Expression and Ion Transport Activity of Rice Variants.

in rice, belongs to the high-affinity K Transporter family, has been found to be involved in salt tolerance. in rice (Nipponbare) produces mRNA variants, but their functions remain elusive. In salt tolerant rice, Pokkali, eight variants (V1-V8) were identified in addition to the full-length (FL) cDNA. Absolute quantification by qPCR revealed that accumulation of mRNA is minor in contrast to that of , , , and mRNAs, all of which are predominant in shoots, while only and mRNAs are predominant in roots. Two electrode voltage clamp (TEVC) experiments using oocytes revealed that oocytes-expressing OsHKT1;1-FL from Pokkali exhibited inward-rectified currents in the presence of 96 mM Na as reported previously. Further TEVC analyses indicated that six of eight OsHKT1;1 variants elicited currents in a Na or a K bath solution. OsHKT1;1-V6 exhibited a similar inward rectification to the FL protein. Contrastingly, however, the rests mediated bidirectional currents in both Na and K bath solutions. These data suggest possibilities that novel mechanisms regulating the transport activity of OsHKT1;1 might exist, and that OsHKT1;1 variants might also carry out distinct physiological roles either independently or in combination with OsHKT1;1-FL.