HvZIP7 mediates zinc accumulation in barley (Hordeum vulgare) at moderately high zinc supply

Abstract

SummaryHigh expression of zinc (Zn)-regulated, iron-regulated transporter-like protein (ZIP) genes increases root Zn uptake in dicots, leading to high accumulation of Zn in shoots. However, none of the ZIP genes tested previously in monocots could enhance shoot Zn accumulation. In this report, barley (Hordeum vulgare) HvZIP7 was investigated for its functions in Zn transport.The functions of HvZIP7 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 HvZIP7 were also generated to further understand the functions of HvZIP7 in metal transport.HvZIP7 is strongly induced by Zn 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 HvZIP7 in barley plants increased Zn uptake when moderately high concentrations of Zn were supplied. Significantly, there was a specific enhancement of shoot Zn accumulation, with no measurable increase in iron (Fe), manganese (Mn), copper (Cu) or cadmium (Cd). HvZIP7 displays characteristics of low-affinity Zn transport.The unique function of HvZIP7 provides new insights into the role of ZIP genes in Zn homeostasis in monocots, and offers opportunities to develop Zn biofortification strategies in cereals.

Many rivers to cross: the journey of zinc from soil to seed

“…Other members of the ZIP ( Z RT- I RT-like P rotein) family of metal transporters, to which IRT1 and IRT2 belong, have been proposed to import zinc into roots (Grotz et al, 1998; Lin et al, 2009) but this assumption has recently been questioned as functional studies with plants mutated in the major root ZIP genes, At ZIP1, and At ZIP2 , point to a role of these transporters in root to shoot transport (Milner et al, 2013). The barley transporter HvZIP7 is important for zinc uptake but is localized in root vascular tissue suggesting a similar role in promoting root to shoot transport (Tiong et al, 2013). In rice, OsZIP1 and OsZIP3 have been proposed to be involved in root zinc uptake whereas OsZIP 4, OsZIP5, and OsZIP8 could be involved in root to shoot translocation (Bashir et al, 2013).…”

Improved yield and Zn accumulation for rice grain by Zn fertilization and optimized water management

“…However, zinc (Zn) deficiency in rice has been widely reported in many rice-growing regions of the world (Lonergan et al, 2009;Tiong et al, 2014). Zn deficiency in crop plants results in not only yield reduction but also Zn malnutrition in humans, where a high proportion of rice is consumed as a staple food (Wu et al, 2011;Chasapis et al, 2012).…”

Got to hide your Zn away: Molecular control of Zn accumulation and biotechnological applications

“…Low Zn concentrations in seeds were also observed with over-expression of OsZIP5 [41] and OsZIP8 [42]. Conversely, over-expression of AtZIP1 and HvZIP7 in barley led to up to 2.7-fold higher Zn concentrations in grains [43,172].…”

“…The barley HvZIP7 protein functions as a plasma membrane low-affinity Zn-specific transporter, and is expressed primarily in vascular tissues of roots and shoots. Over-expression of HvZIP7 resulted in increased Zn concentrations in leaves and seeds when plants were provided with moderately high, non-toxic, Zn supply [43].…”