Journal
SCIENTIFIC REPORTS
Volume 10, Issue 1, Pages -Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41598-020-77894-2
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Funding
- Higher Education Commission of Pakistan [20-4301/RD/HEC/14/619]
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Plants employ photosynthesis to produce sugars for supporting their growth. During photosynthesis, an enzyme Ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco) combines its substrate Ribulose 1,5 bisphosphate (RuBP) with CO2 to produce phosphoglycerate (PGA). Alongside, Rubisco also takes up O-2 and produce 2-phosphoglycolate (2-PG), a toxic compound broken down into PGA through photorespiration. Photorespiration is not only a resource-demanding process but also results in CO2 loss which affects photosynthetic efficiency in C-3 plants. Here, we propose to circumvent photorespiration by adopting the cyanobacterial glycolate decarboxylation pathway into C-3 plants. For that, we have integrated the cyanobacterial glycolate decarboxylation pathway into a kinetic model of C-3 photosynthetic pathway to evaluate its impact on photosynthesis and photorespiration. Our results show that the cyanobacterial glycolate decarboxylation bypass model exhibits a 10% increase in net photosynthetic rate (A) in comparison with C-3 model. Moreover, an increased supply of intercellular CO2 (C-i) from the bypass resulted in a 54.8% increase in PGA while reducing photorespiratory intermediates including glycolate (-49%) and serine (-32%). The bypass model, at default conditions, also elucidated a decline in phosphate-based metabolites including RuBP (-61.3%). The C-3 model at elevated level of inorganic phosphate (Pi), exhibited a significant change in RuBP (+355%) and PGA (-98%) which is attributable to the low availability of C-i. Whereas, at elevated Pi, the bypass model exhibited an increase of 73.1% and 33.9% in PGA and RuBP, respectively. Therefore, we deduce a synergistic effect of elevation in CO2 and Pi pool on photosynthesis. We also evaluated the integrative action of CO2, Pi, and Rubisco carboxylation activity (V-cmax) on A and observed that their simultaneous increase raised A by 26%, in the bypass model. Taken together, the study potentiates engineering of cyanobacterial decarboxylation pathway in C-3 plants to bypass photorespiration thereby increasing the overall efficiency of photosynthesis.
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