counterpart strains, which strongly suggests that the oxidative stress of the sclerotium differentiating fungi is higher than that of the non-differentiating ones. Xanthine oxidase (XO), which was detected for the first time in fungi in general, was localized in the cytoplasmic membrane. The contribution of XO in the overall O·₂⁻production was very significant, reaching 30-70% among the strains, especially in the transition developmental stage between the undifferentiated and the differentiated state, suggesting a sclerotium triggering and a phytopathogenic role of XO during plant infection. The additional finding that these fungi secrete extracellular SOD can be related to their protection from the response of plants to produce O·₂⁻ at infection sites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascomycota / enzymology*
  • Ascomycota / genetics
  • Ascomycota / growth & development*
  • Ascomycota / metabolism
  • Cytoplasm / enzymology
  • Cytoplasm / genetics
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Oxidative Stress
  • Plant Diseases / microbiology
  • Protein Transport
  • Superoxides / metabolism*
  • Xanthine Oxidase / genetics
  • Xanthine Oxidase / metabolism*


  • Fungal Proteins
  • Superoxides
  • Xanthine Oxidase