In this study, novel polyketide biosynthesis gene cluster of Aspergillus
fumigatus was characterized and functionally analyzed. Analysis of the newly
sequenced A. fumigatus genome for laccases, which are involved in melanin
biosynthesis and detoxification in fungi, resulted in several putative laccase and
multicopper oxidase gene sequences, one of which, Afu4g14490 (tpnJ), was selected
for further characterization. The predicted amino acid sequence TpnJp showed 63%
identity with the dihydrogeodin oxidase of Aspergillus terreus, which is involved in
the biosynthesis of the antifungal geodin. When the genome region of tpnJ was
investigated, the presence of a polyketide biosynthesis gene cluster containing 13
genes, hypothesized to be responsible for the production of trypacidin and
monomethylsulochrin, was realized. By a comparative genomics approach, a putative
geodin biosynthesis gene cluster containing 13 genes, including dihydrogeodin
oxidase, in A. terreus and a putative trypacidin biosynthesis gene cluster containing
13 genes in N. fischeri were established. Targeted deletions of the polyketide
synthase (tpnC) and multicopper oxidase (tpnJ) genes confirmed the hypothesis that TpnCp, a three-domain minimal polyketide synthase, is involved in trypacidin and
monomethylsulochrin biosynthesis in A. fumigatus. TpnCp is the first fungal minimal
polyketide synthase whose functional role was experimentally identified. Moreover,
the fact that LC-MS analysis of DtpnJ strain showed the absence of trypacidin and
the presence of a higher amount of monomethylsulochrin in DtpnJ strain, confirmed
the hypothesis that TpnJp is involved in the oxidation of monomethylsulochrin into
trypacidin. This novel multicopper oxidase having high substrate specificity is given
the name monomethylsulochrin oxidase.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12609029/index.pdf |
| Date | 01 October 2007 |
| Creators | Metin, Banu |
| Contributors | Ogel, Zumrut Begum |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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