Abstract
While classical breeding traits have focussed on above-ground tissues, it is becoming clear that underground aspects of plant life are a hidden treasure of tools applicable for resilient crop production. Plants of the legume family develop specialized organs, called nodules, which serve as hosts for Rhizobium bacteroids. A highly specialized symbiotic relationship exists deep inside the nodules. In exchange for carbohydrates, host-specific rhizobia bacteroids can assimilate nitrogen from the air and fix it into a form that can be used by plants in a process known as biological nitrogen fixation. While we understand certain aspects of how this inter-species relationship is established, the exact biochemistry of this exchange remains dogmatic. In their recent work, Christen and colleagues (Flores-Tinoco etal, 2020) challenge the current model of nitrogen exchange and argue that that an expanded model is needed to fit experimental findings related to nitrogen fixation. The authors perform an elegant set of experiments and highlight that rather than a single-way flow of nitrogen, the N-fixing process is in fact an elaborate metabolic exchange between the nodule-dwelling bacteroids and the host plant. Importantly, this work provides an updated theoretical framework with the "catchy" name CATCH-N which delivers up to 25% higher yields of nitrogen than classical models and is suitable for rational bioengineering and optimization of nitrogen fixation in microorganisms.
Highlights
While classical breeding traits have focussed on above-ground tissues, it is becoming clear that underground aspects of plant life are a hidden treasure of tools applicable for resilient crop production
In the emerging age of biotechnological solutions, one of the most intriguing features for agricultural improvement is to modify the crop of interest to either facilitate biological nitrogen fixation directly, or establish microbial relationships with natural or modified nitrogenfixing bacteria that would result in a net nitrogen gain for the plant
Our current model of nutrient exchange in rhizobia–legume symbiosis postulates that, in exchange for nitrogen, the plant provides C4-dicarboxylic acids such as succinate. These are metabolized through the tri-carboxylic acid (TCA) cycle to generate ATP and reduction equivalents needed for the nitrogenase reaction (Hoffman et al, 2014)
Summary
While classical breeding traits have focussed on above-ground tissues, it is becoming clear that underground aspects of plant life are a hidden treasure of tools applicable for resilient crop production. The prospect of implementing nitrogen fixation into non-legume crops has fascinated researchers and breeders alike for centuries as this would decrease the demand for artificial fertilization. To catalyse atmospheric nitrogen fixation, rhizobia use a specific enzyme termed nitrogenase, which is able to catalyse formation of ammonium (Hoffman et al, 2014).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
