Journal of Energy Bioscience 2024, Vol.15, No.6, 378-387 http://bioscipublisher.com/index.php/jeb 382 anthocyanin synthesis pathway). In their study, they effectively reduced the transfer of precursor compounds to anthocyanin metabolites, making more substrates available for the biosynthesis of isoflavones, thereby significantly improving their accumulation level. 5 Impact of Environmental Factors on Isoflavone Levels 5.1 Light and temperature effects on isoflavone accumulation The accumulation level of isoflavones in soybean seeds is largely influenced by environmental factors, among which the effects of light intensity and temperature conditions are particularly significant. Caldwell et al. (2005) found that increasing temperature can inhibit the synthesis of isoflavones during seed development. When the seed development temperature increased from 18 ° C to 23 ° C, the total content of isoflavones decreased by 65%, and further increased to 28 ° C, the decrease in content was as high as 90%. Chennupati et al. (2012) found that during the late stage of soybean reproduction (R5-R8 stage), when subjected to high temperature stress, the concentration of seed isoflavones decreased by 46-86%. These data indicate that high temperatures not only inhibit the activity of key biosynthetic enzymes, but may also affect transcriptional regulatory networks, leading to a significant decrease in isoflavone metabolic flux. At the same time, lighting conditions are also one of the important factors affecting the accumulation of isoflavones. Barion et al. (2021) found that soybean plants exposed to morning light (east facing) exhibited higher total cotyledon isoflavone concentration (TCIC) compared to those exposed to afternoon light (west facing) (Figure 2). This phenomenon may be related to the role of light signals in regulating gene expression related to the phenylpropanoid pathway. Morning light may be more conducive to activating the expression of isoflavone synthesis related enzymes, thereby increasing metabolic flux. Figure 2 Sketch of the experimental trial, front section: west-lighted plants (a; “west”treatment) and east-lighted plants (b; “east” treatment) (Adopted from Barion et al., 2021) 5.2 Influence of soil nutrients and water availability Soil moisture has an important influence on the synthesis of isoflavones in soybean seeds. In their 2005 study, Lozovaya et al. found that high soil moisture content is conducive to the accumulation of isoflavones, while water stress significantly inhibits their synthesis. Gutierrez Gonzalez et al. (2010) found that sufficient water can help isoflavones maintain a high metabolic activity and promote the expression of enzymes related to their biosynthesis. The mineral nutrient content of the soil has little effect on the synthesis of isoflavones. The field experiment of Kurosaki et al. (2023) showed that conventional fertilization measures such as potassium (K), nitrogen (N), phosphorus (P), and molybdenum (Mo) had no significant effect on the isoflavone content of soybean seeds. These research results can show that in the process of isoflavone accumulation, water has a more important regulatory role than mineral nutrition. Therefore, in the cultivation and management of soybeans, optimizing water management will be more effective than a simple fertilization strategy. 5.3 Stress-induced isoflavone production in soybean The accumulation of soy isoflavones is affected by various environmental stresses, including drought, water stress, and mechanical damage. Caldwell et al. found in 2005 that drought stress can significantly affect isoflavone
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