AcGSTU1 enhances salt tolerance of polyploid Actinidia chinensis by dosage effect and is regulated by transcription factor AcERF3

• Polyploidization enhances ROS-scavenging ability to resist salt stress in kiwifruit. • AcGSTU1 improves salt stress tolerance by enhancing ROS scavenging. • Doseage effect of AcGSTU1 contribute to salt tolerance in polyploid kiwifruit. • AcERF3 activates the expression of AcGSTU1 and positively regulates salt tolerance. Polyploidy is a dominant feature of plant diversity and plays an important role in the speciation and evolution of plant species. Compared to diploids, polyploids exhibit greater adaptability to a broader spectrum of environmental conditions. However, the physiological and molecular mechanisms of adaptation remain largely unexplored. In this study, transcriptome, genetic and biochemical techniques were used to investigate the molecular mechanisms of salt stress resistance between diploid and polyploidy (tetraploid, and hexaploid) Actinidia chinensis . The analysis of differently expressed genes (DEGs) reveals significant differences in gene expression among Actinidia chinensis leaves of different ploidy, displaying distinct dose-response characteristics. Further analysis obtained a gene with significant positive dosage effect, namely AcGSTU1 . Overexpressed the AcGSTU1 in both Arabidopsis thaliana and Actinidia chinensis revealed that AcGSTU1 was responsible for polyploidy Actinidia chinensis tolerance to salt stress. In addition, AcGSTU1 may enhance the salt stress tolerance of Actinidia chinensis by increasing ROS scavenging. Besides, we found that transcription factor AcERF3 positively regulates salt stress tolerance by directly binding on the promoter of AcGSTU1 to activate its expression. In conclusion, our work provides insights into the adaptation mechanism of polyploid Actinidia chinensis to salt stress.