Gene Details:

Functional Descriptions:

  • Here we present a review on vital physiological functions of HKT transporters including AtHKT1;1 and OsHKT1;5 in preventing shoot Na(+) over-accumulation by mediating Na(+) exclusion from xylem vessels in the presence of a large amount of Na(+) thereby protecting leaves from salinity stress.
  • We previously mapped a rice QTL, SKC1, that maintained K(+) homeostasis in the salt-tolerant variety under salt stress, consistent with the earlier finding that K(+) homeostasis is important in salt tolerance.
  • Physiological analysis suggested that SKC1 is involved in regulating K(+)/Na(+) homeostasis under salt stress, providing a potential tool for improving salt tolerance in crops.
  • SKC1 is preferentially expressed in the parenchyma cells surrounding the xylem vessels.
  • The association of leaf Na+ concentrations with cultivar-groups was very weak, but association with the OsHKT1;5 allele was generally strong.
  • Seven major and three minor alleles of OsHKT1;5 were identified, and their comparisons with the leaf Na+ concentration showed that the Aromatic allele conferred the highest exclusion and the Japonica allele the least.
  • In addition, lower expression of OsHKT1;5 and OsSOS1 in old leaves may decrease frequency of retrieving Na+ from old leaf cells.
  • To understand the molecular basis of this QTL, we isolated the SKC1 gene by map-based cloning and found that it encoded a member of HKT-type transporters.
  • Voltage-clamp analysis showed that SKC1 protein functions as a Na(+)-selective transporter.
  • For OsHKT1;5, both transcript abundance and protein structural features within the selectivity filter could control shoot Na(+) accumulation in a range of rice varieties.
  • OsHKT1;5 mediates Na(+) exclusion in the vasculature to protect leaf blades and reproductive tissues from salt toxicity in rice.
  • Additionally, direct introduction of (22) Na(+) tracer to leaf sheaths also demonstrated the involvement of OsHKT1;5 in xylem Na(+) unloading in leaf sheaths.
  • Together with the characteristic (22) Na(+) allocation in the blade of the developing immature leaf in the mutants, these results suggest a novel function of OsHKT1;5 in mediating Na(+) exclusion in the phloem to prevent Na(+) transfer to young leaf blades.
  • Our findings further demonstrate that the function of OsHKT1;5 is crucial over growth stages of rice, including the protection of the next generation seeds as well as of vital leaf blades under salt stress.
  • Immuno-staining using an anti-OsHKT1;5 peptide antibody indicated that OsHKT1;5 is localized in cells adjacent to the xylem in roots.
  • Furthermore, OsHKT1;5 was indicated to present in the plasma membrane and found to localize also in the phloem of diffuse vascular bundles in basal nodes.
  • Salt tolerance QTL analysis of rice has revealed that the SKC1 locus, which is involved in a higher K(+) /Na(+) ratio in shoots, corresponds to the OsHKT1;5 gene encoding a Na(+) -selective transporter.
  • However, physiological roles of OsHKT1;5 in rice exposed to salt stress remain elusive and no OsHKT1;5 gene disruption mutants have been characterized to date.
  • Salt stress-induced increases in the OsHKT1;5 transcript was observed in roots and basal stems including basal nodes.
  • We also report the development and validation of a new Cleavage Amplified Polymorphic Sequence (CAPS) marker (OsHKT1;5V395) that targets a codon in the sodium transporter gene OsHKT1;5 (Saltol/SKC1 locus) that is associated with sodium transport rates in the above rice landraces.
  • Analysis of genetic diversity and population structure using SSR markers and validation of a Cleavage Amplified Polymorphic Sequences (CAPS) marker involving the sodium transporter OsHKT1;5 in saline tolerant rice (Oryza sativa L.) landraces.
  • Allelic variation in rice OsHKT1;5 sequence in specific landraces (Nona Bokra OsHKT1;5-NB/Nipponbare OsHKT1;5-Ni) correlates with variation in salt tolerance.
  • In rice, the OsHKT1;5 gene has been reported to be a critical determinant of salt tolerance.
  • Changes in Expression Level of OsHKT1;5 Alters Activity of Membrane Transporters Involved in K + and Ca 2+ Acquisition and Homeostasis in Salinized Rice Roots.
  • Furthermore, expression analysis suggested that OsGrx_C7 acted as positive regulator of salt tolerance by reinforcing the expression of transporters (OsHKT2;1, OsHKT1;5 and OsSOS1) engaged in Na+ homeostasis in overexpressing plants.
  • Intriguingly, salt stress facilitates the nuclear relocation of OsDNAJ15 so that it can interact with OsBAG4, and OsDNAJ15 and OsBAG4 synergistically facilitate the DNA-binding activity of OsMYB106 to positively regulate the expression of OsHKT1;5.
  • Using a previously generated high-throughput activation tagging-based T-DNA insertion mutant pool, we isolated a mutant exhibiting salt stress-sensitive phenotype, caused by a reduction in OsHKT1;5 transcripts.
  • Plasma membrane-localized Hsp40/DNAJ chaperone protein facilitates OsSUVH7-OsBAG4-OsMYB106 transcriptional complex formation for OsHKT1;5 activation.
  • The real-time quantitative PCR (qRT-PCR) and transcriptome analysis revealed that OsWRKY54 regulated the expression of some essential genes related to salt tolerance, such as OsNHX4 and OsHKT1;5.

Literature:

Gene Resources:

Sequences:

cDNA Sequence
  • >LOC_Os01g20160.1
    GCTGTTGCTCTTGTTCACTTGTGCTCACAGCACCTGGTAACCCCACATACAGTGATCACACAACAAACAATATCTGTTGTTTGTGTATAAATAGCCCTAACATGGCTTCCTAATTCCTATAAACAACAAGTGTGAGAAAACCCAAGAACGAAACACATAGGAGAGAAATGAGTTCTCTGGATGCCACTACTCCTAGATATGACGAGTTTAAAAGGATCTACCACCTTTTCCTTTTCCATGCACACCCATTCTGGCTCCAACTGCTGTACTTCCTCTTCATCTCCCTCTTGGGTTTCTTGATGCTGAAAGCTCTGCCGATGAAGACCAGCATGGTGCCGAGGCCCATGGACTTGGACCTGATCTTCACGTCGGTGTCGGCGACGACGGTGTCGAGCATGGTCGCCGTCGAGATGGAGTCCTTCTCCAACTCCCAGCTCCTCCTCATCACCCTCCTCATGCTGCTTGGTGGTGAGGTCTTCACCAGCATCCTTGGCCTCTACTTCACCAACGCCAAGTACTCCTCCAAGATGATAGCAACCTTACCTGATGATGACGACCATGGTGGCAGTGGCAAACCACCACCACCAACGACGTCACCTTCGTCTACCCTAGTGGAGCTCGAGCTCGCTCCTCCCATGGACGTCGTCGTCGTCAACCCTACCACCACTGCGACGACGCACGACGAGGTAGAGCTAGGGTTAGGACGTCGGAACAAGCGCGGCTGCACCTGCACTACTACTCACACGTCGTCGTCATCATCGGCATCGAAGACGACGACGACGAGGCTACTGATGTTCGTGGTGATGGGGTACCACGCGGTGGTGCACGTCGCCGGGTACACGGCCATCGTCGTGTACCTCAGCGCCGTCGGCGGCGCGGGGGCGGTGGTCGCCGGGAAGGGGATCAGCGCGCACACGTTCGCCATCTTCACCGTCGTCTCGACGTTCGCCAACTGCGGGTTCGTGCCGACGAACGAAGGGATGGTGTCGTTCAGGTCGTTCCCGGGGCTCCTCCTCCTCGTCATGCCGCACGTCCTCCTCGGGAACACGCTCTTCCCGGTCTTCCTCAGGCTGGCCATCGCCGCGCTCGAGAGGGTCACCGGGTGGCCGGAGCTCGGCGAGCTCCTGATCCGGCGGCGGAGGGGCGGCGGCGAGGGCTACCACCACCTGTTGCCGAGCTCGCGCACGCGGTTCCTGGCCCTCACCGTGGCCGTGCTCGTGGTGGCGCAGCTGGCGCTCTTCTGCGCCATGGAGTGGGGCTCCGACGGGCTGCGGGGGCTCACCGCGGGCCAGAAGCTCGTCGGCGCGCTCTTCATGGCGGTCAACTCGAGGCACTCCGGTGAGATGGTGCTCGACCTCTCCACCGTGTCGTCGGCCGTCGTCGTGCTCTACGTGGTGATGATGTACCTGCCACCTTACACCACTTTCGTACCTGTCCAAGACAAACACCAGCAAACGGGAGCACAGTCCGGGCAGGAGGGCAGCAGCAGCAGCAGCATATGGCAGAAGCTGCTCATGTCGCCGCTCTCGTGCCTAGCCATCTTCATCGTCGTCATCTGCATCACGGAGCGGCGGCAAATCGCCGACGACCCCATCAACTACAGCGTCCTCAACATCGTCGTCGAGGTTATCAGTGCGTATGGCAATGTGGGGTTCAGCACGGGGTACAGCTGCGCGAGGCAGGTGAGGCCCGACGGCAGCTGCAGAGACCTGTGGGTTGGCTTCTCAGGGAAGTGGAGCAAACAAGGGAAGCTCACTCTCATGGCCGTCATGTTCTACGGCAGGCTCAAGAAGTTCAGCCTGCACGGTGGTCAGGCATGGAAGATAGAATAACGCCTAACTGCAAGCACCCATGCATGCATGACAACTTCGTTACTAATTAATGGGGCATTTCAGCCGGCCGCCGTACTAGACTACAAGAGATCGATCGATAGGTCTCCCCTCCTAAAACTCCTCCTTAATCTGATCTCCACGAGTTCTTGATCAGGGTTACTTATATATTATAAAGGAATGATCAGATAAATATATGTCTATATCAGGATCTGGTCGATCTCTAGATATCTGTCTTTTTTTTTTTTGGGTAATGCATGTAAGCAAGTAGCAATTGCTAGACATATATATGTGTTAGCTTACGAGAGTATATACTGGCGCTTGAGTCGTGATGA
CDS Sequence
  • >LOC_Os01g20160.1
    ATGAGTTCTCTGGATGCCACTACTCCTAGATATGACGAGTTTAAAAGGATCTACCACCTTTTCCTTTTCCATGCACACCCATTCTGGCTCCAACTGCTGTACTTCCTCTTCATCTCCCTCTTGGGTTTCTTGATGCTGAAAGCTCTGCCGATGAAGACCAGCATGGTGCCGAGGCCCATGGACTTGGACCTGATCTTCACGTCGGTGTCGGCGACGACGGTGTCGAGCATGGTCGCCGTCGAGATGGAGTCCTTCTCCAACTCCCAGCTCCTCCTCATCACCCTCCTCATGCTGCTTGGTGGTGAGGTCTTCACCAGCATCCTTGGCCTCTACTTCACCAACGCCAAGTACTCCTCCAAGATGATAGCAACCTTACCTGATGATGACGACCATGGTGGCAGTGGCAAACCACCACCACCAACGACGTCACCTTCGTCTACCCTAGTGGAGCTCGAGCTCGCTCCTCCCATGGACGTCGTCGTCGTCAACCCTACCACCACTGCGACGACGCACGACGAGGTAGAGCTAGGGTTAGGACGTCGGAACAAGCGCGGCTGCACCTGCACTACTACTCACACGTCGTCGTCATCATCGGCATCGAAGACGACGACGACGAGGCTACTGATGTTCGTGGTGATGGGGTACCACGCGGTGGTGCACGTCGCCGGGTACACGGCCATCGTCGTGTACCTCAGCGCCGTCGGCGGCGCGGGGGCGGTGGTCGCCGGGAAGGGGATCAGCGCGCACACGTTCGCCATCTTCACCGTCGTCTCGACGTTCGCCAACTGCGGGTTCGTGCCGACGAACGAAGGGATGGTGTCGTTCAGGTCGTTCCCGGGGCTCCTCCTCCTCGTCATGCCGCACGTCCTCCTCGGGAACACGCTCTTCCCGGTCTTCCTCAGGCTGGCCATCGCCGCGCTCGAGAGGGTCACCGGGTGGCCGGAGCTCGGCGAGCTCCTGATCCGGCGGCGGAGGGGCGGCGGCGAGGGCTACCACCACCTGTTGCCGAGCTCGCGCACGCGGTTCCTGGCCCTCACCGTGGCCGTGCTCGTGGTGGCGCAGCTGGCGCTCTTCTGCGCCATGGAGTGGGGCTCCGACGGGCTGCGGGGGCTCACCGCGGGCCAGAAGCTCGTCGGCGCGCTCTTCATGGCGGTCAACTCGAGGCACTCCGGTGAGATGGTGCTCGACCTCTCCACCGTGTCGTCGGCCGTCGTCGTGCTCTACGTGGTGATGATGTACCTGCCACCTTACACCACTTTCGTACCTGTCCAAGACAAACACCAGCAAACGGGAGCACAGTCCGGGCAGGAGGGCAGCAGCAGCAGCAGCATATGGCAGAAGCTGCTCATGTCGCCGCTCTCGTGCCTAGCCATCTTCATCGTCGTCATCTGCATCACGGAGCGGCGGCAAATCGCCGACGACCCCATCAACTACAGCGTCCTCAACATCGTCGTCGAGGTTATCAGTGCGTATGGCAATGTGGGGTTCAGCACGGGGTACAGCTGCGCGAGGCAGGTGAGGCCCGACGGCAGCTGCAGAGACCTGTGGGTTGGCTTCTCAGGGAAGTGGAGCAAACAAGGGAAGCTCACTCTCATGGCCGTCATGTTCTACGGCAGGCTCAAGAAGTTCAGCCTGCACGGTGGTCAGGCATGGAAGATAGAATAA
Protein Sequence
  • >LOC_Os01g20160.1
    MSSLDATTPRYDEFKRIYHLFLFHAHPFWLQLLYFLFISLLGFLMLKALPMKTSMVPRPMDLDLIFTSVSATTVSSMVAVEMESFSNSQLLLITLLMLLGGEVFTSILGLYFTNAKYSSKMIATLPDDDDHGGSGKPPPPTTSPSSTLVELELAPPMDVVVVNPTTTATTHDEVELGLGRRNKRGCTCTTTHTSSSSSASKTTTTRLLMFVVMGYHAVVHVAGYTAIVVYLSAVGGAGAVVAGKGISAHTFAIFTVVSTFANCGFVPTNEGMVSFRSFPGLLLLVMPHVLLGNTLFPVFLRLAIAALERVTGWPELGELLIRRRRGGGEGYHHLLPSSRTRFLALTVAVLVVAQLALFCAMEWGSDGLRGLTAGQKLVGALFMAVNSRHSGEMVLDLSTVSSAVVVLYVVMMYLPPYTTFVPVQDKHQQTGAQSGQEGSSSSSIWQKLLMSPLSCLAIFIVVICITERRQIADDPINYSVLNIVVEVISAYGNVGFSTGYSCARQVRPDGSCRDLWVGFSGKWSKQGKLTLMAVMFYGRLKKFSLHGGQAWKIE*