Cloning and disruption of a phenylalanine ammonia-lyase gene from Ustilago maydis

The enzyme L-phenylalanine ammonia-lyase (PAL) catalyzes the non-oxidative deamination of L-phenylalanine to form trans-cinnamic acid and ammonia. This enzyme is universally present in higher plants and it catalyzes the starting reaction for a central pathway that generates hundreds of different phenylpropanoid metabolites. Genes encoding PAL have been identified in fungi, but the role of the enzyme has not been determined. We cloned and characterized a gene that encodes PAL from the phytopathogenic fungus Ustilago maydis and we constructed fungal strains carrying a null mutation in the gene. These mutants behaved like wild-type strains in terms of growth, mating, and pathogenicity. These results indicate that PAL does not play a major role in the life cycle of U. maydis under laboratory conditions.