Involvement of OS-2 MAP kinase in regulation of the large-subunit catalases CAT-1 and CAT-3 in Neurospora crassa

Genes Genet Syst. 2007 Aug;82(4):301-10. doi: 10.1266/ggs.82.301.

Abstract

Neurospora crassa has four catalase genes--cat-1, cat-2, cat-3, and ctt-1/cat-4. cat-1 and cat-3 encode two fungal-specific large-subunit catalases CAT-1 and CAT-3 normally produced in conidia and growing hyphae, respectively. cat-2 encodes CAT-2 catalase-peroxidase normally produced in conidia. ctt-1 (or cat-4), of which expression was controlled by OS-2 MAP kinase (Noguchi et al., Fungal Genet. Biol. 44, 208-218), encodes a small-subunit catalase with unknown function. To clarify the contribution of OS-2 on the regulation of CAT-1, CAT-2, and CAT-3, we performed quantitative RT-PCR and in-gel catalase activity analyses. When the hyphae were treated with a fungicide (1 mug/ml fludioxonil) or subjected to an osmotic stress (1 M sorbitol), cat-1 was strongly upregulated and CAT-1 was reasonably induced in the wild-type strain. Interestingly, fludioxonil caused not only the CAT-1 induction but also a remarkable CAT-3 decrease in the wild-type hyphae, implying of an abnormal stimulation of asexual differentiation. These responses were not observed in an os-2 mutant hyphae, indicating an involvement of OS-2 in the cat-1 expression; however, os-2 was dispensable for the production of CAT-1 in conidia. In contrast, the expression of cat-2 was significantly induced by heat shock (45 degrees C) and that of cat-3 was moderately stimulated by an oxidative stress (50 microg/ml methyl viologen) in both the wild-type strain and the os-2 mutant, and corresponding enzyme activities were detected after the treatments. Although basal levels of transcription of cat-1 and cat-3 in an os-2 mutant hyphae were a few-fold lower than in the wild-type hyphae, the os-2 mutant exhibited a considerably lower levels of CAT-3 activity than the wild-type strain. These findings suggest that OS-2 MAP kinase regulated the expression of cat-1 and cat-3 transcriptionally, and probably that of cat-3 posttranscriptionally, even though the presence of another regulatory system for each of these two genes is evident.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalase / genetics*
  • Catalase / metabolism
  • Dioxoles / pharmacology
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Enzymologic*
  • Gene Expression Regulation, Fungal
  • Hydrogen Peroxide / pharmacology
  • Hyphae / genetics
  • Hyphae / metabolism
  • Mitogen-Activated Protein Kinases / metabolism*
  • Mutation
  • Neurospora crassa / enzymology*
  • Osmotic Pressure
  • Oxidation-Reduction
  • Oxidative Stress / genetics
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Pyrroles / pharmacology
  • Spores, Fungal

Substances

  • Dioxoles
  • Fungal Proteins
  • Protein Subunits
  • Pyrroles
  • Hydrogen Peroxide
  • Catalase
  • Mitogen-Activated Protein Kinases
  • os-2 protein, Neurospora crassa
  • fludioxonil