Genes for multicopper proteins and laccase activity: common features in plant-associatedFusariumisolates

Abstract

Eight Fusarium isolates from diverse plant habitats produced laccase activities when cultured on low-carbon medium. Three sequences with high homology to laccase genes were detected in the genome of Fusarium proliferatum, NRRL 31071, an opportunistic pathogen of wheat (Triticum spp.). The sequences aligned with laccase genes from Ascomycetes, whereas genes from other fungal taxonomic groups and from plants grouped separately. Sequences for related multicopper oxidases with ascorbate oxidase activity were also separated discretely. A fourth sequence from NRRL 31071 had highest homology to genes for multicopper proteins associated with ferrooxidase activities in yeasts. Each of the four sequences had high homology to sequences within the genome of a ligninolytic F. proliferatum from forest soil. RFLP analysis of the genomes of three other F. proliferatum isolates and a phylogenetically closely related isolate, Fusarium fujikuroi, showed that fragments hybridizing with the four multicopper oxidase genes were similar in size to those from the NRRL 31071 genome. Weaker hybridization was observed with the phylogenetically more distant Fusarium anthophilum. No hybridization was observed with an isolate of Fusarium culmorum, a wheat pathogen, from a different section of the genus Fusarium, although this isolate produced laccases.Key words: ferrooxidase, Fusarium proliferatum, laccase, multicopper oxidase.