Two major metabolic factors for an efficient NADP-malic enzyme type C4 photosynthesis |
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| Authors: | Honglong Zhao Yu Wang Ming-Ju Amy Lyu Xin-Guang Zhu |
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| Affiliation: | Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China;The Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Champaign, Illinois 61801, USA |
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| Abstract: | Compared to the large number of studies focused on the factors controlling C3 photosynthesis efficiency, there are relatively fewer studies of the factors controlling photosynthetic efficiency in C4 leaves. Here, we used a dynamic systems model of C4 photosynthesis based on maize (Zea mays) to identify features associated with high photosynthetic efficiency in NADP-malic enzyme (NADP-ME) type C4 photosynthesis. We found that two additional factors related to coordination between C4 shuttle metabolism and C3 metabolism are required for efficient C4 photosynthesis: (1) accumulating a high concentration of phosphoenolpyruvate through maintaining a large PGA concentration in the mesophyll cell chloroplast and (2) maintaining a suitable oxidized status in bundle sheath cell chloroplasts. These identified mechanisms are in line with the current cellular location of enzymes/proteins involved in the starch synthesis, the Calvin–Benson cycle and photosystem II of NADP-ME type C4 photosynthesis. These findings suggested potential strategies for improving C4 photosynthesis and engineering C4 rice.High levels of PGA and PEP in mesophyll cell chloroplasts and a suitable oxidation state in bundle sheath cell chloroplasts are the requirements for efficient C4 photosynthesis. |
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