Os02g0274900

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The rice OsGMST1 gene is a novel Golgi-localized monosaccharide transporter that may play a role in salt stress tolerance.[1]

Annotated Information

Function

OsGMST1 is a member of the monosaccharide transporter family in rice. It encodes a putative monosaccharide transporter.[1]
Monosaccharide transporters play a pivotal role in the translocation and distribution of monosaccharides throughout the plant.The mobility of sugars between source and sink tissues in plants depends on sugar transport proteins.[1][2] Hong Cao et al.speculates that this gene is a sugar transporter based on its sequence characteristics and the effect on the sugar content when the gene expression is reduced in rice.It is hypothesized that sugar homeostasis is affected in OsGMST1 knockdown transgenic rice, which putatively results in altered sugar contents, so the seedlings show a NaCl hypersensitive phenotype.

GO assignment(s): GO:0005215, GO:0005351, GO:0006810, GO:0008643, GO:0016020, GO:0016021

Mutation

Figure 1.Salt tolerance test of OsGMST1 antisense transgenic rice plants (from reference [1]).
  • There were no differences in the seed germination rate between WT and the transgenic lines without NaCl stress(Figure 1A). Treatment with 150 mM and 200 mM NaCl,however, reduced the germination rate of AS-L12 and ASL18(Figure 1A, B).
  • At 200 mM NaCl, the germination rate of the wild type was 90%, while the germination rates of the AS-L12 and AS-L18 lines were reduced to 40% and 50%,respectively (P <0.01) (Figure 1B), and this difference was maintained over several days (P <0.01) (Figure 1C).
  • Reduced expression of OsGMST1 also conferredreduced tolerance to salt stress in young seedlings(Figure 1D).
  • The survival rate of AS-L12 (40% and 20% in 150 mM NaCl and 200 mM NaCl, respectively) and ASL18 (50% and 30%) were lower than the WT (70% and 50%)with treatment of 150 mM and 200 mM NaCl (P <0.01)(Figure 1E).
  • By contrast, the tolerance of OsGMST1 antisense plants to PEG and cold stress was the same as that of WT plants (Figure 1F, G). Just as for SGB1, increased expression of OsGMST1 had no effect.

Expression

Figure 2. Expression analyses of OsGMST1(from reference [1]).

OsGMST1 expression is induced by salt treatment and reduced expression confers hypersensitivity to salt stress in rice.[1]

  • Transgenic rice plants expressing b-glucoronidase gene driven by the OsGMST1 promoter showed that OsGMST2 was expressed in all developmental stages from germination to flowering(Figure 2A).
  • Quantitative PCR confirmed high levels of OsGMST1 mRNA in all the organs tested, such as the shoot, root, culm, panicle, leaf, and leaf sheath before and after heading (Figure 2B), suggesting that OsGMST1 is ubiquitously expressed.
  • OsGMST1 is expressed ubiquitously (Figure 2A and B),suggesting that it may be involved in sugar translocation in both source and sink tissues of rice.
  • The transcript level of OsGMST1 in seedlings was induced by NaCl treatment but unaffected by low temperature and PEG4000. Salt treatment conferred a sustained increase in the steady-state level of the OsGMST1 mRNA.(Figure 2C)NaCl stress up-regulates the expression of OsGMST1 transcriptionally(Figure 2C)One possible explanation is that NaCl stress stimulates the monosaccharide transport activity of OsGMST1 and, consequently, the activated OsGMST1 upon salt stress import sugars into the Golgi or export them out of the organelle to keep cytosolic sugar at homeostasis.

Subcellular localization

  • OsGMST1-GFP was co-expressed with the Golgi marker sialyltransferase (ST) tagged red fluorescence protein (RFP), most of the red and green fluorescence merged. The analysis by Hong Cao et al. suggests that OsGMST1 is localized on the Golgi apparatus [1].

Homologues

Figure 3. Phylogenic analysis of OsGMST1 homologues from rice and other organisms by MEGA 4.0.(from reference) [1].

Phylogenetic analysis (Fig. 1B) shows that the putative Arabidopsis paralogues to OsGMST1 are encoded by At1g67300, SGB1, At1g05030, and AtpGlcT and the proteins have 67%, 65%, 44%, and 43% identity to OsGMST1,respectively.These four MST proteins are in the pGlcT subfamily. SGB1 Encodes a Putative Hexose Transporter.[3] In rice(Japonica), OsGMST1, Os09g23110, and Os01g04190(OspGlcT) belong to the pGlcT subfamily with sequence identity approximately 36%.SGB1 is shown here to be a Golgi-localized hexose transporter and acts genetically with AGB1 in early seedling development.[1][3].

Knowledge Extension

Sugars are signalling molecules that regulate plant growth and development and responses to biotic and abiotic stresses.In plants carbohydrates are used as a universal energy currency,different sugar signals are generated by photosynthesis and carbon metabolism in source and sink tissues to modulate growth, development,and stress responses.[2][4] Sugars, have acquired important regulatory functions early in evolution, controlling metabolism, stress resistance, growth,and development in bacteria, yeasts, plants,and animals. The regulatory roles of sugars are most explicit in free-living microorganisms that are challenged by a constantly, often dramatically changing environment.[4]
Carbohydrate allocation to long distance, at the level of the plant, as well as to short distance, in sugar partitioning at cellular level, requires sugar transporters. They are membrane proteins belonging to the major facilitator superfamily (MFS) whose subfamilies of sucrose transporters (SUTs) and monosaccharide transporters (MSTs) are the most studied.[5]SUCs and MSTs are the main sugar transporters in plants.Some MSTs may play a pivotal role during stress responses.In rice, the expression of the Golgi monosaccharidetransporter OsGMST1 is positively correlated to salt treatment.[1][5]

Labs working on this gene

  • Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
  • Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
  • Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
  • National Research Center for Plant Gene, Beijing 100093, China

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Cao H, Guo S, Xu Y, et al. Reduced expression of a gene encoding a Golgi localized monosaccharide transporter (OsGMST1) confers hypersensitivity to salt in rice (Oryza sativa)[J]. Journal of experimental botany, 2011: err178.
  2. 2.0 2.1 Reuscher S, Akiyama M, Yasuda T, et al. The Sugar Transporter Inventory Of Tomato: Genome-Wide Identification And Expression Analysis[J]. Plant and Cell Physiology, 2014: pcu052.
  3. 3.0 3.1 Wang H X, Weerasinghe R R, Perdue T D, et al. A Golgi-localized hexose transporter is involved in heterotrimeric G protein-mediated early development in Arabidopsis[J]. Molecular biology of the cell, 2006, 17(10): 4257-4269.
  4. 4.0 4.1 Rolland F, Baena-Gonzalez E, Sheen J. Sugar sensing and signaling in plants: conserved and novel mechanisms[J]. Annu. Rev. Plant Biol., 2006, 57: 675-709.
  5. 5.0 5.1 Medici A, Laloi M, Atanassova R. Profiling of sugar transporter genes in grapevine coping with water deficit[J]. FEBS letters, 2014, 588(21): 3989-3997.


Structured Information