Researchers from the University of Sydney and the Australian National University have developed a groundbreaking method to enhance photosynthesis in crops like wheat and rice. This innovative approach could significantly increase crop yields while reducing water and nitrogen usage, addressing critical challenges in global food production.
Over a five-year period, the team, led by Associate Professor Yu Heng Lau and Professor Spencer Whitney, focused on improving the efficiency of the enzyme Rubisco, which plays a crucial role in carbon fixation during photosynthesis. Their findings were published in Nature Communications.
Rubisco is essential for converting carbon dioxide into energy, yet it is notably inefficient. According to Dr. Taylor Szyszka from the ARC Centre of Excellence in Synthetic Biology, “Rubisco is very slow and can mistakenly react with oxygen instead of CO2, leading to a wasteful process.” This inefficiency prompts many vital crops to produce excessive Rubisco, consuming significant energy and nitrogen resources. In some instances, up to 50 percent of soluble protein in leaves is comprised of this single enzyme, creating a substantial bottleneck in plant growth.
To overcome this limitation, researchers drew inspiration from natural systems. Certain microorganisms, such as algae and cyanobacteria, utilize specialized compartments to house Rubisco, allowing for concentrated CO2 supply. This design enables the enzyme to function more effectively. However, replicating these natural systems in crops has proven complex due to the need for multiple genes to work in harmony.
The research team opted for a different strategy by using encapsulins—simple bacterial protein cages requiring just one gene for assembly. This modular approach enables the encapsulins to package various Rubisco types, unlike carboxysomes, which can only accommodate their native Rubisco.
The innovative method involves adding a short “address tag” of 14 amino acids to Rubisco, guiding it to its designated compartment within the encapsulin. The researchers tested three varieties of Rubisco: one from a plant and two from bacteria. Their findings indicate that the timing of the assembly process is crucial. For more complex forms of Rubisco, it was necessary to construct the enzyme first before encasing it within the protein shell.
Davin Wijaya, a PhD candidate at the Australian National University and co-lead on the study, shared insights on the assembly process, stating, “Rubisco didn’t assemble properly when trying to do both at once.” This discovery highlights the precision required in engineering these systems for optimal performance.
The encapsulin system also offers a significant advantage: the pores in the shell facilitate the entry and exit of Rubisco’s substrates and products, enhancing its efficiency. While the current research serves as a proof of concept, the team plans to integrate additional components to create a high-performance environment for Rubisco.
Early-stage plant experiments are already underway at the Australian National University. “We know we can produce encapsulins in bacteria or yeast; making them in plants is the next sensible step. Our preliminary results look promising,” Wijaya remarked.
If successfully implemented, this enhanced CO2-fixing technology could lead to crops that yield more food while using less water and nitrogen fertilizer. This development is particularly crucial as climate change and population growth continue to exert pressure on global food systems.
The research, titled “Reprogramming encapsulins into modular carbon-fixing nanocompartments,” represents a significant advancement in synthetic biology and agricultural science. The authors declare no competing interests, and funding for the study was provided by the Australian Research Council.
