Integrated CUT&Tag-seq and RNA-seq analysis reveals the transcriptional regulatory network of Gshdz4 under alkaline and heavy metal stress

Soil alkalinity and heavy metal toxicity are major abiotic stresses that severely limit plant growth and crop productivity. Wild soybean (Glycine soja) exhibits strong alkaline tolerance, making it a valuable genetic resource for improving cultivated soybean. Previous studies identified Gshdz4 and GsNAC019 as key alkaline-tolerant transcription factors, and GsEXPA8 as an alkaline-tolerant expansin protein. This study establishes a hierarchical "nucleus-nucleus-membrane" regulatory model in wild soybean, wherein the nuclear master transcription factor Gshdz4 transcriptionally upregulates GsNAC019, which in turn activates the expression of the plasma membrane-localized expansin GsEXPA8, collectively enhancing alkaline tolerance. We further investigated the role of Gshdz4 in conferring resistance to combined sodium bicarbonate and cadmium chloride stress in soybean. Through integrated RNA-seq and CUT&Tag-seq analyses, we identified Gshdz4 as a direct binder and regulator of diverse stress-responsive genes-including GmDEAH5, GmHSP22.3, GmACR4, and GmATG1c. Under alkaline stress, Gshdz4 modulates GmSLX8, GmSF3, and GmPP4; under cadmium stress, it regulates GmGMFL01 and GmUNC, establishing a broad-spectrum defense mechanism. Additional targets encompass splicing factors, heat shock proteins, ABA signaling components, and ethylene-responsive factors. GO and KEGG enrichment analyses confirmed that Gshdz4 participates in multiple hormonal pathways (ABA, IAA, ET, JA) and stress response signaling. Our findings revealed Gshdz4 as a master transcriptional regulator under multiple stresses and provide a theoretical foundation for molecular breeding strategies to enhance soybean resilience.