Laccase is a copper containing polyphenol oxidase widely distributed among plants and fungi. Fungal laccases are involved in such divers processes as lignin degradation, morphogenesis and pathogenic interactions. Laccase I (yA) of Aspergillus nidulans is involved in pigment synthesis of asexual spores. In contrast, laccase lI was described as differentially expressed during sexual spore development. During an approach to identify the laccase II gene of A. nidulans a partial laccase sequence appeared in the EST sequencing project (University of Oklahoma). We subsequently have cloned and sequenced the whole gene. The deduced amino acid sequence was not laccase II and thus the novel gene was named lac3. lac3 codes for a protein of 595 as with highest homology to laccase I of A. nidulans (36% identical aa). Laccase III was immuno-cytochemically localized in the hyphal cell wall. Expression of the enzyme starts at the onset of conidiospore germination and highest concentrations of the protein were detected at the hyphal tip suggesting a crucial function for cell extension. Western blot analysis showed that laccase III is present throughout the vegetative and asexual stage of the fungus, whereas it could not be detected during late sexual development. Knock out and overexpression experiments are in progress to prove the role of laccase III in hyphal tip extension.
Fungal Genet. Newsl. 46 (Supl):
Full conference title:
Fungal Genetics Conference 20th
- Fungal Genetics Conference 20th (1999)