Researchers from the University of Sydney and the Australian National University have developed a groundbreaking method to enhance photosynthesis in crops, potentially increasing yields for essential staples like wheat and rice while reducing their reliance on water and nitrogen. The innovative approach involves engineering tiny compartments, which house the enzyme Rubisco, crucial for carbon fixation during photosynthesis.
For the past five years, the team, led by Associate Professor Yu Heng Lau and Professor Spencer Whitney, has focused on a central challenge in plant biology: improving the efficiency of carbon fixation. Their findings, published in Nature Communications, reveal that by creating nanoscale “offices” for Rubisco, scientists can optimize its effectiveness in agricultural settings.
Rubisco is a fundamental enzyme found in plants, vital for converting carbon dioxide into organic compounds. Despite its importance, it is notoriously inefficient. Lead researcher Dr. Taylor Szyszka noted, “Rubisco is very slow and can mistakenly react with oxygen instead of CO2, triggering a process that wastes energy and resources.” This inefficiency leads to significant energy and nitrogen expenditure, as crops such as wheat and rice produce Rubisco in large quantities—sometimes constituting up to 50 percent of soluble protein in leaves.
The research team drew inspiration from nature, where some microorganisms, including algae and cyanobacteria, have developed specialized compartments that enhance Rubisco’s functionality. These compartments serve to concentrate carbon dioxide, allowing the enzyme to operate more effectively. Previous attempts to introduce similar systems into crops faced challenges due to their complexity and the need for multiple genes to work in harmony.
To overcome these hurdles, the Lau and Whitney team opted for a simpler solution using encapsulins. These bacterial protein cages can be constructed with just one gene, akin to assembling Lego blocks. To facilitate the incorporation of Rubisco, the researchers attached a short “address tag” of 14 amino acids to the enzyme, guiding it to its destination within the encapsulin.
The team experimented with three varieties of Rubisco, including one from a plant and two from bacteria. They discovered that the order of assembly was crucial; for complex forms of the enzyme, Rubisco must be built first before encasing it in the protein shell. “Rubisco didn’t assemble properly when trying to do both at once,” noted PhD candidate Davin Wijaya, who co-led the study.
Another significant advantage of the encapsulin system is its modularity. Unlike carboxysomes, which can only accommodate their native Rubisco, the encapsulin framework can incorporate various types of Rubisco. Dr. Szyszka emphasized, “Most excitingly, we found the pores in the encapsulin shell allow for the entry and exit of Rubisco’s substrate and products.”
While the current research serves as a proof of concept, the team acknowledges that additional components are necessary to provide Rubisco with an optimal working environment. 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 stated.
If successful, this innovative approach to carbon fixation could lead to crops that generate higher yields with less water and nitrogen fertilizer. As global food systems face increasing pressures from climate change and population growth, the potential benefits of this research could be significant for sustainable agriculture.
The study, titled “Reprogramming encapsulins into modular carbon-fixing nanocompartments,” was supported by funding from the Australian Research Council, with no competing interests declared by the authors.
