Abstract
OsHKT1;1 in rice, belongs to the high-affinity K+ Transporter family, has been found to be involved in salt tolerance. OsHKT1;1 in japonica rice (Nipponbare) produces mRNA variants, but their functions remain elusive. In salt tolerant rice, Pokkali, eight OsHKT1;1 variants (V1-V8) were identified in addition to the full-length OsHKT1;1 (FL) cDNA. Absolute quantification by qPCR revealed that accumulation of OsHKT1;1-FL mRNA is minor in contrast to that of OsHKT1;1-V1, -V2, -V4, and -V7 mRNAs, all of which are predominant in shoots, while only V1 and V7 mRNAs are predominant in roots. Two electrode voltage clamp (TEVC) experiments using Xenopus laevis 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.
Highlights
Salinity affects plant growth and development and causes low crop productivity [1]
Upon the coding DNA (cDNA) isolation using primers for the full-length clone, several different fragments were amplified from the first strand population prepared from the whole seedling of a salt tolerant indica variety Pokkali (Figure 1A)
Under salt stress several Na+ transporters play an essential role in Na+ tolerance in plants
Summary
Salinity affects plant growth and development and causes low crop productivity [1]. Salinity can give rise to osmotic stress, nutritional imbalance, and ionic toxicity in the plant [2,3]. Rice (Oryza sativa) is the most sensitive to salinity stress [2,4]. The high-affinity K+ transporter (HKT) gene family has been found to be relevant to salt stress tolerance in plants [5,6]. HKTs can be classified into at least two subfamilies [5,8]
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