Soybean (Glycine max L.) is an essential food and economic crop in China, yet its growth and yield are severely constrained by saline–alkali stress. A saline–alkali soil exacerbates root absorption barriers, leading to 30–50% yield losses. Understanding the mechanisms underlying alkali tolerance is therefore crucial for developing stress-resilient soybean varieties and improving the productivity of saline–alkali land. In our previous study, we evaluated 99 soybean germplasms from Northeast China and obtained the alkali-tolerant varieties HN48 and HN69, along with the alkali-sensitive varieties HNWD4 and HN83. In this study, fifteen-day-old soybean seedlings were subjected to (30 mM NaHCO₃) alkali stress for 72 h, and whole plants were sampled to assess their morphology and physiology, while leaf tissues were harvested for biochemical analysis. For transcriptomic analysis, soybean seedlings were exposed to alkali stress (50 mM NaHCO₃, pH 9.0) for 6 h, and leaf and root tissues were harvested for RNA sequencing. The results showed that alkali-tolerant varieties mitigated these effects by suppressing excessive ROS generation by 55–63%, decreasing malondialdehyde (MDA) accumulation by 37–39%, and increasing photosynthetic efficiency by 18.3%, as well as accumulating more osmoprotectants and activating antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) under alkaline stress. Transcriptome analysis showed that the alkali-tolerant variety HN69 exhibited cultivar-specific enrichment of metabolism cytochrome P450, estrogen signaling, and GnRH signaling pathways under alkali stress. These results collectively indicate that alkali-tolerant soybean varieties adapt to alkali stress through coordinated multi-pathway responses, with differential pathway enrichment potentially underlying the variation in alkali tolerance between cultivars. Overall, this study elucidates the physiological and molecular mechanisms of alkali tolerance in soybean, providing a theoretical foundation for breeding stress-tolerant germplasms.

Heavy metal-associated isoprenylated plant protein (HIPP) family genes are known to be involved in plant development and stress responses. Even though the HIPPs have been identified and characterized in some plants, the roles of these genes in plant abiotic stress tolerance remain unclear in G. soja (Glycine soja), especially in response to alkaline stress. In the present study, a total of 79 potential HIPP family genes were obtained in G. soja using the Hidden Markov Model. Bioinformatics analysis was used to explore their physicochemical properties, gene structure, phylogenetic relationships, cis-acting elements, chromosomal location and collinearity. Expression profiling showed that 18 HIPP family genes were displayed significantly different transcript levels under alkaline stress, among which GsHIPP79 was selected for functional characterization. The results showed that GsHIPP79 exhibited enhanced alkaline stress tolerance in transgenic Arabidopsis plants, as evidenced by it exhibiting higher chlorophyll contents, strengthening the antioxidant defense system, and regulating the expression of stress-responsive marker genes. Moreover, overexpression of GsHIPP79 in transgenic soybean hairy roots conferred enhanced alkaline stress tolerance. In conclusion, this study provided valuable information on HIPP family genes in G. soja and identified the positive roles of GsHIPP79 in response to alkaline stress tolerance.

Zinc/iron-regulated transporter proteins (ZIPs) are involved in the transport of zinc and iron, maintenance of ion homeostasis, and regulation of plant responses to abiotic stresses. Although previous studies have identified members of the ZIP gene family and screened for alkaline-responsive ZIP genes in wild soybean (Glycine soja), the functional implications of these genes under alkaline stress conditions remain to be fully elucidated. The present study aimed to identify the GsZIP7 gene and investigate its regulatory role in Arabidopsis and wild soybean under alkaline stress. The results showed that GsZIP7 was highly expressed in roots and young stems. GsZIP7 exhibited differential expression in response to alkaline stress, zinc deficiency, or iron deficiency in wild soybean. In addition, heterologous expression of GsZIP7 in yeast mutants increased tolerance to iron- and zinc-deficient conditions. Overexpression of GsZIP7 in Arabidopsis resulted in reduced root growth, decreased fresh weight, and a weakened antioxidant defense system. Furthermore, GsZIP7-overexpressing soybean hairy roots showed increased sensitivity to alkaline stress, whereas GsZIP7-RNAi lines exhibited enhanced tolerance. Together, these findings indicate that GsZIP7 negatively regulates alkaline tolerance in plants.