C2 photosynthesis: a promising route towards crop improvement?

Abstract

C₂ photosynthesis is a carbon concentrating mechanism that can increase net CO₂ assimilation by capturing, concentrating and re-assimilating CO₂ released by photorespiration. Empirical and modelling studies indicate that C₂ plants assimilate more carbon than C₃ plants under high temperature, bright light, and low CO₂ conditions. I argue that engineering C₂ photosynthesis into C₃ crops is a promising approach to improve photosynthetic performance under these - and temporally heterogeneous - environments, and review the modifications that may re-create a C₂ phenotype in C₃ plants. Although a C₂ engineering program would encounter many of the same challenges faced by C₄ engineering programmes, the simpler leaf anatomical requirements make C₂ engineering a feasible approach to improve crops in the medium term.

Keywords: C2 photosynthesis; C3-C4 intermediate; bundle sheath cells; carbon concentrating mechanism; crop improvement; food security; glycine shuttle; photorespiratory CO2 pump.