Molecular Plant Breeding 2025, Vol.16, No.1, 63-72 http://genbreedpublisher.com/index.php/mpb 63 Review and Progress Open Access Unveiling Drought Tolerance Mechanisms in Soybean Seed Germination: New Insights from Physiological and Molecular Perspectives Haiying Wang , Lei Wang, Mengdi Yang, Quanrui Song, Yue Guo, Haibo Hong College of Agronomy, Shenyang Agricultural University, Shenyang, 110866, Liaoning, China Corresponding email: wanghy99@syau.edu.cn Molecular Plant Breeding, 2025, Vol.16, No.1 doi: 10.5376/mpb.2025.16.0007 Received: 03 Jan., 2025 Accepted: 15 Feb., 2025 Published: 23 Feb., 2025 Copyright © 2025 Wang et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Wang H.Y., Wang L., Yang M.D., Song Q.R., Guo Y., and Hong H.B., 2025, Unveiling drought tolerance mechanisms in soybean seed germination: new insights from physiological and molecular perspectives, Molecular Plant Breeding, 16(1): 63-72 (doi: 10.5376/mpb.2025.16.0007) Abstract Drought tolerance in soybeans is crucial for ensuring sustainable crop production under increasing climate variability. This study aims to provide a comprehensive overview of the physiological and molecular mechanisms underlying drought tolerance during soybean seed germination, as well as integrative approaches and practical applications in breeding strategies. Physiological mechanisms include osmotic adjustment through proline and soluble sugar accumulation, water uptake and retention mediated by seed coat properties and aquaporins, and antioxidant defense systems involving both enzymatic and non-enzymatic antioxidants. On a molecular level, the study explores gene expression regulation by drought-responsive transcription factors, stress-inducible promoters and genes, signal transduction pathways including ABA-dependent and independent pathways, and genomic and proteomic approaches to identify drought-responsive genes and proteins. Integrative approaches such as systems biology and gene editing tools like CRISPR/Cas9 are discussed for their potential in enhancing drought tolerance. Practical applications focus on breeding strategies, highlighting marker-assisted selection and comparing conventional breeding with biotechnological methods. The study also addresses challenges and opportunities in developing drought-resilient soybean varieties, considering environmental variability, field conditions, and socioeconomic factors. The findings underscore the importance of a multi-faceted approach to improve drought tolerance in soybeans, with implications for global food security. Keywords Drought tolerance; Soybean seed germination; Physiological mechanisms; Molecular mechanisms; Breeding strategies 1 Introduction Soybean (Glycine max L.) is a globally significant crop, providing essential proteins and oils for human consumption and animal feed. However, its productivity is severely threatened by environmental stresses, particularly drought, which is exacerbated by climate change (Buezo et al., 2018; Zhao et al., 2020; Begum et al., 2022). Drought stress during the seed germination stage is especially detrimental, as it can inhibit seedling establishment and reduce overall crop yield (Aleem et al., 2020; Wang et al., 2022). Understanding the mechanisms underlying drought tolerance in soybeans is crucial for developing resilient cultivars that can withstand water-deficit conditions and ensure food security (Aleem et al., 2020; Sun et al., 2022; Xuan et al., 2022). This study aims to provide a comprehensive overview of the physiological and molecular mechanisms that confer drought tolerance during soybean seed germination. By synthesizing findings from recent studies, we seek to highlight key genetic, biochemical, and physiological traits that contribute to drought resilience. The scope of this study includes the identification of drought-tolerance genes, the role of antioxidant metabolism, and the physiological adjustments that enable soybean seedlings to cope with water stress. Through this synthesis, we hope to offer new insights that can inform breeding programs and genetic engineering efforts aimed at enhancing drought tolerance in soybeans. 2 Physiological Mechanisms of Drought Tolerance in Soybean Seed Germination 2.1 Osmotic adjustment Proline accumulation is a critical osmotic adjustment mechanism in soybean seed germination under drought conditions. Proline acts as an osmoprotectant, stabilizing proteins and membranes, and scavenging free radicals. Studies have shown that drought stress leads to a significant increase in proline content in soybean leaves, which
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