Relative contribution of AtHAK5 and AtAKT1 to K uptake in the high-affinity range of concentrations

摘要

The relative contribution of the high-affinity K transporter AtHAK5 and the inward rectifier K channel AtAKT1 to K uptake in the high-affinity range of concentrations was studied in Arabidopsis thaliana ecotype Columbia (Col-0). The results obtained with wild-type lines, with T-DNA insertion in both genes and specific uptake inhibitors, show that AtHAK5 and AtAKT1 mediate the [graphic removed] -sensitive and the Bapo-sensitive components of uptake, respectively, and that they are the two major contributors to uptake in the high-affinity range of Rb concentrations. Using Rb as a K analogue, it was shown that AtHAK5 mediates absorption at lower Rb concentrations than AtAKT1 and depletes external Rb to values around 1 oM. Factors such as the presence of K or [graphic removed] during plant growth determine the relative contribution of each system. The presence of [graphic removed] in the growth solution inhibits the induction of AtHAK5 by K starvation. In K-starved plants grown without [graphic removed] , both systems are operative, but when [graphic removed] is present in the growth solution, AtAKT1 is probably the only system mediating Rb absorption, and the capacity of the roots to deplete Rb is reduced.