Nitroblast

The production of food crops is heavily dependent on fertilizers, which provide essential nitrogen to plants. However, the manufacturing and application of fertilizers have a considerable negative impact on the environment, contributing to both CO2 emissions and nitrogen pollution. The iGEM project 2024 sought to address this challenge by engineering eukaryotic organisms (plants) capable of fixing nitrogen independently, eliminating the need for nitrogen-based fertilizers. To achieve this goal, we leveraged the recent discovery of the nitrogen-fixing organelle known as UCYN-A, or nitroplast. This organelle evolved from a bacterial endosymbiont residing within the marine alga Braarudosphaera bigelowii, and is now fully reliant on proteins imported from B. bigelowii. Concretely, iGEM team 2024 worked on designing endosymbiosis as a strategy to confer nitrogen fixing capability to other eukaryotes, starting with yeast and algae, and paving a way for doing so in plants.

As with other organelles such as mitochondria and chloroplasts, most of the proteins necessary for the nitroplast to function are encoded by the nuclear genome and need to be imported. One of the key iGEM 2024 findings is that of a UCYN-A transit peptide (uTP) in the C-terminal region of proteins expressed by B. bigelowii and imported into the nitroplast. The uTP consists of two conserved motifs with a fixed spacing, followed by a combination of several motifs which we hypothesize may contribute to suborganellar localization. We envision continuing this line of research and characterizing the newly identified uTP and its interaction partners, combining wet and dry lab techniques.