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Lead tolerance and accumulation in Hirschfeldia incana, a Mediterranean Brassicaceae from metalliferous mine spoils.

Auguy F, Fahr M, Moulin P, Brugel A, Laplaze L, Mzibri ME, Filali-Maltouf A, Doumas P, Smouni A - PLoS ONE (2013)

Bottom Line: The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants.Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation.H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.

View Article: PubMed Central - PubMed

Affiliation: Institut de Recherche pour le Développement, Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes, Montpellier, France.

ABSTRACT
Lead is a heavy metal of particular concern with respect to environmental quality and health. The lack of plant species that accumulate and tolerate Pb is a limiting factor to understand the molecular mechanisms involved in Pb tolerance. In this study we identified Hirschfeldia incana, a Brassicaceae collected from metalliferous mine spoils in Morocco, as a Pb accumulator plant. H. incana exhibited high Pb accumulation in mine soils and in hydroponic cultures. Major Pb accumulation occurred in the roots and a part of Pb translocated from the roots to the shoots, even to the siliques. These findings demonstrated that H. incana is a Pb accumulator species. The expression of several candidate genes after Pb-exposure was measured by quantitative PCR and two of them, HiHMA4 and HiMT2a, coding respectively for a P1B-type ATPase and a metallothionein, were particularly induced by Pb-exposure in both roots and leaves. The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants. Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation. H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.

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Amount of metallic trace elements (As, Cd, Cu, Ni, Pb and Zn) in shoots of H. incana.Plants were collected from different zones in a heavy metal-polluted area. Data are the average (± SE) of six independent measurements. Amount (average ± SE) of metallic trace elements in the soil (mg/Kg): As = 298±80; Cd = 10±4; Cu = 459±88; Ni = 13±6, Pb = 7157±746; Zn = 14164±1460.
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pone-0061932-g001: Amount of metallic trace elements (As, Cd, Cu, Ni, Pb and Zn) in shoots of H. incana.Plants were collected from different zones in a heavy metal-polluted area. Data are the average (± SE) of six independent measurements. Amount (average ± SE) of metallic trace elements in the soil (mg/Kg): As = 298±80; Cd = 10±4; Cu = 459±88; Ni = 13±6, Pb = 7157±746; Zn = 14164±1460.

Mentions: An exploration of the flora from mining sites in Oued El Himer region, located in the south of Oujda city (Eastern Morocco), was conducted in order to identify new species able to accumulate heavy metals in their shoots for a future phytoremediation project. The sites we studied have been heavily affected by lead mining and smelting activities, and soils are subject of a polymetallic contamination [24]. In these areas, lead concentrations in soils varied from 26 to 9479 mg.kg−1[24]. Plants were collected and leaf samples were analyzed by ICP-AES in order to quantify heavy metal contents. The Brassicaceae H. incana was particularly interesting because of its accumulation profile of toxic heavy metals in leaf tissue (Figure 1). In natural conditions, this species presented a high level of Pb in leaves ranging from 0.53 to 1.43 mg.g−1 DW with an average of 0.79 mg.g−1 DW (Figure 1). The other metals analyzed were present at lower concentration such as Cd or Zn with an average of 0.04 and 0.11 mg.g−1 DW respectively even if the concentrations of these metals were high in the different sampled soils [24]. These results show that H. incana seems to be highly specific for Pb accumulation in accordance to the contents of the different heavy metals analyzed. In order to confirm the accumulator trait observed in natural conditions and to avoid air-borne contamination such as dust deposits, H. incana plants were grown under controlled growth chamber conditions on four different soils collected in metalliferous mine spoils. These soils contained various amounts of total Pb (soil 1∶6973 mg.kg−1 DW; soil 2∶18626 mg.kg−1 DW; soil 3∶7531 mg.kg−1 DW; soil 4∶1577 mg.kg−1 DW, table 1). After 2 months of culture, Pb content was quantified in the shoots (Figure 2). The concentration of Pb in leaves was variable from a minimum of 0.43 mg.g−1 DW for plants grown on soil 1 to a maximum of 3.58 mg.g−1 DW for those grown on soil 3. These results confirmed the lead hyperaccumulator trait for H. incana. On the other hand, no correlation was observed between total Pb content in the different soils and Pb level in the plant tissues suggesting variations in the amount of bioavailable lead. CaCl2 and EDTA extractible fractions corresponding respectively to the mobile and the mobilisable fractions were quantified (Table 1). No correlation could be demonstrated between the Pb levels of the extractible fractions and those of the H. incana assimilated fraction.


Lead tolerance and accumulation in Hirschfeldia incana, a Mediterranean Brassicaceae from metalliferous mine spoils.

Auguy F, Fahr M, Moulin P, Brugel A, Laplaze L, Mzibri ME, Filali-Maltouf A, Doumas P, Smouni A - PLoS ONE (2013)

Amount of metallic trace elements (As, Cd, Cu, Ni, Pb and Zn) in shoots of H. incana.Plants were collected from different zones in a heavy metal-polluted area. Data are the average (± SE) of six independent measurements. Amount (average ± SE) of metallic trace elements in the soil (mg/Kg): As = 298±80; Cd = 10±4; Cu = 459±88; Ni = 13±6, Pb = 7157±746; Zn = 14164±1460.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3646990&req=5

pone-0061932-g001: Amount of metallic trace elements (As, Cd, Cu, Ni, Pb and Zn) in shoots of H. incana.Plants were collected from different zones in a heavy metal-polluted area. Data are the average (± SE) of six independent measurements. Amount (average ± SE) of metallic trace elements in the soil (mg/Kg): As = 298±80; Cd = 10±4; Cu = 459±88; Ni = 13±6, Pb = 7157±746; Zn = 14164±1460.
Mentions: An exploration of the flora from mining sites in Oued El Himer region, located in the south of Oujda city (Eastern Morocco), was conducted in order to identify new species able to accumulate heavy metals in their shoots for a future phytoremediation project. The sites we studied have been heavily affected by lead mining and smelting activities, and soils are subject of a polymetallic contamination [24]. In these areas, lead concentrations in soils varied from 26 to 9479 mg.kg−1[24]. Plants were collected and leaf samples were analyzed by ICP-AES in order to quantify heavy metal contents. The Brassicaceae H. incana was particularly interesting because of its accumulation profile of toxic heavy metals in leaf tissue (Figure 1). In natural conditions, this species presented a high level of Pb in leaves ranging from 0.53 to 1.43 mg.g−1 DW with an average of 0.79 mg.g−1 DW (Figure 1). The other metals analyzed were present at lower concentration such as Cd or Zn with an average of 0.04 and 0.11 mg.g−1 DW respectively even if the concentrations of these metals were high in the different sampled soils [24]. These results show that H. incana seems to be highly specific for Pb accumulation in accordance to the contents of the different heavy metals analyzed. In order to confirm the accumulator trait observed in natural conditions and to avoid air-borne contamination such as dust deposits, H. incana plants were grown under controlled growth chamber conditions on four different soils collected in metalliferous mine spoils. These soils contained various amounts of total Pb (soil 1∶6973 mg.kg−1 DW; soil 2∶18626 mg.kg−1 DW; soil 3∶7531 mg.kg−1 DW; soil 4∶1577 mg.kg−1 DW, table 1). After 2 months of culture, Pb content was quantified in the shoots (Figure 2). The concentration of Pb in leaves was variable from a minimum of 0.43 mg.g−1 DW for plants grown on soil 1 to a maximum of 3.58 mg.g−1 DW for those grown on soil 3. These results confirmed the lead hyperaccumulator trait for H. incana. On the other hand, no correlation was observed between total Pb content in the different soils and Pb level in the plant tissues suggesting variations in the amount of bioavailable lead. CaCl2 and EDTA extractible fractions corresponding respectively to the mobile and the mobilisable fractions were quantified (Table 1). No correlation could be demonstrated between the Pb levels of the extractible fractions and those of the H. incana assimilated fraction.

Bottom Line: The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants.Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation.H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.

View Article: PubMed Central - PubMed

Affiliation: Institut de Recherche pour le Développement, Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes, Montpellier, France.

ABSTRACT
Lead is a heavy metal of particular concern with respect to environmental quality and health. The lack of plant species that accumulate and tolerate Pb is a limiting factor to understand the molecular mechanisms involved in Pb tolerance. In this study we identified Hirschfeldia incana, a Brassicaceae collected from metalliferous mine spoils in Morocco, as a Pb accumulator plant. H. incana exhibited high Pb accumulation in mine soils and in hydroponic cultures. Major Pb accumulation occurred in the roots and a part of Pb translocated from the roots to the shoots, even to the siliques. These findings demonstrated that H. incana is a Pb accumulator species. The expression of several candidate genes after Pb-exposure was measured by quantitative PCR and two of them, HiHMA4 and HiMT2a, coding respectively for a P1B-type ATPase and a metallothionein, were particularly induced by Pb-exposure in both roots and leaves. The functional characterization of HiHMA4 and HiMT2a was achieved using Arabidopsis T-DNA insertional mutants. Pb content and primary root growth analysis confirmed the role of these two genes in Pb tolerance and accumulation. H. incana could be considered as a good experimental model to identify genes involved in lead tolerance and accumulation in plants.

Show MeSH