Point mutations in the barley HvHAK1 potassium transporter lead to improved K+-nutrition and enhanced resistance to salt stress

Members of group I KT-HAK-KUP transporters play an important role in K+ acquisition by plant roots, a process that is strongly affected by salt stress. A PCR-based random mutagenesis approach on HvHAK1 allowed identification of V366I and R591C substitutions, which confer enhanced K+-capture, and improved NaCl, LiCl and NH4Cl tolerance, to yeast cells. Improved K+-capture was linked to an enhanced Vmax. Results reveal an intrinsic protective effect of K+, and assign an important role to the 8th transmembrane domain, as well as the C-terminus, in determining the maximum capacity for the transport of K+ in KT-HAK-KUP transporters.