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<i>ZIP4</i> (zinc transporter 4) plays important roles in transporting Cu²⁺ ions in plants, which may contribute to the maintenance of plant metal homeostasis in growth, plant development and normal physiological metabolism. However, <i>ZIP4</i> transporters have not been described in mulberry and the exact function of <i>ZIP4</i> transporters in regulating the homeostasis of Cu in mulberry remains unclear. In this study, a new <i>ZIP4</i> gene (<i>MaZIP4</i>) was isolated and cloned from <i>Morus atropurpurea</i> R. Phylogenetic analysis of amino sequences suggested that the amino-acid sequence of the <i>MaZIP4</i> protein shows high homology with other <i>ZIP4</i> proteins of <i>Morus notabilis</i>, <i>Trema orientale</i>, <i>Ziziphus jujube</i> and <i>Cannabis sativa</i>. In addition, a <i>MaZIP4</i> silenced line was successfully constructed using virus-induced gene silencing (VIGS). The analysis of <i>MaZIP4</i> expression by quantitative real-time PCR in mulberry showed that the level of <i>MaZIP4</i> expression increased with increasing Cu concentration until the Cu concentration reached 800 ppm. Relative to the blank (WT) and the negative controls, malondialdehyde (MDA) levels increased significantly and rose with increasing Cu concentration in the <i>MaZIP4</i> silenced line, whereas the soluble protein and proline content, superoxide dismutase (SOD) and peroxidase (POD) activities of these transgenic plants were lower. These results indicated that <i>MaZIP4</i> may play an important role in the resistance of mulberry to Cu stress.