Figure 5

Functions of HKT transporters in higher plants. The transporters of HKT2;1-like, including OsHKT2;1, HvHKT2;1 and TaHKT2;1, mediate Na⁺ uptake from culturing media merely in K⁺-starved environments. HKT transporters, such as AtHKT1;1, OsHKT1;5, TaHKT1;5-D, TmHKT1;4-A2 and TmHKT1;5-A are involved in Na⁺ exclusion from xylem to xylem parenchyma cell in order to minimize the accumulation of Na⁺ in the shoot through the transpiration stream, and this is the key process for salinity tolerance of plants. OsHKT2;4 is a very special member in HKT family, and it is not only conducts as a transporter of Na⁺-K⁺ symport but also mediate Ca²⁺ (maybe other divalent cations) uptake like a cation channel. Cell types depicted include: epidermal cell (EPC), cortical cell (COC), endodermis cell (ENC), pericycle cell (PEC), parenchyma cell (PAC).