Physiological functions of the transcription factor GmZAT10-1 gene involved in the salt stress adaptation in soybean

C2H2-type zinc finger proteins (ZFPs) play important roles in the gene transcriptional regulation in the response of plants to multiple stressful environments. In this work, the responses of the soybean ZFP family member GmZAT10–1 gene and its promoter to salt stress, and the changes in the seedling growth phenotype, as well as the related physiological parameters in overexpressing (OE)– or CRISPR/Cas9 (KO)–GmZAT10–1 hairy-root composite soybean seedlings and transgenic Arabidopsis thaliana under salt stress were investigated. The results showed that both GmZAT10–1 and its promoter exhibited enhanced induction to salt stress, and the GmZAT10–1 protein displayed the transcriptional activation activity and was located in the cell nucleus. Transient expression of GmZAT10–1 in tobacco leaves and yeast one-hybrid assay (Y1H) revealed that GmZAT10–1 can bind to the promoter of GmCLC-c1 to enhance the expression of the target genes. Compared with the empty vector–transformed (Ev) hairy-root composite soybean plants, the salt-stressed OE-GmZAT10–1 and KO-GmZAT10–1 plants presented mitigated salt injury, greater plant height, fresh weight per plant, leaf relative water content (RWC) and chlorophyll content, and lower relative electrolytic leakage (REL) and malondialdehyde (MDA) content in the roots and leaves, among which the accumulation of Cl^– and NO₃^– increased significantly in the roots of OE-GmZAT10–1, which obviously reduced the transport and accumulation of Cl^– to the stems and leaves, and thus resulting in a marked decrease in Cl^–/NO₃^– ratio in the roots, stems and leaves. By introducing the GmZAT10–1 gene into A. thaliana wild-type (WT) and atzat10 mutant, the seed germination rates and root lengths of WT-GmZAT10–1 and atzat10-GmZAT10–1 under salt stress were obviously restored, and the leaf chlorophyll content and RWC were significantly increased, whereas the REL values and MDA contents were significantly decreased. Additionally, significant accumulation of Cl^– and Na⁺ was observed in the roots, which resulted in a significant decrease in Cl^–/NO₃^–and Na⁺/K⁺ ratios in the shoots. Taken together, these findings indicate that the transcription factor GmZAT10–1 may confer salt tolerance in soybeans by upregulating the expression of the GmCLC-c1 gene through binding to its promoter, regulating the uptake of Cl^– by the roots and reducing its translocation to the above-ground parts, including the stems and leaves of the plants, thereby maintaining a relatively low Cl^–/NO₃^– ratio.