Synthetic biology approaches to improve Rubisco carboxylation efficiency in C₃ Plants: Direct and Indirect Strategies

Food security remains a pressing issue due to the growing global population and climate change, including the global warming along with increased atmospheric CO₂ levels, which can negatively impact C₃ crop yields. A major limitation in C₃ plants is the inefficiency of Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) due to its low carboxylation activity and competing oxygenase activity. Improving Rubisco efficiency in C₃ plants is thus essential for improving photosynthetic performance. Recent advances in synthetic biology have introduced promising strategies to overcome these limitations. This review highlights the latest synthetic biology and gene transformation techniques aimed at optimizing Rubsico carboxylation efficiency. Next, direct approaches such as engineering Rubisco subunits by replacing plant Rubisco with proteins from other organisms are discussed. Additionally, indirect strategies involve modifications of Rubisco-interacting proteins and adjustment of Rubisco environment. We explore CO₂-concentrating mechanisms (CCMs) based on pyrenoids and carboxysomes, which increase local CO₂ concentrations around Rubisco thus favouring the carboxylation reaction. Lastly, photorespiratory bypasses are also covered in this review.