Journal of Energy Bioscience 2025, Vol.16, No.5, 238-247 http://bioscipublisher.com/index.php/jeb 239 The purpose of this research is to sort out the molecular regulatory mechanisms of photosynthesis in C4 plants, introduce the latest progress of genetic engineering in increasing the yield of biofuels, analyze the existing problems at present, and look forward to the future development direction. It is hoped that by integrating multiple factors such as genetics, molecules and the environment, references can be provided for the design and cultivation of efficient bioenergy crops that adapt to future climate change. 2 C4 Photosynthesis and Its Advantages for Biofuel Crops 2.1 Overview of the C4 photosynthetic mechanism C4 Photosynthesis is a special form of carbon fixation, mainly existing in high-yield crops such as corn, sorghum and sugarcane. Unlike C3 plants, C4 plants complete the CO2 concentration process in two types of cells, namely mesophyll cells and vascular bundle sheath cells. First, phosphoenolpyruvate carboxylase (PEPC) fixes CO2 in mesophyll cells into four-carbon compounds, such as oxaloacetic acid. Then these compounds are transported to the vascular bundle sheath cells, where CO2 is released and handed over to RuBisCO to enter the Calvin cycle. In this way, photorespiration is greatly reduced and the efficiency of carbon fixation is also higher (Ermakova et al., 2020; Cui, 2021; Sahoo et al., 2024; Prasanna et al., 2025) (Figure 1). Figure 1 Diagram of the leaf anatomy of typical C3 (A) and C4 (B) plants. 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) 2.2 Key advantages for biofuel: higher biomass yield, water use efficiency, nitrogen use efficiency C4 plants have many advantages in biofuel production. First of all, the output is high. Like corn, sugarcane and sorghum, they have high photosynthetic efficiency and good energy conversion rate, so they can produce more biomass per unit area than C3 plants (Byrt et al., 2011; Mullet, 2017). Theoretically, the photosynthetic energy conversion efficiency of C4 plants can reach 6%, and their actual performance in the field is also better than that of C3 plants (Keller et al., 2021; Wang et al., 2021). The utilization efficiency of water is also very high. Because
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