title: Metal induction of a Pisolithus albus metallothionein and its potential involvement in heavy metal tolerance during mycorrhizal symbiosis.
abstract: Metallothioneins (MTs) are small, cysteine-rich peptides involved in intracellular sequestration of heavy metals in eukaryotes. We examined the role in metal homeostasis and detoxification of an MT from the ectomycorrhizal fungus Pisolithus albus (PaMT1). PaMT1 encodes a 35 amino acid-long polypeptide, with 7 cysteine residues; most of them part of a C-x-C motif found in other known basidiomycete MTs. The expression levels of PaMT1 increased as a function of increased external Cu and Cd concentrations and were higher with Cu than with Cd. Heterologous complementation assays in metal-sensitive yeast mutants indicated that PaMT1 encodes a polypeptide capable of conferring higher tolerance to both Cu and Cd. Eucalyptus tereticornis plantlets colonized with P. albus grown in the presence of Cu and Cd showed better growth compared with those with non-mycorrhizal plants. Higher PaMT1 expression levels were recorded in mycorrhizal plants grown in the presence of Cu and Cd compared with those in control mycorrhizal plants not exposed to heavy metals. These data provide the first evidence to our knowledge that fungal MTs could protect ectomycorrhizal fungi from heavy metal stress and in turn help the plants to establish in metal-contaminated sites.
authors.affiliation: Department of Biotechnology, Thapar University, Bhadson Road, Patiala, 147 004, India.
authors.forename: M Sudhakara
authors.initials: MS
authors.lastname: Reddy
authors.affiliation: Department of Biotechnology, Thapar University, Bhadson Road, Patiala, 147 004, India.
authors.forename: Manpreet
authors.initials: M
authors.lastname: Kour
authors.affiliation: Department of Biotechnology, Thapar University, Bhadson Road, Patiala, 147 004, India.
authors.forename: Sipla
authors.initials: S
authors.lastname: Aggarwal
authors.affiliation: Department of Biotechnology, Thapar University, Bhadson Road, Patiala, 147 004, India.
authors.forename: Shanky
authors.initials: S
authors.lastname: Ahuja
authors.affiliation: Microbial Ecology, CNRS UMR 5557, USC INRA 1364, Université Lyon1, Université de Lyon, F-69622, Villeurbanne, France.
authors.forename: Roland
authors.initials: R
authors.lastname: Marmeisse
authors.affiliation: Microbial Ecology, CNRS UMR 5557, USC INRA 1364, Université Lyon1, Université de Lyon, F-69622, Villeurbanne, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Fraissinet-Tachet
mesh_terms: D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity*; D003300:Copper / Q000633:toxicity*; D005052:Eucalyptus / Q000187:drug effects / Q000382:microbiology*; D008668:Metallothionein / Q000378:metabolism*; D038821:Mycorrhizae / Q000378:metabolism*; D063245:Plant Development / Q000187:drug effects / Q000502:physiology; D016415:Sequence Alignment; D013559:Symbiosis
chemical_list: D002104:Cadmium; D003300:Copper; D008668:Metallothionein