MUTANTS OF THE PHYTOPATHOGENIC FUNGUS MAGNAPORTHE-GRISEA DEFICIENT INALTERNATIVE, CYANIDE-RESISTANT, RESPIRATION

The phytopathogenic fungus Magnaporthe grisea has a cyanide-resistant respiratory pathway, The fungicide SSF-126 ((E)-2-methoxyimino-N-methy l-2-(2-phenoxyphenyl acetamide) blocks the cytochrome electron transpo rt of M. grisea and induces the alternative respiratory pathway, Twelv e mutants of M. grisea more susceptible to SSF-126 than wild type were identified after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Fi ve mutants retained a reduced alternative respiration activity, and se ven mutants lacked alternative pathway activity, A monoclonal antibody against the maize alternative oxidase cross-reacted against a 40-kDa mitochondrial protein of M. grisea, indicating that the 40-kDa protein is an alternative oxidase. Immunoblot analysis indicated that the sev en completely deficient mutants grouped into two classes: four mutants produced the 40-kDa proteins while the other three mutants failed to produce the functional protein. (C) 1997 Academic Press.