Abstract
High accumulation of silicon (Si) in the shoots including leaves and grains is required for protecting the plants from biotic and abiotic stresses. Silicon uptake by the roots is mediated by an influx transporter HvLsi1 and an efflux transporter HvLsi2 in barley. However, the transporters involved in the distribution of Si in the shoots have not been identified in barley. Here, we report that HvLsi6 and HvLsi2 are involved in the Si distribution. HvLsi6 is a homolog of HvLsi1, but expressed in the leaf blades, leaf sheaths and nodes in addition to the roots. In the roots, HvLsi6 is expressed in all cells, but in the leaf blades and sheaths, HvLsi6 is only localized at parenchyma cells of xylem vessels. At the node, it is located at the transfer cells surrounding the enlarged vascular bundles. On the other hand, HvLsi2 is localized at the parenchyma cell layer adjacent to the transfer cells with opposite polarity of HvLsi6. These results suggest that HvLsi6 is involved in xylem unloading of Si in leaf blade and sheath. In addition, both HvLsi6 and HvLsi2 are involved in inter-vascular transfer of Si at the nodes from enlarged vascular bundles to diffuse vascular bundles.
