Enhanced rubisco enzyme engineering for improved crop nitrogen and resource use efficiency

Overview

This research program targets improvements in plant growth and resource use efficiency by enhancing the carboxylation properties of Rubisco, the primary photosynthetic enzyme responsible for fixing atmospheric CO2 into plant biomass. Rubisco's catalytic inefficiencies represent a major rate-limiting step in photosynthesis, requiring plants to commit 25-60% of their leaf soluble protein and 15-30% of leaf nitrogen to produce sufficient enzyme to support growth. By improving Rubisco performance, crops could achieve higher productivity with reduced nitrogen inputs, offering significant benefits for sustainable agriculture and input cost reduction.

The approach is inspired by natural CO2-concentrating mechanisms found in C4 plants, where Rubisco has evolved faster turnover rates and operates at near-saturating CO2 levels. C4 plants require less Rubisco and demonstrate significantly higher nitrogen use efficiencies than C3 plants. Additionally, elevated CO2 growth conditions naturally reduce Rubisco production through source-sink metabolic regulation, suggesting that enhanced Rubisco carboxylation could emulate these benefits in standard atmospheric conditions.

Technical specifications

Research approach:

• Laboratory evolution of Rubisco to identify amino acid changes that enhance carbon assimilation rates
• Generation of transplastomic tobacco germplasm expressing improved Rubisco variants
• Controlled glasshouse trials with varying nitrogen treatments
• Comparative analysis of photosynthesis, growth, and nitrogen use efficiency metrics
• Single amino acid modifications already identified that increase carbon assimilation by up to 25% in C3 crops and 30% in C4 crops

Key benefits for agriculture:

• Reduced nitrogen fertilizer requirements through improved nitrogen use efficiency
• Enhanced carbon fixation rates supporting higher biomass production
• Potential improvements in water and light use efficiency as secondary benefits
• Applicable to both C3 and C4 crop species

Technology readiness level

The project builds on validated laboratory-evolved Rubisco variants with demonstrated improvements in carbon assimilation rates. The current phase focuses on greenhouse-based validation of nitrogen use efficiency in transplastomic tobacco expressing the enhanced Rubisco. This represents an intermediate stage between laboratory proof-of-concept and field validation, with the goal of demonstrating agronomic benefits under nitrogen-limited growth conditions before advancing to crop species translation.