Project Description
Plants show diversity in the form of C4 and C3 type of photosynthesis to assimilate free carbon dioxide to synthesize macromolecules for sustained life. RUBISCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is a key enzyme that fixes CO2 in the chloroplasts of photosynthetic organisms by its carboxylase activity. In addition to carboxylation RUBISCO can also fix O2. In C3 plants CO2and O2 compete with each other at the active site of RUBISCO. As a result, one molecule of O2 is fixed by RUBISCO for every three molecules of CO2. When O2is substituted instead of CO2 at the active site of RUBISCO, one molecule of phosphoglycerate and one molecule of phosphoglycolate, a toxic product is formed. Plants can metabolize the phosphoglycolate through the process of photorespiration. Therefore, the glycolate metabolism is associated with photorespiration. Photorespiration results in the loss of at least 25% of assimilated carbon during photosynthesis. In this way plants (C3) loose energy, that results in low productivity. This situation becomes even worse when plant suffers from drought or high temperature stresses. Because in these situations plant closes its stomata to prevent water loss but this results in reduction in CO2diffusion into plant cells for photosynthesis. At this stage photosynthesis is surpassed by photorespiration. Plants having C4 type of photosynthesis have specific modifications to concentrate CO2 near RUBISCO to suppress or eliminate photorespiration, hence, those plants have better water use efficiency. Cyanobacteria also have novel CO2 concentrating mechanisms which may be engineered in C3 type of crop plants to minimize losses due to photorespiration. To overcome these losses,study has been designed to engineer cyanobacterial glycolate catabolism pathway with in chloroplast to bypass the traditional plant glycolate catabolism pathway, which will liberate 2 molecules of CO2 in chloroplast. This will ensure maximum photosynthesis and reduced photorespiration that subsequently will ensure improve productivity. In this study the said pathway will be engineered in potato plants (C3-plant) to improve biomass accumulation.
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