Rubisco is evolving for improved catalytic efficiency and CO₂ assimilation in plants

Area of Science:

• Biochemistry
• Evolutionary Biology
• Plant Science

Background:

• Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is crucial for carbon fixation in photosynthesis.
• Rubisco's catalytic inefficiency has prompted questions about its evolutionary adaptability.

Purpose of the Study:

• To investigate the molecular and kinetic evolution of Form I Rubisco in angiosperms.
• To determine the evolutionary trajectory of Rubisco's catalytic efficiency and CO2 assimilation.

Main Methods:

• Phylogenetic analysis of the Rubisco gene (rbcL).
• Examination of molecular evolution rates.
• Assessment of kinetic properties related to CO2/O2 specificity and turnover.

Main Results:

• The rbcL gene evolves exceptionally slowly, with one nucleotide substitution every 0.9 million years.
• Despite slow evolution, Rubisco has continuously improved its CO2/O2 specificity, carboxylase turnover, and carboxylation efficiency.
• Rubisco evolution correlates with enhanced leaf-level CO2 assimilation.

Conclusions:

• Rubisco has undergone slow but consistent evolutionary adaptation to improve its catalytic efficiency.
• These adaptations have led to significant improvements in CO2 assimilation in plants over evolutionary time.