Cloning, Characterization, and Transcription of Three Laccase Genes from Gaeumannomyces graminis var. tritici , the Take-All Fungus

Abstract

ABSTRACT Gaeumannomyces graminis var. tritici , a filamentous ascomycete, is an important root pathogen of cereals that causes take-all disease and results in severe crop losses worldwide. Previously we identified a polyphenol oxidase (laccase) secreted by the fungus when induced with copper. Here we report cloning and partial characterization of three laccase genes ( LAC1 , LAC2 , and LAC3 ) from G. graminis var. tritici. Predicted polypeptides encoded by these genes had 38 to 42% amino acid sequence identity and had conserved copper-binding sites characteristic of laccases. The sequence of the LAC2 predicted polypeptide matched the N-terminal sequence of the secreted laccase that we purified in earlier studies. We also characterized expression patterns of these genes by reverse transcription-PCR. LAC1 was transcribed constitutively, and transcription of LAC2 was Cu inducible. All three genes were transcribed in planta; however, transcription of LAC3 was observed only in planta or in the presence of host (wheat) plant homogenate.