Journal of Energy Bioscience 2025, Vol.16, No.4, 205-215 http://bioscipublisher.com/index.php/jeb 207 Improving photosynthetic efficiency and yield: The C4 pathway can reduce photorespiration loss and increase CO2 utilization, thereby significantly enhancing photosynthetic rate and yield (Rangan et al., 2016; Bachir et al., 2017; Daoura et al., 2018; Prasanna et al., 2025). Enhancing water and nitrogen utilization efficiency: C4 crops are more efficient in water and nitrogen utilization, which helps wheat maintain higher yields when resources are insufficient or the environment is harsh (Matsuoka et al., 2003; Jia et al., 2015; Prasanna et al., 2025). Adapting to climate change: C4 characteristics can help wheat adapt to potentially hotter and drier climates in the future and ensure food security (Jia et al., 2015; Rangan et al., 2016). Enhancing stress resistance: Increasing the expression and activity of C4 enzyme in wheat, especially in panicles and different organs, can enhance drought resistance and delay senescence (Jia et al., 2015; Bachir et al., 2017; Zhang et al., 2019). 3.2 Lessons from past C4 engineering attempts in rice Rice is the object with the most in-depth C4 engineering research among C3 crops, and these studies provide important references for wheat: The effect of introducing a single enzyme is limited: Although adding only one C4 enzyme (such as PEPC) can affect carbon metabolism, it has little effect on improving photosynthetic efficiency and requires the combination of multiple enzymes (Matsuoka et al., 2003; Miyao, 2003; Schuler et al., 2016; Prasanna et al., 2025). Anatomical structure limitations: The C4 pathway requires spatial separation between mesophyll cells and vascular bundle sheath cells (Kranz structure), which is lacking in C3 crops and is a major obstacle to engineering (Matsuoka et al., 2003; Schuler et al., 2016; Cui, 2021) (Figure 1). Figure 1 Diagram of the leaf anatomy of typical C3 (A) and C4 (B) plants (Adopted from Cui, 2021) Note: In C4 plants, there are two mesophyll cells between neighboring vascular bundles, whereas in C3 plants, there are more than two. Also, the bundle sheath cells in C4 plants are much larger and contain more chloroplasts, as indicated by color intensity (Adopted from Cui, 2021) Complex gene regulation: The high-level and cell-specific expression of the C4 gene requires precise control, which involves a complex gene regulatory network (Schuler et al., 2016; Cui, 2021; Chen et al., 2023).
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