Improvement of photosynthesis in changing environment: approaches, achievements and prospects

Photosynthesis is responsible for sustained plant productivity and ensures food supply. The change in global climatic patterns affects photosynthesis that subsequently reduces plant yield and poses threat to food security. Photosynthesis relies on a dual nature enzyme ribulose 1, 5 bisphosphate carboxylase oxygenase (Rubisco), which can fix CO₂ as well as O₂. The fixation rate of CO₂ to O₂ depends upon the relative concentration of CO₂ inside chloroplast. Higher level of CO₂ results in improved photosynthesis, however, its concentration depends upon environmental conditions. Under adverse climate conditions, the CO₂ level drops down that leads to increased oxygenation which impedes the photosynthesis and reduces plant productivity. The impact is more significant and apparent specifically in C₃ plants. Attempts have been made to address the loss in photosynthesis and multiple strategies have been adapted to date that focus on improvement of photosynthesis in C₃ plants. In this review, we have discussed the multiple strategies being employed by different researchers to date for improvement of photosynthesis. The strategies discussed in this review include: improving the performance of Rubisco, engineering CO₂-concentrating mechanism of C₄ photosynthesis into C₃ species, transformation of bicarbonate transporters from cyanobacteria into chloroplasts of C₃ plants, and establishment of photorespiratory bypasses to catabolise toxic glycolate in shortest possible pathway.