title: Mechanism of arsenate resistance in the ericoid mycorrhizal fungus Hymenoscyphus ericae.
abstract: Arsenate resistance is exhibited by the ericoid mycorrhizal fungus Hymenoscyphus ericae collected from As-contaminated mine soils. To investigate the mechanism of arsenate resistance, uptake kinetics for arsenate (H(2)AsO(4)(-)), arsenite (H(3)AsO(3)), and phosphate (H(2)PO(4)(-)) were determined in both arsenate-resistant and -non-resistant H. ericae. The uptake kinetics of H(2)AsO(4)(-), H(3)AsO(3), and H(2)PO(4)(-) in both resistant and non-resistant isolates were similar. The presence of 5.0 microM H(2)PO(4)(-) repressed uptake of H(2)AsO(4)(-) and exposure to 0.75 mM H(2)AsO(4)(-) repressed H(2)PO(4)(-) uptake in both H. ericae. Mine site H. ericae demonstrated an enhanced As efflux mechanism in comparison with non-resistant H. ericae and lost approximately 90% of preloaded cellular As (1-h uptake of 0.22 micromol g(-1) dry weight h(-1) H(2)AsO(4)(-)) over a 5-h period in comparison with non-resistant H. ericae, which lost 40% of their total absorbed H(2)AsO(4)(-). As lost from the fungal tissue was in the form of H(3)AsO(3). The results of the present study demonstrate an enhanced H(3)AsO(3) efflux system operating in mine site H. ericae as a mechanism for H(2)AsO(4)(-) resistance. The ecological significance of this mechanism of arsenate resistance is discussed.
authors.affiliation: Mycorrhiza Research Group, School of Science, University of Western Sydney, P.O. Box 10, Kingswood NSW 2747, Australia.
authors.forename: J M
authors.initials: JM
authors.lastname: Sharples
authors.forename: A A
authors.initials: AA
authors.lastname: Meharg
authors.forename: S M
authors.initials: SM
authors.lastname: Chambers
authors.forename: J W
authors.initials: JW
authors.lastname: Cairney
mesh_terms: D001149:Arsenates / Q000378:metabolism*; D018053:Arsenites / Q000378:metabolism*; D001203:Ascomycota / Q000378:metabolism*; D001673:Biodegradation, Environmental; D001692:Biological Transport; D018533:Biomass; D019684:Magnoliopsida / Q000254:growth & development / Q000382:microbiology; D008906:Mining; D010710:Phosphates / Q000378:metabolism; D012989:Soil Pollutants / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D001149:Arsenates; D018053:Arsenites; D010710:Phosphates; D012989:Soil Pollutants