OsRAN1 is a member of Ran(Ras-related nuclear protein) gene, which is a small nuclear GTP binding protein.
- Ran gene OsRAN1 is essential for the molecular improvement of rice for cold tolerance. Ran also affect plant morphogenesis in transgenic Arabidopsis thaliana.
- Under cold stress, OsRAN1 maintained cell division and cell cycle progression, and also promoted the formation of an intact nuclear envelope, which suggesting that OsRAN1 protein plays an important role in the regulation of cellular mitosis and the auxin signalling pathway.
- OsRAN1 enhanced cold tolerance by maintaining cell division and regulating the intact NE(nuclear envelope) under cold stressin rice, both OsRAN1 and OsRAN2 may be involved in the organization of normal NE structures at the end of mitosis during the cold condition. OsRAN1 is involved in meristem cell proliferation in the root. Increased Pro and soluble sugar contents in OsRAN1 transgenic plants under cold stress.
- transgenic lines overexpressing(OE):
OE3, OE5, OE7, OE9, OE11, OE13, OE15, OE18, OE23, OE27, OE34, OE38, OE47, OE53, OE55, OE57
- The transgenic rice plants showed a tiller number up to 9.3 per plant on average. In contrast, wild-type rice had fewer tillers, about 7.3 per plant (Table 1).
- OsRAN1 is ubiquitously expressed in rice tissues with the highest expression in the spike. The levels of mRNA encoding OsRAN1 were greatly increased by cold and indoleacetic acid(IAA) treatment rather than by addition of salt and drought(polyethylene glycol). The expression of OsRAN1 is induced by jasmonic acid in rice.
- OsRAN1 overexpression in Arabidopsis increased tiller number, and altered root development. OsRAN1 overexpression in rice improves cold tolerance. The levels of cellular free Pro and sugar levels were highly increased in transgenic plants under cold stress.
- Overexpression of OsRAN1 increased tiller number and later flowering, and reduced apical dominance and abnormal roots in transgenic Arabidopsis, it controls development of shoots and the roots probably by affecting IAA signalling in the transgenic Arabidopsis.
Taken together, the overexpressing lines possessed more cells in the proliferation, especially under the cold condition, which suggesting that OsRAN1 overexpression increased mitosis. Overexpression of OsRAN1 protein might result in an abnormal or reduced rate of transport of important protein modulators to the nucleus. The OsRAN1-overexpressed transgenic plants are partly recovered by auxin, supporting the hypothesis that Ran was regulated by auxin and was involved in the auxin-mediated signalling pathway.
The subcellular localization of OsRAN1:GFP was traced to root cells of transgenic Arabidopsis steadily overexpressing OsRAN1 and tobacco epidermal cells expressing transiently. The green fluorescent signal of OsRAN1:GFP was detected mainly within the nucleus, with some signals in the hypocotyl cytoplasm, whereas the green fluorescent signal was randomly distributed in the cell under the GFP vector control.
The predicted protein sequence of OsRAN1 was aligned with related sequences from Arabidopsis (AtRan1, AtRan2, AtRan3, and AtRan4), wheat (OsRAN1), human (Ran/TC4), mouse (MusRan), Zea mays (ZmRan), and rice (OsRAN2, OsRAN3) (Fig. 1). The alignment showed 87% sequence homology between OsRAN1 and its human counterpart, and 95% homology between OsRAN1 and OsRAN2 at the amino acid level. The characteristic domains of the Ran proteins, which are known to be involved in GTP-binding and hydrolysis, in addition to the acidic C-terminal domain and the effector-binding domain, are highly conserved in most Ran proteins of various organisms.
- Phylogenetic trees based on the full-length amino acid sequences of MfARL1 proteins were constructed using the MEGA 5 software (Fig. 2). The resulting trees contained four families, Rab, Ran, Rop and Arf. According to the phylogenetic trees, OsRAN2 belongs to the Ran.
- 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.
- Ran proteins play an important role in nuclear transport. Ran is encoded by a family of four genes in Arabidopsis and three genes in rice. Ran, an evolutionarily conserved small G-protein family, has been shown to be essential for the nuclear translocation of proteins. It also mediates the regulation of cell cycle progression in mammalian cells. However, little is known about Ran function in rice (Oryza sativa). Plant Ran GTPase may have an important and conserved role in cold stress signalling in plants.
- 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). Near chromosomes, RCC1 generates Ran–GTP that in turn regulates microtubule dynamics. At kinetochores and on spindles, RanGAP mediates Ran–GTP hydrolysis.
- 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 .
- 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 and the assembly of the mitotic spindle and nuclear envelope (NE). 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.
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
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