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Engineered plant control of associative nitrogen fixation
Timothy L Haskett1, Ponraj Paramasivan2, Marta D Mendes1
1Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
Summary
Researchers engineered barley to produce a signal, enabling nitrogen-fixing bacteria to activate their nitrogenase gene only on the plant
Area of Science:
- Agricultural Microbiology
- Plant-Bacterial Symbiosis
- Synthetic Biology
Background:
- Nitrogen (N) fixation via cereal-diazotrophic bacteria symbiosis offers sustainable agriculture.
- Previous work established transkingdom signaling using plant-produced rhizopine to control bacterial gene expression.
Purpose of the Study:
- To engineer a synthetic symbiosis for controlled biological nitrogen fixation.
- To enhance bacterial sensitivity to plant-derived signals for precise gene regulation.
Main Methods:
- Developed a homozygous rhizopine-producing (RhiP) barley line.
- Created a hybrid rhizopine uptake system for Azorhizobium caulinodans ORS571 (Ac), increasing sensitivity 103-fold.
- Established rhizopine-dependent transcriptional control of nifA and rpoN genes.
Main Results:
- Achieved tight, rhizopine-dependent control of nitrogenase expression and activity in vitro and in situ.
- Demonstrated specific activation of nitrogenase on RhiP barley roots, not on wild-type plants.
- Observed suboptimally effective, but specific, in situ nitrogenase activity.
Conclusions:
- This study is a key step towards synthetic plant-controlled N2-fixing symbioses.
- Engineered bacteria fix nitrogen only on target host plants, preventing off-target interactions.
- Enables precise control over biological nitrogen fixation in agricultural settings.
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