Terbinafine resistance mediated by salicylate 1-monooxygenase in Aspergillus nidulans.
Resistance to antifungal agents is a recurring and growing problem among patients with systemic fungal infections. UV-induced Aspergillus nidulans mutants resistant to terbinafine have been identified, and we report here the characterization of one such gene. A sib-selected, 6.6-kb genomic DNA fragment encodes a salicylate 1-monooxygenase (salA), and a fatty acid synthase subunit (fasC) confers terbinafine resistance upon transformation of a sensitive strain. Subfragments carrying salA but not fasC confer terbinafine resistance. salA is present as a single-copy gene on chromosome VI and encodes a protein of 473 amino acids that is homologous to salicylate 1-monooxygenase, a well-characterized naphthalene-degrading enzyme in bacteria. salA transcript accumulation analysis showed terbinafine-dependent induction in the wild type and the UV-induced mutant Terb7, as well as overexpression in a strain containing the salA subgenomic DNA fragment, probably due to the multicopy effect caused by the transformation event. Additional naphthalene degradation enzyme-coding genes are present in fungal genomes, suggesting that resistance could follow degradation of the naphthalene ring contained in terbinafine.
Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, 14049-900 Ribeirão Preto, Sao Paulo, Brazil.
Marcia A S
MA
Graminha
Eleusa M F
EM
Rocha
Rolf A
RA
Prade
Nilce M
NM
Martinez-Rossi
D000935:Antifungal Agents / Q000378:metabolism / Q000494:pharmacology*; D001233:Aspergillus nidulans / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D015152:Blotting, Northern; D015139:Blotting, Southern; D002874:Chromosome Mapping; D003470:Culture Media; D053938:DNA Fragmentation / Q000235:genetics; D017931:DNA Primers; D004271:DNA, Fungal / Q000235:genetics; D025141:Drug Resistance, Fungal; D064429:Fatty Acid Synthases / Q000378:metabolism; D015723:Gene Library; D005800:Genes, Fungal / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000502:physiology*; D009281:Naphthalenes / Q000378:metabolism / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077291:Terbinafine; D014158:Transcription, Genetic; D014170:Transformation, Genetic
D000935:Antifungal Agents; D003470:Culture Media; D017931:DNA Primers; D004271:DNA, Fungal; D009281:Naphthalenes; D006899:Mixed Function Oxygenases; C022619:salicylate 1-monooxygenase; D064429:Fatty Acid Synthases; D000077291:Terbinafine