Legume Genomics and Genetics 2026, Vol.17, No.1, 32-48 http://cropscipublisher.com/index.php/lgg 32 Research Report Open Access Transcriptomic Insights into Drought Stress Response in Soybean (Glycine max L.) Weiguo Lu , Lijun Qiu Modern Agricultural Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China Corresponding email: lijun.qiu@cuixi.org Legume Genomics and Genetics, 2026 Vol.17, No.1 doi: 10.5376/lgg.2026.17.0003 Received: 11 Feb., 2026 Accepted: 14 Feb., 2026 Published: 24 Mar., 2026 Copyright © 2026 Lu and Qiu, 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: Lu W.G., and Qiu L.J., 2026, Transcriptomic insights into drought stress response in soybean (Glycine max L.), Legume Genomics and Genetics, 17(1): 32-48 (doi: 10.5376/lgg.2026.17.0003) Abstract Drought stress is a major abiotic stress factor that limits soybean growth and development, yield formation, and quality stability; its impact spans multiple critical stages, including germination, vegetative growth, reproductive development, and grain filling. With the rapid advancement of high-throughput sequencing technologies, transcriptomics has emerged as a crucial tool for deciphering the molecular mechanisms underlying drought tolerance in soybeans. Focusing on the theme of "transcriptomic analysis of soybean responses to drought stress," this review begins by outlining the physiological basis of soybean drought responses. It then systematically summarizes the workflow, data analysis methods, and strategies for identifying differentially expressed genes using RNA-Seq technology in drought tolerance research. Particular emphasis is placed on summarizing the regulatory roles of transcription factor families-such as WRKY, NAC, bZIP, and DREB-in drought signal transduction, osmotic adjustment, antioxidant defense, and hormonal responses. Furthermore, by integrating studies on non-coding RNAs, co-expression networks, and candidate gene functional validation, this review explores the structural characteristics of multi-layered gene regulatory networks involved in soybean drought responses. The review also utilizes comparative transcriptomic analyses of soybean accessions with varying degrees of drought tolerance to analyze the expression patterns of key drought-tolerance genes and assess their potential for application in molecular breeding. Overall, transcriptomics has not only deepened our understanding of the mechanisms underlying soybean responses to drought stress but has also provided a theoretical foundation for the discovery of drought-tolerance genes, the development of molecular markers, and precision breeding. Future research should prioritize the integration of multi-omics data with field-based phenotyping to enhance the depth of mechanistic analysis and improve the efficiency of breeding applications. Keywords Soybean; Drought stress; Transcriptomics; Differentially expressed genes; Drought-tolerance breeding 1 Introduction Soybean (Glycine max L.) is a major source of plant protein and oil, underpinning global food, feed, and industrial markets. However, its productivity is highly vulnerable to water deficits, especially in rainfed production systems and regions where climate change is intensifying the frequency and duration of drought events (Haghpanah et al., 2024). Drought stress disrupts plant water relations, reduces photosynthesis, alters carbon allocation, and ultimately depresses biomass accumulation and yield (Razi and Muneer, 2021). Controlled and field studies in soybean have shown that reductions in soil moisture below about 75% of field capacity lead to decreases in leaf area index, growth rate, and seed yield, with particularly strong sensitivity during reproductive stages (Wang et al., 2025). Yield penalties of 50%-80% have been reported when severe drought occurs at flowering, pod setting, or seed filling, often associated with reductions in pod number, seed number, and 100-seed weight (Wei et al., 2018; Aziez et al., 2022). In addition to quantitative yield losses, drought alters seed quality by modifying protein and oil content, which further compromises the economic value of the crop (Poudel et al., 2023). Drought responses in soybean are stage-dependent and genotype-dependent, adding complexity to breeding and management. Experiments across multiple environments indicate that the flowering and grain-filling stages are particularly vulnerable, with grain-filling drought often causing the largest yield reductions and quality shifts (Demirtas et al., 2010). Even within modern commercial cultivars adapted to temperate regions such as Ontario, Canada, substantial genetic variation exists for drought tolerance indices based on yield under stress relative to well-watered conditions, reflecting differences in water use, biomass maintenance, and pod retention (Gebre et al.,
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