Disruption of SRM1, a mitogen-activated protein kinase gene, affects sensitivity to osmotic and ultraviolet stressors in the phytopathogenic fungus Bipolaris oryzae

• Published in: FEMS microbiology letters 2006-04, Vol.257 (2), p.253-261
• Main Authors: Moriwaki, Akihiro, Kubo, Emiko, Arase, Sakae, Kihara, Junichi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antioxidants; Ascomycota - genetics; Ascomycota - pathogenicity; Ascomycota - physiology; Ascomycota - radiation effects; Biological activity; Biological and medical sciences; Biosynthesis; Bipolaris oryzae; CAT2 gene; Catalase; Dicarboximide; Disruption; Fundamental and applied biological sciences. Psychology; Fungal Proteins - genetics; Fungal Proteins - metabolism; Fungal Proteins - physiology; Fungi; Fungicides; Gene expression; Gene Expression Regulation, Fungal; Genes; Glycerol; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; hog1; Hog1 protein; Homology; Hydrogen peroxide; Kinases; MAP kinase; Melanin; Microbiology; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Mitogen-Activated Protein Kinases - physiology; mitogen‐activated protein kinase; Molecular Sequence Data; Mutation; Mycology; Near ultraviolet radiation; Nitrogen Dioxide; Oryza - microbiology; Osmolarity; Osmotic Pressure; Oxidative Stress; Phosphorylation; Photomorphogenesis; Phytopathogenic fungi; Plant Diseases - microbiology; Plant Leaves - microbiology; Protein kinase; Proteins; Sequence Alignment; Transcription; ultraviolet (UV); Ultraviolet radiation; Ultraviolet Rays; Virulence; Yeast; Yeasts
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.2006.00178.x

abstract Mitogen-activated protein kinases (MAPKs) play key roles in biological processes including differentiation, growth, proliferation, survival, and stress responses. We isolated and characterized the SRM1 gene, which encodes an MAPK related to yeast High-osmolarity glycerol 1 (Hog1), from the rice leaf pathogen Bipolaris oryzae. The deduced amino sequence of the SRM1 gene showed significant homology with Hog1-type MAPK homologues from other phytopathogenic fungi and contained a TGY motif for phosphorylation. The B. oryzae mutants with disruption of the SRM1 gene (Δsrm1) showed growth inhibition under hyperosmotic, hydrogen peroxide, and UV exposure conditions. The Δsrm1 mutants showed moderate resistance to dicarboximide and phenylpyrrole fungicides. The Δsrm1 mutations caused a defect in the expression of the gene that encodes antioxidant enzyme catalase (CAT2) under UV and hyperosmotic conditions. Furthermore, the transcriptional patterns of the three melanin biosynthesis genes (PKS1, THR1, and SCD1) and of a gene of unknown function, uvi-1, which are specifically induced by near-ultraviolet (NUV) radiation, gradually decreased in comparison with the wild-type expression patterns. These results suggest that Srm1 contributes to responses to not only osmostress but also to hydrogen peroxide and UV stress, whereas Srm1 does not appear to regulate directly the expression of genes related to NUV-induced photomorphogenesis.