Halophytic HbHAK1 Facilitates Potassium Retention and Contributes to Salt Tolerance

Potassium retention under saline conditions has emerged as an important determinant for salt tolerance in plants. Halophytic evolves better strategies to retain K to improve high-salt tolerance. Hence, uncovering K-efficient uptake under salt stress is vital for understanding K homeostasis. HAK/KUP/KT transporters play important roles in promoting K uptake during multiple stresses. Here, we obtained nine salt-induced HAK/KUP/KT members in with different expression patterns compared with through transcriptomic analysis. One member HbHAK1 showed high-affinity K transporter activity in to cope with low-K or salt stresses. The expression of HbHAK1 in yeast Cy162 strains exhibited strong activities in K uptake under extremely low external K conditions and reducing Na toxicity to maintain the survival of yeast cells under high-salt-stress. Comparing with the sequence of barley HvHAK1, we found that C170 and R342 in a conserved domain played pivotal roles in K selectivity under extremely low-K conditions (10 μM) and that A13 was responsible for the salt tolerance. Our findings revealed the mechanism of HbHAK1 for K accumulation and the significant natural adaptive sites for HAK1 activity, highlighting the potential value for crops to promote K-uptake under stresses.