Rubisco variants are at the center of new research from KTH Royal Institute of Technology in Sweden, where scientists built and assessed roughly 15,000 genetically modified versions of a bacterial form of the enzyme that captures carbon dioxide. The study, published in Science Advances, seeks to inform strategies for engineering more efficient photosynthesis in support of climate-resilient crops.
Rubisco drives carbon fixation in bacteria and plants, but it is slow and can mistakenly react with oxygen. That misfire forces cells to spend energy processing byproducts, which drags on growth. Limiting this penalty has long been a goal for researchers hoping to accelerate plant growth and improve yields under changing climate conditions.
The team worked with a bacterial enzyme because its simpler architecture enables high-throughput production and testing. According to Paul Hudson, a professor of systems biology at KTH, the objective was to identify versions that support robust bacterial growth, establishing principles that could later be applied to plant enzymes and plant cells.
Although the experiments centered on a bacterial Rubisco, the resulting catalog of both successful and unsuccessful mutations provides a potential roadmap for designing improved enzymes. The dataset may also help refine computational tools that predict how changes to Rubisco influence performance. Any translation of these lessons to plant Rubisco will require additional testing in plant cells and whole plants.
Rubisco variants and implications for climate-resilient crops
Technological achievement
Using a custom high-throughput screening system, each candidate carried a unique DNA barcode, enabling the researchers to track the performance of thousands of Rubisco variants at once, including single and combined mutations. Hudson said the approach could be adapted to probe other metabolic enzymes.
The investigators selected bacterial Rubisco for its ease of large-scale expression and evaluation, which allows rapid identification of design rules that can later be examined in plant systems. Some bacterial form II Rubiscos process carbon dioxide more quickly than plant enzymes, Hudson noted, but they more readily catalyze the oxygenation reaction. The team aimed to push faster variants to be even faster, or to curb oxygenation while keeping high carboxylation rates.
New insights
Two leading candidates showed lower reactivity with oxygen while maintaining useful carbon-dioxide turnover, though both exhibited trade-offs that limited overall efficiency. Mutations that were beneficial on their own often lost their advantage when combined.
The researchers also benchmarked several computational models that predict the impacts of mutations on Rubisco. The tools performed better for single changes than for combinations, underscoring the complexity of the enzyme’s behavior.
According to the team, the findings highlight that Rubisco mutation effects are difficult to forecast without extensive experimental data. Next steps include further reducing oxygenation in promising variants and dissecting which structural elements drive selectivity for carbon dioxide. Researchers are also testing engineered enzymes in plant cells and in cyanobacteria that synthesize useful chemicals through an EU-funded project.
The team worked with a bacterial enzyme because its simpler architecture enables high-throughput production and testing. According to Paul Hudson, a professor of systems biology at KTH Royal Institute of Technology, the objective was to identify versions that support robust bacterial growth, establishing principles that could later be applied to plant enzymes and plant cells.
Any translation of these lessons to plant Rubisco will require additional testing in plant cells and whole plants, a step that could ultimately intersect with efforts to boost yields and resilience in major crops alongside innovations such as ‘switchable’ biofertilizers.