Proof that chloroplasts can host active Nitrogenase

The generation of nitrogen fixing crops is a challenge that could lead to a new agricultural “green” revolution by reducing the need for commercial fertilizers. Its prohibitive price in developing countries are responsible for very low yields of crops that lead to hunger and poverty. On the other hand, their current extensive use in developed countries has many undesirable consequences for the environment. The enzyme responsible for biological nitrogen fixation, nitrogenase, has very low tolerance for oxygen, and thus, the engineering of its biosynthetic pathway in plants has had to deal with strategies to isolate it from photosynthesis, the process responsible for most oxygen production within a plant cell.

Researchers from the Caro and Rubio labs, at the CBGP (UPM-INIA) report the use of synthetic biology tools to optimize the production of nitrogenase Fe protein (NifH) in the chloroplasts of tobacco plants. Importantly, NifH purified from tobacco chloroplasts was active when purified at the end of the dark period of growth. These results support the suitability of chloroplasts of photosynthetically active plants to host functional nitrogenase proteins, paving the way for future studies in the engineering of nitrogen fixation in higher plant plastids and describing an optimization pipeline that could also be used in other organisms and in the engineering of new metabolic pathways in plastids.

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