Early transcriptional responses to mercury: a role for ethylene in mercury-induced stress

Authors

  • M. Belén Montero-Palmero,

    1. Laboratorio de Fisiología Vegetal, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
    2. Laboratorio de Fisiología Vegetal, Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Toledo, Spain
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  • Amanda Martín-Barranco,

    1. Laboratorio de Fisiología Vegetal, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
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  • Carolina Escobar,

    1. Laboratorio de Fisiología Vegetal, Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Toledo, Spain
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    • These authors contributed equally to this work.

  • Luis E. Hernández

    Corresponding author
    1. Laboratorio de Fisiología Vegetal, Departamento de Biología, Universidad Autónoma de Madrid, Madrid, Spain
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    • These authors contributed equally to this work.


Summary

  • Understanding the cellular mechanisms of plant tolerance to mercury (Hg) is important for developing phytoremediation strategies of Hg-contaminated soils. The early responses of alfalfa (Medicago sativa) seedlings to Hg were studied using transcriptomics analysis.
  • A Medicago truncatula microarray was hybridized with high-quality root RNA from M. sativa treated with 3 μM Hg for 3, 6 and 24 h. The transcriptional pattern data were complementary to the measurements of root growth inhibition, lipid peroxidation, hydrogen peroxide (H2O2) accumulation and NADPH-oxidase activity as stress indexes.
  • Of 559 differentially expressed genes (DEGs), 91% were up-regulated. The majority of DEGs were shared between the 3 and 6 h (60%) time points, including the ‘stress’, ‘secondary metabolism’ and ‘hormone metabolism’ functional categories. Genes from ethylene metabolism and signalling were highly represented, suggesting that this phytohormone may be relevant for metal perception and homeostasis.
  • Ethylene-insensitive alfalfa seedlings preincubated with the ethylene signalling inhibitor 1-methylcyclopronene and Arabidopsis thaliana ein2-5 mutants confirmed that ethylene participates in the early perception of Hg stress. It modulates root growth inhibition, NADPH-oxidase activity and Hg-induced apoplastic H2O2 accumulation. Therefore, ethylene signalling attenuation could be useful in future phytotechnological applications to ameliorate stress symptoms in Hg-polluted plants.

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