Key message <p><b>Zinc-finger protein VvSAP8 from grape regulates high-affinity K</b>^<b>+</b><b> transporter VvHAK5 to enhance tolerance to both K</b>^<b>+</b><b> deficiency and salt stresses.</b></p> Abstract <p>Potassium ion (K⁺) deficiency and salt stress are major abiotic factors that restrict the grape industry. Plants respond to K⁺ deficiency and salt stress by regulating K⁺ homeostasis in roots, while the underlying regulatory mechanisms remain unclear. In this study, we identified a high-affinity K⁺ transporter gene (<i>VvHAK5</i>) from the HAK/KUP/KT family in grape, as a root-specifically expressed gene. VvHAK5 was localized to the plasma membrane and exhibited K⁺ transport activity. Gene expression of <i>VvHAK5</i> was induced by both K⁺ deficiency and salt stress. Heterologous overexpression of <i>VvHAK5</i> in tobacco significantly enhanced tolerance to K⁺ deficiency by promoting K⁺ uptake, and simultaneously conferred enhanced tolerance to salt stress by mediating Na⁺/K⁺ homeostasis and improving reactive oxygen species (ROS) scavenging capacity. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase reporter assays confirmed that an A20/AN1-type zinc-finger protein (VvSAP8) could activate the expression of <i>VvHAK5</i> by binding to the TAACTG site on its promoter. Gene expression of <i>VvSAP8</i> was also induced by both K⁺ deficiency and salt stress. Overexpression of <i>VvSAP8 in Arabidopsis</i> could confer tolerance to K⁺ deficiency and salt stress by regulating K⁺ transport, consistent with the function of <i>VvHAK5</i>. Taken together, this study identified a VvSAP8-VvHAK5 regulatory module from grapevines that conferred dual tolerance to K⁺ deficiency and salt stress in plants through coordinated regulation of K⁺ uptake, ion homeostasis, and ROS scavenging.</p>