Abstract: An K+ transporter encoding gene（PpeKUP5）was isolated from‘Xiahui 8’peach（Prunus persica）trees. The PpeKUP5 encodes a protein of 625 amino acid residues，which contains 10 transmembrane regions. The PpeKUP5 gene was largely expressed in roots，less in leaves and stems，and very weakly in flowers and fruits. Abscisic acid（ABA）treatment，heavy-metal chromium（Cr）and heavy-metal zinc（Zn），respectively，significantly enhanced the expression level of PpeKUP5 gene throughout whole peach seedlings. Notably，PpeKUP5 gene was most sensitive to Cr treatment. While both K+ excess and heavy-metal copper（Cu）treatment significantly reduced the expression level of PpeKUP5 gene in plant roots. Functional complementation of bacterial mutant showed that PpeKUP5 can utilize external K+（either KCl or K2SO4），especially under neutral pH values. This study favorably reveals that PpeKUP5 is a key K+ transporter mediates roots K+ uptake and accumulation in peach，which may play an important role in response to K+ excess，heavy-metal and ABA stresses.

Key words: peach, potassium transporter, PpeKUP5 gene, gene expression, functional validation