title: Differential expression of metallothioneins in response to heavy metals and their involvement in metal tolerance in the symbiotic basidiomycete Laccaria bicolor.
abstract: Cysteine-rich peptides such as metallothioneins (MTs) are involved in metal homeostasis and detoxification in many eukaryotes. We report the characterization and expression of two MT genes, LbMT1 and LbMT2 from the ectomycorrhizal fungus Laccaria bicolor under metal stress conditions. LbMT1 and LbMT2 differ with respect to the length of the encoded peptides (58 versus 37 aa, respectively) and also by their expression patterns in response to metals. The expression levels of both LbMT1 and LbMT2 increased as a function of increased external Cu concentration, the expression levels for LbMT2 were always significantly higher compared with those of LbMT1. Only LbMT1, but not LbMT2, responded to Cd supply in the range of 25-100 µM while Zn did not affect the transcription of either LbMT1 or LbMT2. Both genes also responded to oxidative stress, but to a lesser extent compared to their responses to either Cu or Cd stress. Heterologous complementation assays in metal-sensitive yeast mutants indicated that both LbMT1 and LbMT2 encode peptides capable of conferring higher tolerance to both Cu and Cd. The present study identified LbMTs as potential determinants of the response of this mycorrhizal fungus to Cu and Cd stress.
authors.affiliation: Thapar University, Department of Biotechnology, Bhadson Road, Patiala 147 004, India.
authors.forename: M Sudhakara
authors.initials: MS
authors.lastname: Reddy
authors.affiliation: Department of Biological Sciences, University of Alabama in Huntsville, Huntsville, AL 35899, USA.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Prasanna
authors.affiliation: Microbial Ecology, CNRS UMR 5557, USC INRA 1364, Université Lyon1, Université de Lyon F-69622 Villeurbanne, France.
authors.forename: R
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: L
authors.initials: L
authors.lastname: Fraissinet-Tachet
mesh_terms: D004361:Drug Tolerance; D020869:Gene Expression Profiling; D055399:Laccaria / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D019216:Metals, Heavy / Q000378:metabolism* / Q000633:toxicity; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D017422:Sequence Analysis, DNA
chemical_list: D019216:Metals, Heavy; D008668:Metallothionein