A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress

Abstract

Root exudates are thought to play an important role in plant-microbial interactions. In return for nutrition, soil bacteria can increase the bioavailability of soil nutrients. However, root exudates typically decrease in situations such as drought, calling into question the efficacy of solvation and bacteria-dependent mineral uptake in such stress. Here we tested the hypothesis of exudate-driven microbial priming on Cupressus saplings grown in forest soil in custom-made rhizotron boxes. A 1-month imposed drought and concomitant inoculations with a mix of Bacillus subtilis and Pseudomonas stutzeri, bacteria species isolated from the forest soil, were applied using factorial design. Direct bacteria counts and visualization by confocal microscopy showed that both bacteria associated with Cupressus Interestingly, root exudation rates increased 2.3-fold with bacteria under drought, as well as irrigation. Forty four metabolites in exudates were significantly different in concentration between irrigated and drought trees, including phenolic acid compounds and quinate. When adding these metabolites as carbon and nitrogen sources to bacterial cultures of both bacterial species, 8 of 9 metabolites stimulated bacterial growth. Importantly, soil phosphorous bioavailability was maintained only in inoculated trees, mitigating drought-induced decrease in leaf phosphorus and iron. Our observations of increased root exudation rate when drought and inoculation regimes were combined, support the idea of root recruitment of beneficial bacteria, especially under water stress.

Data availability

Data Sharing DeclarationAll data related to the study are reported in the manuscript and Supplementary Information. Source Data files 1-6 are included in the submission.

Article and author information

Author details

  1. Yaara Oppenheimer-Shaanan

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-7005-3074
  2. Gilad Jakoby

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
  3. Maya L Starr

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
  4. Romiel Karliner

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
  5. Gal Eilon

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
  6. Maxim Itkin

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1348-2814
  7. Sergey Malitsky

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    Competing interests
    The authors declare that no competing interests exist.
  8. Tamir Klein

    Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
    For correspondence
    tamir.klein@weizmann.ac.il
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3882-8845

Funding

Edith and Natan Goldenberg Career Development Chair

  • Tamir Klein

Mary and Tom Beck (Canadian Center for Alternative Energy Research)

  • Tamir Klein

Larson Charitable Foundation New Scientist Fund

  • Tamir Klein

Angel mFaivovich Foundation for Ecological Research

  • Tamir Klein

Yotam project

  • Tamir Klein

Dana and Yossie Hollander

  • Tamir Klein

Estate of Emile Mimran

  • Tamir Klein

Estate of Helen Nichunsky

  • Tamir Klein

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Meredith C Schuman, University of Zurich, Switzerland

Publication history

  1. Received: April 22, 2022
  2. Accepted: July 17, 2022
  3. Accepted Manuscript published: July 20, 2022 (version 1)

Copyright

© 2022, Oppenheimer-Shaanan et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Yaara Oppenheimer-Shaanan
  2. Gilad Jakoby
  3. Maya L Starr
  4. Romiel Karliner
  5. Gal Eilon
  6. Maxim Itkin
  7. Sergey Malitsky
  8. Tamir Klein
(2022)
A dynamic rhizosphere interplay between tree roots and soil bacteria under drought stress
eLife 11:e79679.
https://doi.org/10.7554/eLife.79679

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