H v ZIP 7 mediates zinc accumulation in barley ( H ordeum vulgare ) at moderately high zinc supply

Summary High expression of zinc ( Z n)‐regulated, iron‐regulated transporter‐like protein ( ZIP ) genes increases root Z n uptake in dicots, leading to high accumulation of Z n in shoots. However, none of the ZIP genes tested previously in monocots could enhance shoot Z n accumulation. In this report, barley ( H ordeum vulgare ) H v ZIP 7 was investigated for its functions in Z n transport. The functions of H v ZIP 7 in planta were studied using in situ hybridization and transient analysis of subcellular localization with a green fluorescent protein ( GFP ) reporter. Transgenic barley lines overexpressing H v ZIP 7 were also generated to further understand the functions of H v ZIP 7 in metal transport. H v ZIP 7 is strongly induced by Z n deficiency, primarily in vascular tissues of roots and leaves, and its protein was localized in the plasma membrane. These properties are similar to its closely related homologs in dicots. Overexpression of H v ZIP 7 in barley plants increased Z n uptake when moderately high concentrations of Z n were supplied. Significantly, there was a specific enhancement of shoot Z n accumulation, with no measurable increase in iron ( F e), manganese ( M n), copper ( C u) or cadmium ( C d). H v ZIP 7 displays characteristics of low‐affinity Z n transport. The unique function of H v ZIP 7 provides new insights into the role of ZIP genes in Z n homeostasis in monocots, and offers opportunities to develop Z n biofortification strategies in cereals.