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Tracking nickel-adaptive biomarkers in Pisolithus albus from New Caledonia using a transcriptomic approach

Authors

  • CLARISSE MAJOREL,

    1. IRD, UMR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, New Caledonia
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  • LAURE HANNIBAL,

    1. IRD, UMR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, New Caledonia
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  • MARIE-ESTELLE SOUPE,

    1. IRD, UMR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, New Caledonia
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  • FABIAN CARRICONDE,

    1. Institut Agronomique néo-Calédonien (IAC), Axe 2 ‘Diversités biologique et fonctionnelle des écosystèmes terrestres’, Nouméa IRD research centre – BPA5, 98800 Nouméa, New Caledonia
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  • MARC DUCOUSSO,

    1. Institut Agronomique néo-Calédonien (IAC), Axe 2 ‘Diversités biologique et fonctionnelle des écosystèmes terrestres’, Nouméa IRD research centre – BPA5, 98800 Nouméa, New Caledonia
    2. CIRAD, UMR LSTM, TA A-82/J Campus International de Baillarguet, 34398 Montpellier Cedex 5
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  • MICHEL LEBRUN,

    1. Université Montpellier 2, UMR28 LSTM, TA A-82/J Campus International de Baillarguet, 34398 Montpellier Cedex 5, France
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  • PHILIPPE JOURAND

    1. IRD, UMR040 LSTM, Centre IRD, BPA5, Promenade Roger Laroque, 98848 Nouméa Cedex, New Caledonia
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Clarisse Majorel, Fax: +687 26 43 26; E-mail: clarisse.majorel@ird.fr

Abstract

The fungus Pisolithus albus forms ectomycorrhizal (ECM) associations with plants growing on extreme ultramafic soils, which are naturally rich in heavy metals such as nickel. Both nickel-tolerant and nickel-sensitive isolates of P. albus are found in ultramafic soils in New Caledonia, a biodiversity hotspot in the Southwest Pacific. The aim of this work was to monitor the expression of genes involved in the specific molecular response to nickel in a nickel-tolerant P. albus isolate. We used pyrosequencing and quantitative polymerase chain reaction (qPCR) approaches to investigate and compare the transcriptomes of the nickel-tolerant isolate MD06-337 in the presence and absence of nickel. A total of 1 071 375 sequencing reads were assembled to infer expression patterns of 19 518 putative genes. Comparison of expression levels revealed that 30% of the identified genes were modulated by nickel treatment. The genes, for which expression was induced most markedly by nickel, encoded products that were putatively involved in a variety of biological functions, such as the modification of cellular components (53%), regulation of biological processes (27%) and molecular functions (20%). The 10 genes that pyrosequencing analysis indicated were induced the most by nickel were characterized further by qPCR analysis of both nickel-tolerant and nickel-sensitive P. albus isolates. Five of these genes were expressed exclusively in nickel-tolerant isolates as well as in ECM samples in situ, which identified them as potential biomarkers for nickel tolerance in this species. These results clearly suggest a positive transcriptomic response of the fungus to nickel-rich environments. The presence of both nickel-tolerant and nickel-sensitive fungal phenotypes in ultramafic soils might reflect environment-dependent phenotypic responses to variations in the effective concentrations of nickel in heterogeneous ultramafic habitats.

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