A Survey of Barley PIP Aquaporin Ionic Conductance Reveals Ca-Sensitive Na and K Conductance.

Some plasma membrane intrinsic protein (PIP) aquaporins can facilitate ion transport. Here we report that one of the 12 barley PIPs (PIP1 and PIP2) tested, , facilitated cation transport when expressed in oocytes. -associated ion currents were detected with Na and K, but not Cs, Rb, or Li, and was inhibited by Ba, Ca, and Cd and to a lesser extent Mg, which also interacted with Ca. Currents were reduced in the presence of K, Cs, Rb, or Li relative to Na alone. Five HvPIP1 isoforms co-expressed with inhibited the ion conductance relative to alone but HvPIP1;3 and HvPIP1;4 with maintained the ion conductance at a lower level. water permeability was similar to that of a C-terminal phosphorylation mimic mutant S285D, but S285D showed a negative linear correlation between water permeability and ion conductance that was modified by a kinase inhibitor treatment. transcript abundance increased in barley shoot tissues following salt treatments in a salt-tolerant cultivar Haruna-Nijo, but not in salt-sensitive I743. There is potential for to be involved in barley salt-stress responses, and could facilitate both water and Na/K transport activity, depending on the phosphorylation status.