The Integration of Algal Carbon Concentration Mechanism Components into Tobacco Chloroplasts Increases Photosynthetic Efficiency and Biomass

Increasing the productivity of crops is a major challenge in agricultural research. Given that photosynthetic carbon assimilation is necessary for plant growth, enhancing the efficiency of photosynthesis is one strategy to boost agricultural productivity. The authors attempted to increase the photosynthetic efficiency and biomass of tobacco plants by expressing individual components of the Chlamydomonas reinhardtii carbon concentration mechanism (CCM) and integrating them into the chloroplast. Independent transgenic varieties are generated accumulating the carbonic anhydrase CAH3 in the thylakoid lumen or the bicarbonate transporter LCIA in the inner chloroplast membrane. Independent homozygous transgenic lines showed enhanced CO2 uptake rates (up to 15%), increased photosystem II efficiency (by up to 18%), and chlorophyll content (up to 19%). Transgenic lines produced more shoot biomass than wild-type and azygous controls, and accumulated more carbohydrate and amino acids, reflecting the higher rate of photosynthetic CO2 fixation. These data demonstrate that individual algal CCM components can be integrated into C-3 plants to increase biomass, suggesting that transgenic lines combining multiple CCM components could further increase the productivity and yield of C-3 crops.