The basic leucine zipper (bZIP) transcription factors play crucial roles in plant resistance to environmental challenges, but the biological functions of soybean bZIP members are still unclear. In this study, a drought-related soybean bZIP gene, GmTRAB1, was analyzed. The transcript of GmTRAB1 was upregulated under drought, ABA, and oxidative stresses. Overexpression of GmTRAB1 improved the osmotic stress tolerance of transgenic Arabidopsis and soybean hairy roots associated with increased proline content and activity of antioxidant enzymes and reduced accumulations of malonaldehyde and reactive oxide species. However, RNA interference silencing of GmTRAB1 in the soybean hairy roots improved drought sensitivity. Furthermore, GmTRAB1 increased the sensitivity of transgenic plants to ABA and participated in modulating ABA-regulated stomatal closure upon drought stress. In addition, GmTRAB1 stimulated the transcript accumulation of drought-, ABA-, and antioxidant-related genes to respond to drought. Collectively, this research will contribute to understanding the molecular mechanisms of bZIP transcription factors in soybean’s resistance to drought.

Salt stress severely limits soybean production worldwide. Calcineurin B-like protein-interacting protein kinases (CIPKs) play a pivotal role in a plant’s adaption to salt stress. However, their biological roles in soybean adaption to salt stress remain poorly understood. Here, the GmCIPK2 expression was increased by NaCl and hydrogen peroxide (H₂O₂). GmCIPK2-overexpression Arabidopsis and soybean hairy roots displayed improved salt tolerance, whereas the RNA interference of hairy roots exhibited enhanced salt sensitivity. Further analyses demonstrated that, upon salt stress, GmCIPK2 enhanced the proline content and antioxidant enzyme activity and decreased the H₂O₂ content, malondialdehyde (MDA) content, and Na⁺/K⁺ ratios in soybean. Moreover, GmCIPK2 promoted the expression of salt- and antioxidant-related genes in response to salt stress. Moreover, the GmCIPK2-interacting sensor, GmCBL4, increased the salt tolerance of soybean hairy roots. Overall, these results suggest that GmCIPK2 functions positively in soybean adaption to salt stress.

Salt stress seriously restricts the yield and quality of soybean. Calcineurin B subunit-interacting protein kinases (CIPKs) play a vital role in response to environmental stresses in plant. However, few study is known about the biological function of soybean CIPKs. In this study, GmCIPK10 was cloned from soybean genome. Bioinformatics analysis exhibited that GmCIPK10 encoded an intron-poor type CIPKs with a serine (Ser)/threonine (Thr) protein kinase domain and a NAF/FISL motif. The relative expression pattern levels showed that the transcript level of GmCIPK10 was increased under NaCl, MV, and H2O2 treatments. Overexpression of GmCIPK10 in Arabidopsis and soybean hairy roots improved salt tolerance of transgenic plants. Further physiological indicator assays demonstrated that GmCIPK10 overexpression could decrease the accumulation of MDA and H2O2, enhance the activity of antioxidant enzymes, and reduce sodium (Na+)/potassium (K+) in transgenic plants under salt stress. In addition, qRT-PCR illustrated that GmCIPK10 promoted the relative expression level of antioxidant- and salt tolerance-related gene in salt stress. The yeast two-hybrid, pull-down, and bimolecular fluorescence complementation experiments confirmed that GmCIPK10 interacts with the Ca2+ sensor GmCBL4. These results provide a reference for investigating the role of the CBL-CIPK signaling pathway in response to salt stress in soybean.

Drought and salinity are major abiotic stresses that severely constrain plant growth and agricultural productivity. Histidine kinases (HKs), as key components of the plant two-component system (TCS), play crucial roles in environmental signal perception and adaptive responses. In this study, we functionally characterized a sweet potato (Ipomoea batatas L.) HK gene, IbHK1a, and investigated its role in drought and salt stress tolerance. Expression analysis revealed that IbHK1a is predominantly expressed in root tissues, particularly in storage and fibrous roots, indicating its potential involvement in stress sensing and adaptation. Subcellular localization demonstrated that the IbHK1a protein is localized to the plasma membrane, suggesting a role in external signal perception. To elucidate its biological function, IbHK1a was heterologously overexpressed in Arabidopsis thaliana. Transgenic plants exhibited significantly enhanced tolerance to drought and salt stress, as evidenced by higher seed germination rates, improved primary root growth, reduced leaf wilting, and increased survival rates compared with wild-type (WT) plants. Physiological analyses showed that IbHK1a overexpression led to increased activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), accompanied by reduced accumulation of reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Consistently, leaf histochemical staining confirmed lower ROS accumulation in transgenic plants under stress conditions. In sweet potato, overexpression of IbHK1a in transgenic hairy roots enhanced tolerance to drought and salinity, whereas RNA interference lines displayed increased sensitivity, further confirming its positive regulatory role. Additionally, protein interaction analysis indicated that IbHK1a interacts with Arabidopsis histidine phosphotransferase proteins (AHPs), suggesting its involvement in conserved TCS-mediated phosphorelay signaling pathways. Functional complementation analysis demonstrated that IbHK1a partially rescues the stress-sensitive phenotype of the AHK1 mutant, indicating functional conservation with Arabidopsis AHK1. Collectively, these findings demonstrate that IbHK1a positively regulates drought and salt stress tolerance by enhancing antioxidant defense and ROS homeostasis. Its interaction with AHPs and partial complementation of the ahk1 mutant further support its involvement in the conserved TCS phosphorelay pathway. These results establish IbHK1a as an important component of abiotic stress responses and a potential genetic target for improving drought and salinity tolerance in sweet potato.