Merging methods in molecular and ecological genetics to study the adaptation of plants to anthropogenic metal-polluted sites: implications for phytoremediation

Authors

  • MAXIME PAUWELS,

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    • Present address: Institut de Recherche sur la Biologie de l’Insecte, UMR CNRS 6035, Faculté des Sciences, Bâtiment I, 31 Avenue Monge, 37200 Tours, France

  • GLENDA WILLEMS,

    1. Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, Université des Sciences et Technologies de Lille, Bâtiment SN2, F-59655 Villeneuve d’Ascq Cedex, France
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  • NANCY ROOSENS,

    1. Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, Université des Sciences et Technologies de Lille, Bâtiment SN2, F-59655 Villeneuve d’Ascq Cedex, France
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  • HÉLÈNE FRÉROT,

    1. Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, Université des Sciences et Technologies de Lille, Bâtiment SN2, F-59655 Villeneuve d’Ascq Cedex, France
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  • PIERRE SAUMITOU-LAPRADE

    1. Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, Université des Sciences et Technologies de Lille, Bâtiment SN2, F-59655 Villeneuve d’Ascq Cedex, France
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  • Box 1  Definition of heavy-metal tolerance: a complex plant–environment interaction

    Heavy-metal tolerance is the capacity of a plant to survive and reproduce in a highly metal-polluted soil, toxic for most other plants (Antonovics et al. 1971; Macnair 1987).

    Physiological aspects

    How do metal-tolerant plants respond to high metal concentrations?inline image

    Accumulation and exclusion are the two main ways in which plants respond to increasing soil-metal levels, reflected by the metal concentrations in aerial plant parts. Excluders loose the control of metal translocation to aerial parts beyond a threshold of soil metal level. Hyperaccumulators are particular accumulators that show elevated metal concentrations in aerial parts mainly as a result of an enhanced root-to-shoot translocation (Lasat et al. 1996; Clemens 2001).

    Research focus: What are the physiological pathways responsible for heavy-metal tolerance? Are they different between excluders, indicators and (hyper) accumulators?

    Ecological Aspects

    Is metal tolerance specific of plants from polluted soils?inline image

    ‘Non-tolerant,’ or ‘metal-tolerant’ refers to the plant genotype while ‘non-metalliferous’ or ‘metalliferous’ refers to the soil type. Non-metallicolous populations (NM) develop on non-metalliferous soils and metallicolous populations (M) develop on metalliferous soils. Non metallophytes (A category) never occur on metalliferous soils (no M populations). Pseudometallophyte (B and C categories) have metallicolous and non-metallicolous populations in various relative proportions (NM > M or NM < M). Eumetallophytes (D category) always occur on metalliferous soils (metalloendemics, no NM population).

    Research focus: What is the origin of the genetic variability of heavy-metal tolerance? How do metal tolerant genotypes maintain in non-metalliferous soils?

Pierre Saumitou-Laprade, Fax: +33 320436979; E-mail: pierre.saumitou@univ-lille1.fr

Abstract

Metallophyte species that occur naturally on metal-enriched soils represent major biological resources for the improvement of phytoremediation, a benign and cost-effective technology that uses plants to clean up anthropogenic metal-polluted soils. Within the last decade, molecular genetic studies carried out on several model organisms (including Arabidopsis halleri) have considerably enhanced our understanding of metal tolerance and hyperaccumulation in plants, but the identification of the genes of interest for phytoremediation purposes remains a challenge. To meet this challenge, we propose to combine ‘-omics’ with molecular ecology methods. Using A. halleri, we confronted molecular genetic results with: (i) within-species polymorphism and large-scale population differentiation for zinc tolerance; (ii) the demographical context (e.g. migration pattern) of the species for zinc tolerance evolution; (iii) the Quantitative Trait Loci (QTL) analysis of the genetic architecture for zinc tolerance; and (iv) the fine-scale dissection of identified QTL regions, to discuss more precisely the nature of the genes potentially involved in the adaptation to zinc-polluted soils.

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