Variations in plant metallothioneins: the heavy metal hyperaccumulator <Emphasis Type="Italic">Thlaspi caerulescens</Emphasis> as a study case |
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Authors: | Email author" target="_blank">Nancy?H?RoosensEmail author Raphael?Leplae Catherine?Bernard Nathalie?Verbruggen |
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Institution: | (1) Laboratoire de Physiologie et Génétique Moléculaire des Plantes, Université Libre de Bruxelles, Campus Plaine (CP 242) Bd du triomphe, 1050 Brussels, Belgium;(2) Service de Conformation des Macromolécules Biologiques et bioinformatique, Université Libre de Bruxelles, Campus Plaine (CP263), 1050 Brussels, Belgium |
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Abstract: | Plant metallothioneins (MTs) are extremely diverse and are thought to be involved in metal homeostasis or detoxification.
Thlaspi caerulescens is a model Zn/Cd hyperaccumulator and thus constitutes an ideal system to study the variability of these MTs. Two T. caerulescens cDNAs (accession: 665511; accession: 665515), that are highly homologous to type 1 and type 2 Arabidopsis thaliana MTs, have been isolated using a functional screen for plant cDNAs that confer Cd tolerance to yeast. However, TcMT1 has a much shorter N-terminal domain than that of A. thaliana and so lacks Cys motifs conserved through all the plant MTs classified as type 1. A systematic search in plant databases
allowed the detection of MT-related sequences. Sixty-four percent fulfil the criteria for MT classification described in Cobbett
and Goldsbrough (2002) and further extend our knowledge about other conserved residues that might play an important role in plant MT structure.
In addition, 34% of the total MT-related sequences cannot be classified strictly as they display modifications in the conserved
residues according to the current plant MTs’ classification. The significance of this variability in plant MT sequences is
discussed. Functional complementation in yeast was used to assess whether these variations may alter the MTs’ function in
T. caerulescens. Regulation of the expression of MTs in T. caerulescens was also investigated. TcMT1 and TcMT2 display higher expression in T. caerulescens than in A. thaliana. Moreover, their differential expression patterns in organs and in response to metal exposure, suggest that the two types
of MTs may have diverse roles and functions in T. caerulescens. |
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Keywords: | Cadmium Heavy metal stress Metallothionein Metal homeostasis Metal hyperaccumulation Thlaspi caerulescens |
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