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The well-known phenomenon of “the growth of all things depends on the sun†is based on the oxygen evolution photosynthesis that occurs in higher plants, algae, and cyanobacteria. These organisms fix CO2 through photosynthesis, convert solar energy into chemical energy, and at the same time cleave water molecules and release oxygen for biological respiration. Photosynthesis is the most important biochemical reaction on the earth and provides the biological basis for survival on Earth. Therefore, improving photosynthesis efficiency is of great significance to the effective use of solar energy, the promotion of agricultural production increase, and the acceleration of industrial CO2 emission reduction and resource utilization.
Photosynthesis is an extremely complex biochemical process. Based on the need for light, photosynthesis is artificially divided into photoreactions and dark reactions. In the past, research on photosynthesis was mainly focused on how to improve the utilization and conversion efficiency of light energy in light reaction, or increase the Rubisco carbon fixation efficiency of dark reaction key enzyme, and rarely considered how to increase the coupling efficiency of light reaction and dark reaction. In the actual physiological process, photosynthesis and dark reaction of photosynthesis are inseparable organic whole. The photoreaction produces energy (ATP) and reducing power (NADPH), whereas the dark reaction requires the consumption of ATP and NADPH in order to achieve reduction and fixation of CO2.
Institute of Microbiology, Institute of Microbiology, Chinese Academy of Sciences, Li Wei research group for the basic problem of the ATP generated by the light reaction can not meet the dark reaction carbon fixation energy requirements, according to the basic principles of the ATP and NADPH coupling in the photoreaction, from the cell's overall perspective, the photosynthesis The photoreaction and the dark reaction act as an organic whole, taking NADPH as an entry point to link the photosynthetic photoreaction with the dark reaction, and propose an introduction of NADPH consumption module, thereby breaking the inherent NADPH balance of the cell and effectively coupling the photoreaction with the dark reaction. To enhance the internal driving force of photoreaction, and to increase photosynthesis efficiency.
Researchers took photosynthetic oxygen-emitting bacteriobacter bacteria as a research model, and through the introduction of NADPH-dependent dehydrogenases, created an isopropanol biosynthetic pathway that consumes only NADPH without extra consumption of ATP (pictured). A series of photosynthetic physiology and biochemical analysis showed that after the introduction of NADPH consumption pathway, the cell growth was significantly accelerated, the photosynthesis efficiency was increased by about 50%, and the cell activity was higher. At the same time, it was found that the light saturation point of the cyanobacteria after modification was doubled, indicating that it can tolerate higher light intensity, which is of great significance in adapting to the drastic changes in light intensity in the natural world. This result indicates that the reduction-driven cellular global metabolic engineering strategy can more effectively increase the photosynthetic efficiency than the conventional single transformation of photoreaction or dark reaction. This strategy also has reference value for the transformation of photosynthesis of eukaryotes.
This work was published online in the Metabolic Engineering magazine on August 4th. The research was funded by the National Natural Science Foundation of China and the key deployment project of the Chinese Academy of Sciences, "Artificial Bioconversion of Carbon Dioxide". Associate researcher Zhou Jie and PhD student Zhang Fuliang are the co-first authors of the dissertation.
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