Effects of disrupting the polyketide synthase gene WdPKS1 in Wangiella [Exophiala] dermatitidis on melanin production and resistance to killing by antifungal compounds, enzymatic degradation, and extremes in temperature
MetadataShow full item record
Background: Wangiella dermatitidis is a human pathogenic fungus that is an etiologic agent of phaeohyphomycosis. W. dermatitidis produces a black pigment that has been identified as a dihydroxynaphthalene melanin and the production of this pigment is associated with its virulence. Cell wall pigmentation in W. dermatitidis depends on the WdPKS1 gene, which encodes a polyketide synthase required for generating the key precursor for dihydroxynaphthalene melanin biosynthesis. -- Results: We analyzed the effects of disrupting WdPKS1 on dihydroxynaphthalene melanin production and resistance to antifungal compounds. Transmission electron microscopy revealed that wdpks1Δ-1 yeast had thinner cell walls that lacked an electron-opaque layer compared to wild-type cells. However, digestion of the wdpks1Δ-1 yeast revealed small black particles that were consistent with a melanin-like compound, because they were acid-resistant, reacted with melanin-binding antibody, and demonstrated a free radical signature by electron spin resonance analysis. Despite lacking the WdPKS1 gene, the mutant yeast were capable of catalyzing the formation of melanin from L-3,4-dihyroxyphenylalanine. The wdpks1Δ-1 cells were significantly more susceptible to killing by voriconazole, amphotericin B, NP-1 [a microbicidal peptide], heat and cold, and lysing enzymes than the heavily melanized parental or complemented strains. -- Conclusion: In summary, W. dermatitidis makes WdPKS-dependent and -independent melanins, and the WdPKS1-dependent deposition of melanin in the cell wall confers protection against antifungal agents and environmental stresses. The biological role of the WdPKS-independent melanin remains unclear.
William F. Paolo Jr., Arturo Casadevall, and Joshua D. Nosanchuk are with the Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA -- Ekaterina Dadachova, Piyali Mandal, Arturo Casadevall, and Joshua D. Nosanchuk are with the Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA -- Ekaterina Dadachova is with the Department of Nuclear Medicine, Albert Einstein College of Medicine, Bronx, NY, USA -- Piyali Mandal is with the Department of Microbiology, All India Institute of Medical Sciences and Division of Infectious Diseases, New Delhi, India -- Paul J. Szaniszlo is with the Section of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, TX, USA -- 6 Department of Medicine, New York University Medical Center, NY, USA