Legume Genomics and Genetics 2024, Vol.15, No.5, 257-269 http://cropscipublisher.com/index.php/lgg 261 Figure 2 The GmNFYB17 transgenic soybean lines under drought treatment (Adopted from Sun et al., 2022) Image caption: (A) Morphology of transgenic and non-transgenic plants under drought conditions. Water was withheld for 15 d, and then plants were re-watered for 7 d. G16, G18 and G26 are transgenic lines; CK is soybean DN50; (B, C) The leaf relative water content (RWC) and leaf damage of transgenic lines. G16, G18, G26 and non-transgenic control (CK) during the well-watered, drought and re-watered stage; (D-F) Comparison of physiological and biochemical indicators (MDA, SOD, Proline) between transgenic and non-transgenic plants. *: p-value ≤ 0.05; **: p-value ≤ 0.01 (Adopted from Sun et al., 2022) 4 Molecular Bases of Drought Tolerance 4.1 Gene expression and regulation Transcription factors (TFs) play a crucial role in regulating gene expression in response to drought stress. Several TF families, including WRKY, MYB, DREB, and TGA, have been identified as key players in drought tolerance in soybeans. For instance, GmWRKY54 has been shown to enhance drought tolerance by activating genes in the ABA and Ca2 + signaling pathways, leading to reduced water loss through stomatal closure (Wei et al., 2019). Similarly, GmDREB2, a DREB-type TF, confers drought and high-salt tolerance by binding to dehydration-responsive elements (DREs) and activating downstream stress-responsive genes (Chen et al., 2007). Additionally, GmMYB84, an R2R3-MYB TF, contributes to drought resistance by modulating reactive oxygen species (ROS) levels and enhancing antioxidant enzyme activities (Wang et al., 2017). Drought-inducible genes are crucial for enhancing drought tolerance in soybeans. The expression of these genes is often regulated by specific promoters that respond to drought stress. For example, the GmWRKY54 gene, driven by a drought-induced promoter (RD29a), has been shown to confer drought tolerance in transgenic soybeans (Wei et al., 2019). Another study identified several drought-inducible genes, including those involved in ABA biosynthesis and signaling, such as PYL8, SRK2A, CIPK11, and CPK3, which are directly activated by GmWRKY54. Additionally, the identification of novel DNA elements, such as ABRE and CRT/DRE, in the
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