Foxtail millet SiHAK1 excites extreme high-affinity K + uptake to maintain K + homeostasis under low K + or salt stress

Key message This is the first evidence that SiHAK1 acts as a K+ transporter and is modulated by internal and external K+, which expands our understanding of the significant physiological roles of large HAK/KUP/KT transporters in crops.