Molecular Plant Breeding 2025, Vol.16, No.1, 63-72 http://genbreedpublisher.com/index.php/mpb 64 helps in maintaining cell turgor and minimizing damage caused by dehydration (Fatema et al., 2023; Begum et al., 2022; Wang et al., 2022). Additionally, proline accumulation has been observed to correlate with drought tolerance in various soybean cultivars, indicating its essential role in osmotic adjustment (Figure1) (Du et al., 2020). Figure 1 A model of the nitrogen regulation in soybean leaf in response to drought stress (Adopted from Du et al., 2020) Image caption: Here, drought stress triggers a nitrogen-mediated tandem reaction in response to drought stress. Drought stress might change the expression of key regulatory metabolic genes and the activities of nitrogen metabolism enzymes, which regulate nitrogen distribution and utilization to adapt to environmental stress. NR, nitrate reductase; NiR, nitrite reductase; GS, glutamine synthetase; GOGAT, glutamate synthetase; Glu, glutamate; Gln, glutamine; 2-OXG, 2-oxoglutarate. Increased items under drought stress are marked with upward red arrows and decreased items are marked with downward green arrows (Adopted from Du et al., 2020) Soluble sugars, such as sucrose and glucose, play a vital role in osmotic adjustment by maintaining osmotic balance and protecting cellular structures during drought stress. Study indicates that drought conditions lead to an increase in soluble sugar content in soybean plants, which contributes to osmotic adjustment and stress tolerance (Gurrieri et al., 2020; Moloi and Merwe, 2021; Wang et al., 2022). The accumulation of soluble sugars has been shown to be more significant than proline in some cases, highlighting their predominant role in counteracting osmotic stress (Gurrieri et al., 2020; Ozturk et al., 2020). 2.2 Water uptake and retention The seed coat properties of soybean seeds influence water uptake and retention, which are crucial for germination under drought conditions. A robust seed coat can reduce water loss and enhance water retention, thereby supporting seed germination and seedling establishment during water-deficit conditions. Studies have demonstrated that drought-tolerant soybean varieties possess seed coats with better water retention capabilities, contributing to their overall drought resilience (Song et al., 2022; Fatema et al., 2023). Aquaporins are water channel proteins that facilitate water transport across cell membranes, playing a significant role in water uptake and retention during drought stress. The expression of aquaporins is often upregulated in response to drought, enhancing the plant’s ability to maintain water balance and support seed germination. study has shown that aquaporins are crucial for maintaining cellular water homeostasis and improving drought tolerance in soybean (Sheteiwy et al., 2021; Fatema et al., 2023; Wang et al., 2024).
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