Two key components of the enzyme nitrogenase, which converts atmospheric nitrogen to ammonia, have been produced in a major food crop

Researchers from the Center for Plant Biotechnology and Genomics (CBGP) – a joint research center established by the Technical University of Madrid (UPM) and the National Institute for Agricultural and Food Research and Technology (INIA/CSIC) – have collaborated with the University of Lleida-Agrotecnio Center and the Catalan Institution for Research and Advanced Studies (ICREA) to produce the first transgenic cereals that express two key components of nitrogenase, the enzyme which fixes atmospheric nitrogen by converting it into ammonia.

 

  1. Researchers from the Center for Plant Biotechnology and Genomics (CBGP) – a joint research center established by the Technical University of Madrid (UPM) and the National Institute for Agricultural and Food Research and Technology (INIA/CSIC) – have collaborated with the University of Lleida-Agrotecnio Center and the Catalan Institution for Research and Advanced Studies (ICREA) to produce the first transgenic cereals that express two key components of nitrogenase, the enzyme which fixes atmospheric nitrogen by converting it into ammonia.
  2. Each component was produced in a separate transgenic plant line and was shown to be biologically active in vitro or in living plants.
  3. These transgenic plants cannot yet fix their own nitrogen because additional components are needed to reconstruct the complete nitrogenase enzyme, but the work is nevertheless groundbreaking because it demonstrates for the first time that it is possible to express these highly oxygen sensitive proteins stably in plants, and that the proteins retain their activities.
  4. Research on nitrogenase expression usually involves laboratory model plants. By focusing instead on rice, a major staple crop that provides the main or only source of calories for more than 2.5 billion people in developing countries, the significance and impact of the results is substantially enhanced.
  5. This achievement represents a major step towards the development of cereal crops that fix their own nitrogen, which would dramatically reduce fertilizer input requirements.
  6. The work has been published in two high-ranking journals: Communications Biology and American Chemical Society Synthetic Biology.

Madrid-Lleida, Spain, October  06/10/2022.

Crops require nitrogen for growth and productivity because it is a major component of DNA, proteins, chlorophyll, and energy-storage molecules such as ATP. Most crops depend on supplies of nitrate and ammonium from industrial synthetic fertilizers, but more than half of these inputs remain unassimilated, spilling over or leaching into rivers and lakes as a major source of pollution.

Leguminous crops such as peas and beans harbour bacteria that convert nitrogen gas directly into ammonia using an enzyme called nitrogenase. This process is known as biological nitrogen fixation. The introduction of nitrogenase genes into crop plants would provide the machinery needed to fix nitrogen independently. However, the process is extremely complex because many different individual proteins are required not only as the direct structural components of nitrogenase, but also accessory proteins needed for its assembly and the provision of energy. The major protein components are also extremely oxygen sensitive. The researchers overcame this critical bottleneck by producing functional dinitrogenase reductase (Fe protein, NifH) and the nitrogenase cofactor maturase (NifB) in separate transgenic rice lines. The importance of this work is explained by the project’s principal investigator, Dr Luis Rubio: “This is a major bioengineering advance as it tears down two technical roadblocks and shows the path to make nitrogen-fixing cereals.” The achievement removes one of the major constraints hindering biological nitrogen fixation in crops and sets the stage for the assembly of a complete and functional nitrogenase complex in plants. Further work to establish plants containing the full nitrogenase would have a lasting impact on global food security, as elaborated by Dr Paul Christou, ICREA research professor and project lead at the University of Lleida-Agrotecnio Center: “One of the major impacts of the work in the long term will be in low- and middle-income countries, which cannot afford expensive nitrogen fertilizers.” The work is part of a research program funded by a grant from the Bill & Melinda Gates Foundation.

Further information

Luis Rubio, Centro de Biotecnología y Genómica de Plantas (UPM - INIA/CSIC): This email address is being protected from spambots. You need JavaScript enabled to view it. Paul Christou, ICREA, Universidad de Lleida-Agrotecnio: This email address is being protected from spambots. You need JavaScript enabled to view it.

Baysal, C., Burén, S., He, W., Jiang, X., Capell, T., Rubio, L.M., Christou, P. 2022. Functional expression of the nitrogenase Fe protein in transgenic rice. Communications Biology 5, 1–9. DOI: 10.1038/s42003-022-03921-9

He, W., Burén, S., Baysal, C., Jiang, X., Capell, T., Christou, P., Rubio, L.M. 2022. Nitrogenase Cofactor Maturase NifB Isolated from Transgenic Rice is Active in FeMo-co Synthesis. ACS Synthetic Biology. DOI: 10.1021/acssynbio.2c00194

 


 

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