Os11g0648000

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OsNHX3(Os11g0648000), is a Na+‡and H+‡exchanger in rice (Oryza sativa)[1].

Annotated Information

Function

Figure 1. Genomic organization of the OsNHX3 genes.(from reference [1]).
  • OsNHX3 can suppress the Na+, Li+, and hygromycin sensitivity of yeast nhx1 mutants and their sensitivity to a high K+ concentration. The expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 is regulated differently in rice tissues and is increased by salt stress, hyperosmotic stress, and ABA[1].
  • The genomic organization of OsNHX3 is graphically presented in Figure 1. OsNHX3 had 15 exons[1].

GO assignment(s): GO:0006814, GO:0006885, GO:0015299, GO:0015385, GO:0016021

Expression

Figure 2. Expression of OsNHX1, 2, 3, and 5 in rice tissues.(from reference [1]).

Fukuda et al. examined the expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 in various rice tissues by Northern-blot analysis with total RNA extracted from 8-day-old rice seedlings and 12-weekold rice (7 days after heading). Expression of these genes was regulated differently in different rice tissues (Fig. 2). Compared with other tissues, those of OsNHX3 were higher in flag leaf sheaths and blades [1]

  • Treatment with salt stress, hyperosmotic stress (mannitol), and ABA increased the transcript levels of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 in rice seedlings[1].
  • Treatment with high concentrations of KCl scarcely changed transcript levels of OsNHX3 (Fig. 5b). In Figure 3, OsNHX3-mediated less K+ tolerance than the other family genes in yeast mutants. These results suggest that OsNHX3 might have low transport capacity of K+ and not function in the tolerance of rice seedlings to high concentrations of KCl[1].
  • The expression of OsNHX1, OsNHX2, OsNHX3, and OsNHX5 might be regulated through different ABA-dependent pathways[1].

Evolution

Figure 3. Phylogenetic analysis of Na+/H+ antiporter proteins.(from reference [1]).
Figure 4. Phylogenetic tree of intracellular NHE/NHX exchangers.(from reference [2]).
  • The OsNHX proteins shared between 29 and 75% identity. OsNHX1 through 4 in particular shared high similarity, with more than 70% identity among OsNHX1 through 3 and more than 50% identity among OsNHX1 through 4. The sequence of LFFIYLLPPI, which is identified as the binding site of amiloride, an inhibitor of eukaryotic Na+/H+ antiporters, was identical among OsNHX1 through 3 and highly conserved in OsNHX4 and 5. The membrane-spanning segments M5 and M6 of OsNHX1, which are well conserved in the eukaryotic Na+/H+ antiporters, also shared high similarity with OsNHX2 through 5, and all of the OsNHX proteins contained the residues important for Na+/H+ antiport activity[3][4].
  • OsNHX1 through 4, AtNHX1 through 4, and other most plant NHXtype antiporters are classified into a type I group, and OsNHX5, AtNHX5, AtNHX6, and LeNHX2 from L. esculentum are classified into the type II group (Fig. 3)[1].
  • Arabidopsis contains six NHX genes and rice has five, which are distributed in a similar way: AtNHX1–4 and OsNHX1–4 constitute class

I, and AtNHX5–6 and OsNHX5 constitute class II (Fig. 4). Members of the class-I category of Arabidopsis and rice show 54–87% similarity. Similarity among class-II members is 72–79%, but they are only 21–23% similar to class-I isoforms. These data indicate that divergence between class-I and class-II exchangers in plants occurred before the separation of dicotyledons and monocotyledons[3].

  • Pires et al. observe that multiple independent duplication events have occurred throughout the evolutionary history of the NHX family. Based on the reconciled phylogeny, Pires et al. estimate 27 independent gene duplication and 40 gene loss events during the diversification of this gene family[5].

Knowledge Extension

  • The Na+/H+‡exchanger that catalyzes the exchange of Na+‡for H+‡across membranes, contributes to regulation of internal pH, cell volume, and sodium level in the cytoplasm)[6].
  • Na+/H+ antiporters, which catalyze the exchange of Na+ for H+ across membranes, contribute to the regulation of internal pH, cell volume and the sodium level in the cytoplasm[7][8]. The antiporters are widespread membrane proteins found in animals, yeasts, bacteria and plants. In particular, vacuolar Na+/H+ antiporters, which compartmentalize Na+ into the vacuoles for detoxification, have been investigated as the key to salt tolerance in yeasts and plants[9].

Labs working on this gene

  • Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan
  • Graduate School of Life and Environmental Sciences, Tsukuba University, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan
  • Instituto de Recursos Naturales y Agrobiologı´a, Consejo Superior de Investigaciones Cientı´ficas, Reina Mercedes 10, Sevilla 41012, Spain
  • Department of Biology and Center for Genomics and Systems Biology, New York University, New York, US

References

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Fukuda A, Nakamura A, Hara N, et al. Molecular and functional analyses of rice NHX-type Na+/H+ antiporter genes[J]. Planta, 2011, 233(1): 175-188.
  2. Pardo J M, Cubero B, Leidi E O, et al. Alkali cation exchangers: roles in cellular homeostasis and stress tolerance[J]. Journal of Experimental Botany, 2006, 57(5): 1181-1199.
  3. 3.0 3.1 Bowers K, Levi B P, Patel F I, et al. The sodium/proton exchanger Nhx1p is required for endosomal protein trafficking in the yeast Saccharomyces cerevisiae[J]. Molecular Biology of the Cell, 2000, 11(12): 4277-4294.
  4. Hamada A, Hibino T, Nakamura T, et al. Na+/H+ Antiporter fromSynechocystis Species PCC 6803, Homologous to SOS1, Contains an Aspartic Residue and Long C-Terminal Tail Important for the Carrier Activity[J]. Plant physiology, 2001, 125(1): 437-446.
  5. Pires I S, Negrão S, Pentony M M, et al. Different evolutionary histories of two cation/proton exchanger gene families in plants[J]. BMC plant biology, 2013, 13(1): 97.
  6. Orlowski J, Grinstein S. Na+/H+ exchangers of mammalian cells[J]. Journal of Biological Chemistry, 1997, 272(36): 22373-22376.
  7. Aronson P S. Kinetic properties of the plasma membrane Na+-H+ exchanger[J]. Annual Review of Physiology, 1985, 47(1): 545-560.
  8. Numata M, Orlowski J. Molecular cloning and characterization of a novel (Na+, K+)/H+ exchanger localized to the trans-Golgi network[J]. Journal of Biological Chemistry, 2001, 276(20): 17387-17394.
  9. Blumwald E, Aharon G S, Apse M P. Sodium transport in plant cells[J]. Biochimica et Biophysica Acta (BBA)-Biomembranes, 2000, 1465(1): 140-151.

Structured Information