Linoleate diol synthase of the rice blast fungus Magnaporthe grisea.

Abstract

Mycelia of two strains of Magnaporthe grisea, Guy 11 and TH3, were incubated with linoleic acid, and the metabolites were isolated and identified by GC-MS and LC-MS. The two main metabolites were identified as 8-hydroxylinoleic and 7,8-dihydroxylinoleic acids, and the former was further oxidized by n-2 and by n-3 hydroxylation to 8,16- and 8,17-dihydroxylinoleic acids. Lipoxygenase metabolites of linoleic acid could not be detected. The sequence of the genome of M. grisea has been released from the Whitehead Institute; it contains a gene with close homology to the linoleate diol synthase gene of the take-all fungus Gaeumannomyces graminis. Both genes appear to have the same organization, with four exons and three short introns, and the intron-exon borders were determined by reverse-transcription PCR and sequencing. The linoleate diol synthase precursor of G. graminis consists of 978 amino acids, whereas the putative diol synthase precursor of M. grisea contains 987 amino acids. The diol synthases of G. graminis and M. grisea can be aligned with 65% identical and 78% positive amino acid residues, and catalytically important amino acid residues were conserved.