title: Identification and function of a polyketide synthase gene responsible for 1,8-dihydroxynaphthalene-melanin pigment biosynthesis in Ascochyta rabiei.
abstract: Ascochyta rabiei produces and accumulates one of the well-known fungal polyketides, 1,8-dihydroxynaphthalene-melanin pigment (DHN-melanin), in asexual and sexual fruiting bodies. Degenerate PCR primers were used to isolate an ArPKS1 of A. rabiei encoding a polypeptide with high similarity to polyketide synthase (PKS) involved in biosynthesis of DHN-melanin in other ascomycetous fungi. Site-directed mutagenesis of ArPKS1 in A. rabiei generated melanin-deficient pycnidial mutants but caused no significant reduction of pathogenicity to chickpea. Pycnidiospores in ArPKS1-mutant pycnidia showed higher sensitivity to UV light exposure compared to pycnidiospores in melanized pycnidia of the wild-type progenitor isolate. Integration of an orthologous PKS1 gene from Bipolaris oryzae into the genome of the mutants complemented the dysfunctional ArPKS1 gene. This study demonstrated that A. rabiei uses a DHN-melanin pathway for pigmentation of pycnidia and this molecule may protect pycnidiospores from UV irradiation.
authors.affiliation: Department of Plant Pathology, Washington State University, Pullman, WA 99164-6430, USA. akamatho@affrc.go.jp
authors.forename: Hajime O
authors.initials: HO
authors.lastname: Akamatsu
authors.forename: Martin I
authors.initials: MI
authors.lastname: Chilvers
authors.forename: Jane E
authors.initials: JE
authors.lastname: Stewart
authors.forename: Tobin L
authors.initials: TL
authors.lastname: Peever
mesh_terms: D001203:Ascomycota / Q000201:enzymology / Q000235:genetics*; D017931:DNA Primers; D008543:Melanins / Q000096:biosynthesis* / Q000172:deficiency; D016297:Mutagenesis, Site-Directed; D009284:Naphthols; D010860:Pigments, Biological; D048630:Polyketide Synthases / Q000235:genetics* / Q000302:isolation & purification; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: C423455:1,8-dihydroxynaphthalene melanin; D017931:DNA Primers; D008543:Melanins; D009284:Naphthols; D010860:Pigments, Biological; D048630:Polyketide Synthases
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