Involvement of OS-2 MAP kinase in regulation of the large-subunit catalases CAT-1 and CAT-3 in Neurospora crassa.
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.
Yamashita
Kazuhiro
K
Faculty of Life Sciences, Toyo University, Itakura, Gunma, Japan.
Shiozawa
Azusa
A
Banno
Shinpei
S
Fukumori
Fumiyasu
F
Ichiishi
Akihiko
A
Kimura
Makoto
M
Fujimura
Makoto
M
D002374:Catalase / Q000235:genetics* / Q000378:metabolism; D004149:Dioxoles / Q000494:pharmacology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D006861:Hydrogen Peroxide / Q000494:pharmacology; D025301:Hyphae / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009154:Mutation; D009492:Neurospora crassa / Q000201:enzymology*; D009997:Osmotic Pressure; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011758:Pyrroles / Q000494:pharmacology; D013172:Spores, Fungal
D004149:Dioxoles; D005656:Fungal Proteins; D021122:Protein Subunits; D011758:Pyrroles; D006861:Hydrogen Peroxide; D002374:Catalase; D020928:Mitogen-Activated Protein Kinases; C450461:os-2 protein, Neurospora crassa; C108339:fludioxonil