A practical guide to using a kinetic model for improving the efficiency of C4 photosynthetic metabolism

Abstract C4 photosynthesis represents a precise integration of biochemical and morphological adaptations that enhance CO2 concentration around Rubisco, reducing energy losses from photorespiration and increasing efficiencies in light, nitrogen, and water use compared with C3 photosynthesis. This advancement has the potential to significantly boost crop yields, meeting the rising demands for food and energy. To conduct a quantitative analysis of the anatomical, cellular, and biochemical components critical to C4 photosynthesis, we developed a comprehensive systems model of NADP-malic enzyme subtype C4 photosynthesis. This model includes the C4 shuttle, Calvin–Benson cycle, starch and sucrose synthesis, CO2 leakage, photorespiration, and metabolite transport between the bundle sheath cells and mesophyll cells. The model effectively simulates CO2 uptake rates and metabolite dynamics under varying conditions, identifying potential bottlenecks in photosynthesis. Enhancements to the original model incorporated aspartate and alanine as transport acids and the phosphoenolpyruvate carboxykinase pathway, which allows the users to explore the impact of diverse decarboxylation mechanisms. This model serves as a valuable tool for dissecting the systems properties and biochemical foundations of C4 photosynthesis. Once well parameterized, it promises to be an instrumental resource in guiding future breeding and genetic engineering efforts aimed at optimizing C4 crop species. We have provided detailed instructions to facilitate its use.