Journal of Energy Bioscience 2024, Vol.15, No.6, 378-387 http://bioscipublisher.com/index.php/jeb 380 expression of GmIFS2 and GmF3H1 (flavanone 3 β-hydroxylase 1), GmZFP7 can promote the accumulation of flavonoids and direct the metabolic flow of flavonoids to the flavonoid biosynthesis pathway (Feng et al., 2022) (Figure 1). In recent years, several new MYB transcription factors (such as GmMYB102, GmMYB280 and GmMYB502) have been identified as potential regulatory factors. Overexpression of these transcription factors can significantly enhance the synthesis of isoflavones in transgenic soybean hairy roots, further demonstrating the importance of the MYB transcription factor family in regulating isoflavone biosynthesis (Sarkar et al., 2019). Figure 1 GmZFP7-mediated regulatory model for soybean isoflavone biosynthesis (Adopted from Feng et al., 2022) Image caption: Black arrows indicate the relationship between isoflavone-related enzymes. The green arrow indicates a promoting effect. The red ‘T’ line and red arrow indicate an inhibitory effect. The dashed arrow indicates that the results are yet to be confirmed experimentally. The double arrows indicate competition. 4CL, 4-coumarate-CoA ligase; C4H, cinnamic acid 4-hydroxylase; CHI, chalcone isomerase; CHR, chalcone reductase; CHS, chalcone synthase; F3′5′H, flavonoid 3'5'-hydroxylase; F3′H, flavonoid 3′-hydroxylase; F3H1, flavanone 3-hydroxylase 1; FLS, flavonol synthase; IFS2, isoflavone synthase 2; PAL, phenylalanine ammonia-lyase (Adopted from Feng et al., 2022) 3.2 Co-regulation with other secondary metabolic pathways The biosynthesis of soybean isoflavones is closely related to other secondary metabolic pathways, especially the phenylpropanoid pathway. Phenylpropanoid pathway genes are activated by transcription factors such as maize C1 and R. Yu et al. (2003) found that these transcription factors can increase isoflavone levels by regulating the flux of the pathway. Feng et al. found in 2022 that GmZFP7 can exert its effects by affecting the phenylpropanoid pathway, increase isoflavone content, and regulate stress resistance mechanisms (Figure 1). In addition, the diurnal regulation of isoflavone and soybean saponin biosynthesis genes shows a coordinated expression pattern
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