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Watanabe T, Shitan N, Suzuki S, Umezawa T, Shimada M, Yazaki K, Hattori T. Oxalate efflux transporter from the brown rot fungus Fomitopsis palustris. Appl Environ Microbiol 2010; 76:7683-90. [PMID: 20889782 PMCID: PMC2988596 DOI: 10.1128/aem.00829-10] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2010] [Accepted: 09/21/2010] [Indexed: 01/18/2023] Open
Abstract
An oxalate-fermenting brown rot fungus, Fomitopsis palustris, secretes large amounts of oxalic acid during wood decay. Secretion of oxalic acid is indispensable for the degradation of wood cell walls, but almost nothing is known about the transport mechanism by which oxalic acid is secreted from F. palustris hyphal cells. We characterized the mechanism for oxalate transport using membrane vesicles of F. palustris. Oxalate transport in F. palustris was ATP dependent and was strongly inhibited by several inhibitors, such as valinomycin and NH(4)(+), suggesting the presence of a secondary oxalate transporter in this fungus. We then isolated a cDNA, FpOAR (Fomitopsis palustris oxalic acid resistance), from F. palustris by functional screening of yeast transformants with cDNAs grown on oxalic acid-containing plates. FpOAR is predicted to be a membrane protein that possesses six transmembrane domains but shows no similarity with known oxalate transporters. The yeast transformant possessing FpOAR (FpOAR-transformant) acquired resistance to oxalic acid and contained less oxalate than the control transformant. Biochemical analyses using membrane vesicles of the FpOAR-transformant showed that the oxalate transport property of FpOAR was consistent with that observed in membrane vesicles of F. palustris. The quantity of FpOAR transcripts was correlated with increasing oxalic acid accumulation in the culture medium and was induced when exogenous oxalate was added to the medium. These results strongly suggest that FpOAR plays an important role in wood decay by acting as a secondary transporter responsible for secretion of oxalate by F. palustris.
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Affiliation(s)
- Tomoki Watanabe
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Nobukazu Shitan
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shiro Suzuki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Toshiaki Umezawa
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Mikio Shimada
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kazufumi Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Takefumi Hattori
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan, Institute of Sustainable Science, Kyoto University, Uji, Kyoto 611-0011, Japan
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