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Metal induction of a P isolithus albus metallothionein and its potential involvement in heavy metal tolerance during mycorrhizal symbiosis
Author(s) -
Reddy M. Sudhakara,
Kour Manpreet,
Aggarwal Sipla,
Ahuja Shanky,
Marmeisse Roland,
FraissinetTachet Laurence
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13149
Subject(s) - biology , metallothionein , symbiosis , complementation , mutant , botany , biochemistry , cysteine , pisolithus , mycorrhiza , proline , fungus , metal , amino acid , bacteria , gene , enzyme , genetics , chemistry , organic chemistry
Summary 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 P isolithus 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 C u and C d concentrations and were higher with C u than with C d. Heterologous complementation assays in metal‐sensitive yeast mutants indicated that PaMT1 encodes a polypeptide capable of conferring higher tolerance to both C u and C d. E ucalyptus tereticornis plantlets colonized with P . albus grown in the presence of C u and C d showed better growth compared with those with non‐mycorrhizal plants. Higher PaMT1 expression levels were recorded in mycorrhizal plants grown in the presence of C u and C d 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.