Stable isotope labelling reveals that NaCl stress decreases the production of Ensifer (Sinorhizobium) arboris lipochitooligosaccharide signalling molecules

Authors

  • Petri Penttinen,

    Corresponding author
    1. Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
    • Correspondence: Petri Penttinen, Department of Food and Environmental Sciences, University of Helsinki, PO Box 56 (Viikinkaari 9), FI-00014 Helsinki, Finland.

      Tel.: +358 9 19159280;

      fax: +358 9 19159322;

      e-mail: petri.penttinen@helsinki.fi

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  • Leena A. Räsänen,

    1. Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
    Current affiliation:
    1. Department of Agronomical Microbiology, Institute of Soil Science and Plant Cultivation, State Research Institute, Puławy, Poland
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  • Gilles Lortet,

    1. Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
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  • Kristina Lindström

    1. Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
    Current affiliation:
    1. Department of Environmental Sciences, University of Helsinki, Helsinki, Finland
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Abstract

Ensifer (Sinorhizobium) arboris is a symbiont of salt-tolerant leguminous trees in the genera Acacia and Prosopis that are utilized in the prevention of soil erosion and desertification and in phytoremediation of salinized soil. Signalling between the plant and the rhizobia is essential for the formation of effective symbiosis that increases the success of reclaiming saline sites. We assessed the effect of salt stress on the growth and the production of lipochitooligosaccharide signalling molecules (LCOs) of S. arboris HAMBI 2361, an LCO-overproducing derivative of the S. arboris type strain HAMBI 1552. The strain tolerated NaCl up to 750 mM. To obtain both qualitative and quantitative information on the LCO production under salt stress, we devised a method where LCOs were differentially labelled by stable isotopes of nitrogen, 14N and 15N, and analysed by mass spectrometry. Under control conditions, the strain produced altogether 27 structural LCO variants. In 380 mM NaCl, 13 LCO variants were produced in detectable amounts, and six of these were reliably quantified, ranging from one-tenth to one-third of the non-stressed one.

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