Os05g0574500

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OsRAN2 is a member of Ran(Ras-related nuclear protein) gene, which is a small nuclear GTP binding protein[1][2].

Annotated Information

Gene Symbol

  • Os05g0574500 <=> OsRAN2, RAN2

Function

  • OsRAN2(Os05g0574500) negatively responds to abiotic stress stimulus and OsRAN2 overexpression caused transformants hypersensitive to abiotic stress[1].
  • Reduced RANs (RAN1 and RAN2) transcriptional expression may cause an abnormal Ran GTPase cycle, including abnormal nuclear trafficking and abnormal mitotic spindle or nuclear envelope assembly, which finally may result in male sterility and other developmental defects in RANi plants[1]. Plant Ran GTPase may have an important role in connecting cell division with cold stress signalling in rice. Ran GTPase may have a conserved function in cell cycle regulation[2]. Small GTPases may act as important molecular switches associated with plant signaling[3].
  • CHEN et al. suggests a mechanism for OsRAN2 in regulating cold resistance in rice by maintaining cell division through promoting the normal export of intranuclear tubulin at the end of mitosis. This insight could help improve the cold-tolerance trait in rice. OsRAN2 may be essential for spindle formation in the mitotic process in rice.
  • The regulation of OsRAN2 in cell division may be through the following mechanism: in the mitotic phase, OsRAN2 co-localizes with the spindle and provides a spatial signal for cell division, and at the end of mitosis, OsRAN2 may also have a role in promoting the assembly of an intact NE under cold stress. OsRAN2 enhanced cold tolerance by maintaining active cell division through regulating the formation of an intact NE under cold stress in rice. Plant Ran homologs may have well-conserved functions in plants, yeast and animals during evolution[2].

GO assignment(s): GO:0000178, GO:0005525, GO:0005622, GO:0006886, GO:0007264

Mutation

  • Homozygous transgenic T2
  • Zhonghua11 (control) seeds
  • 11 transgenic rice lines[1]:

An RNA molecular marker transcribed from the fused fragments is capable of forming a dsRNA stem with a single-stranded terminal loop, a structure that can potentially induce silencing of the OsRAN2 by the RNAi mechanism. Eleven transgenic rice lines were generated and confirmed by genomic PCR.

  • transgenic lines overexpressing(OE)[2]:
    • OE1, OE5, OE15, OE16, OE17, OE18, OE20
  • Knockdown transgenic rice lines showed an aberrant organization of spindles during mitosis and stunted growth during development.
  • OsRAN2 RNAi transgenic plants[2]:
    • R29
    • R32

Expression

  • Transcription of OsRAN2 was reduced by salt, osmotic, and exogenous abscisic acid (ABA) treatments, as determined by real-time PCR[1]. OsRAN2 predominantly responded to low temperature as compared with salt and drought stress. Expression of OsRAN2 was increased under cold treatment, but not during salt and drought stress. The mean root mitotic index was closely related to the expression level of OsRAN2[2].
  • OsRAN2 overexpression in rice and Arabidopsis caused enhanced sensitivity to ABA, salinity, or osmotic stress treatments. Its' overexpression in plants disturbs nuclear import and resulted in enhanced sensitivity to salinity, osmotic stress, and ABA. Seedlings of transgenic Arabidopsis thaliana plants overexpressing OsRAN2 were overly sensitive to salinity stress and exogenous ABA treatment[1]. Overexpression of OsRAN2 enhanced cold tolerance in rice. The transgenic rice overexpressing OsRAN2 showed maintained cell division, decreased proportion of cells with intranuclear tubulin and formation of a normal nuclear envelope under the cold condition. Overexpression of OsRAN2 may promote the formation of an intact NE under cold stress[2].
  • Gene-silenced rice plants generated via RNA interference (RNAi) displayed pleiotropic developmental abnormalities and were male sterile[1].

Subcellular localization

The subcellular localization of OsRAN2:GFP was examined through transient expression of OsRAN2:GFP in onion epidermal cells. Subcellular localization results showed that OsRan2 is mainly localized in the nucleus, with some in the cytoplasm[1].

Evolution

Figure 1. Phylogenetic analysis of plant Ran GTPase.(from reference [2]).
Figure 2. Phylogenetic tree analysis of small G proteins.(from reference [4]).
  • The predicted protein sequence of OsRAN2 was aligned with related sequences from Arabidopsis (AtRan1, AtRan2, AtRan3, and AtRan4), wheat (TaRan1), and human (Ran/TC4). The alignment showed high sequence homology, 77% at the amino acid level, between OsRan2 and its human counterpart. The characteristic domains of the Ran proteins known to be involved in GTP-binding and hydrolysis, as well as the acidic C-terminal domain and the effector-binding domain have been highly conserved in most Ran proteins of different organisms[1].
  • CHEN et al. explored the amino acid similarity of plant Ran GTPases by phylogenetic analysis (Fig. 1). Plant Ran GTPases have more than 95% amino acid identity. However, Ran GTPases of monocotyledons such as maize, wheat and rice show higher similarity. TaRAN1 has been shown to promote the cell mitosis transition in rice[3]. Phylogenetic analysis revealed that of the two rice RAN proteins, OsRAN2 is nearer to TaRAN1 than is OsRAN1[2][3].
  • Phylogenetic trees based on the full-length amino acid sequences of MfARL1 proteins were constructed using the MEGA 5 software (Fig. 2)[4]. The resulting trees contained four families, Rab, Ran, Rop and Arf. According to the phylogenetic trees, OsRAN2 belongs to the Ran[4].

Knowledge Extension

Figure 3. Organization of Ran regulators in mitosis.(from reference [5]).
  • The small GTPase Ran has roles in nuclear transport, mitotic spindle assembly and nuclear envelope assembly. The control of Ran within the mitotic spindle could be remarkably complex (Figure 3)[5]. Near chromosomes, RCC1 generates Ran–GTP that in turn regulates microtubule dynamics. At kinetochores and on spindles, RanGAP mediates Ran–GTP hydrolysis[5].
  • Nucleo-cytoplasmic partitioning of regulatory proteins is increasingly being recognized as a major control mechanism for the regulation of signalling in plants. Ras-related nuclear protein (Ran) GTPase is required for regulating transport of proteins and RNA across the nuclear envelope and also has roles in mitotic spindle assembly and nuclear envelope (NE) assembly. However, thus far little is known of any Ran functions in the signalling pathways in plants in response to changing environmental stimuli[1].
  • The protein Ran is a member of an important family of small GTPases that control multiple cellular processes, including the trafficking of proteins and RNAs into and out of the nucleus[6] and the assembly of the mitotic spindle and nuclear envelope (NE)[5][6][7][8]. Ran is GDP-bound in the cytoplasm during interphase and GTP-bound in the nucleus. it has been shown that Ran and RanBPs are considered to be involved in the regulation of hormone sensitivities, light signalling, and resistance to pathogens.
  • The small GTPase superfamily is divided into the five families Ras, Rho, Rab, Arf and Ras-like nuclear GTPase (Ran). Ran is an abundant nuclear small GTPase[9]

Labs working on this gene

  • Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China
  • Centre for Research in Plant Science, University of the West of England, Bristol BS16 1QY, UK
  • Research Center for Molecular and Developmental Biology, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
  • State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100094, China

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Zang A, Xu X, Neill S, et al. Overexpression of OsRAN2 in rice and Arabidopsis renders transgenic plants hypersensitive to salinity and osmotic stress[J]. Journal of experimental botany, 2009: erp341.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Chen N A, Xu Y, Wang X, et al. OsRAN2, essential for mitosis, enhances cold tolerance in rice by promoting export of intranuclear tubulin and maintaining cell division under cold stress[J]. Plant, cell & environment, 2011, 34(1): 52-64.
  3. ↑ 3.0 3.1 3.2 Wang X, Xu Y, Han Y, et al. Overexpression of RAN1 in rice and Arabidopsis alters primordial meristem, mitotic progress, and sensitivity to auxin[J]. Plant Physiology, 2006, 140(1): 91-101.
  4. ↑ 4.0 4.1 4.2 Wang T Z, Xia X Z, Zhao M G, et al. Expression of a< i> Medicago falcata</i> small GTPase gene,< i> MfARL1</i> enhanced tolerance to salt stress in< i> Arabidopsis thaliana</i>[J]. Plant Physiology and Biochemistry, 2013, 63: 227-235.
  5. ↑ 5.0 5.1 5.2 5.3 Quimby B B, Dasso M. The small GTPase Ran: interpreting the signs[J]. Current opinion in cell biology, 2003, 15(3): 338-344.
  6. ↑ 6.0 6.1 Görlich D, Kutay U. Transport between the cell nucleus and the cytoplasm[J]. Annual review of cell and developmental biology, 1999, 15(1): 607-660.
  7. ↑ Di Fiore B, Ciciarello M, Lavia P. Mitotic Functions of the Ran GTPase Network: the Importance of Being in the Right Place at the Right Time[J]. Cell Cycle, 2003, 3(3): 303-311.
  8. ↑ Ciciarello M, Mangiacasale R, Lavia P. Spatial control of mitosis by the GTPase Ran[J]. Cellular and molecular life sciences, 2007, 64(15): 1891-1914.
  9. ↑ Drivas G T, Shih A, Coutavas E, et al. Characterization of four novel ras-like genes expressed in a human teratocarcinoma cell line[J]. Molecular and Cellular Biology, 1990, 10(4): 1793-1798.

Structured Information

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