title: Zinc export results in adaptive zinc tolerance in the ectomycorrhizal basidiomycete Suillus bovinus.
abstract: On Zn-polluted soils, populations of the ectomycorrhizal basidiomycete Suillus bovinus exhibit an elevated Zn tolerance when compared to populations on non-polluted sites. To elucidate the mechanism of Zn tolerance, the time-course of Zn uptake was studied in isolates with contrasting Zn tolerance. Unidirectional fluxes and subcellular compartmentation of Zn were investigated through radiotracer flux analyses. Fluorescence imaging was used to support the subcellular Zn compartmentation. After 2 h of exposure to 200 μM Zn, significantly more Zn was accumulated in Zn-sensitive isolates compared to tolerant isolates, despite similar short-term uptake kinetics and similar extracellular Zn sequestration in cell walls. In Zn-sensitive isolates twice as much Zn accumulated in the cytoplasm and 12 times more Zn in the vacuole. (65)Zn efflux analyses revealed a considerably faster Zn export in the Zn-tolerant isolate. The adaptive Zn tolerance in S. bovinus is therefore achieved by a preferential removal of Zn out of the cytoplasm, back into the apoplast, instead of the usual transfer of Zn into the vacuole. Zn exclusion in the fungal symbiont eventually contributes to a lower Zn influx in host plants.
authors.affiliation: Hasselt University, Centre for Environmental Sciences, Environmental Biology Group, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium.
authors.forename: Joske
authors.initials: J
authors.lastname: Ruytinx
authors.forename: Hoai
authors.initials: H
authors.lastname: Nguyen
authors.forename: May
authors.initials: M
authors.lastname: Van Hees
authors.forename: Michiel
authors.initials: M
authors.lastname: Op De Beeck
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.forename: Robert
authors.initials: R
authors.lastname: Carleer
authors.forename: Jan V
authors.initials: JV
authors.lastname: Colpaert
authors.forename: Kristin
authors.initials: K
authors.lastname: Adriaensen
mesh_terms: D000222:Adaptation, Physiological; D001487:Basidiomycota / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002473:Cell Wall / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D007700:Kinetics; D025282:Mycelium / Q000378:metabolism; D038821:Mycorrhizae / Q000378:metabolism*; D061209:Proton Ionophores / Q000494:pharmacology; D012989:Soil Pollutants / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D061209:Proton Ionophores; D012989:Soil Pollutants; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D015032:Zinc