title: Expression analysis and functional characterization of the monosaccharide transporters, OsTMTs, involving vacuolar sugar transport in rice (Oryza sativa).
abstract: In Arabidopsis, the compartmentation of sugars into vacuoles is known to be facilitated by sugar transporters. However, vacuolar sugar transporters have not been studied in detail in other plant species. To characterize the rice (Oryza sativa) tonoplast monosaccharide transporters, OsTMT1 and OsTMT2, we analysed their subcellular localization using green fluorescent protein (GFP) and expression patterns using reverse-transcription polymerase chain reaction (RT-PCR), performed histochemical beta-glucuronidase (GUS) assay and in situ hybridization analysis, and assessed sugar transport ability using isolated vacuoles. Expression of OsTMT-GFP fusion protein in rice and Arabidopsis revealed that the OsTMTs localize at the tonoplast. Analyses of OsTMT promoter-GUS transgenic rice indicated that OsTMT1 and OsTMT2 are highly expressed in bundle sheath cells, and in vascular parenchyma and companion cells in leaves, respectively. Both genes were found to be preferentially expressed in the vascular tissues of roots, the palea/lemma of spikelets, and in the main vascular tissues and nucellar projections on the dorsal side of the seed coats. Glucose uptake studies using vacuoles isolated from transgenic mutant Arabidopsis (tmt1-2-3) expressing OsTMT1 demonstrated that OsTMTs are capable of transporting glucose into vacuoles. Based on expression analysis and functional characterization, our present findings suggest that the OsTMTs play a role in vacuolar glucose storage in rice.
authors.affiliation: Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Jung-Il
authors.initials: JI
authors.lastname: Cho
authors.forename: Bo
authors.initials: B
authors.lastname: Burla
authors.forename: Dae-Woo
authors.initials: DW
authors.lastname: Lee
authors.forename: Nayeon
authors.initials: N
authors.lastname: Ryoo
authors.forename: Soon-Kwan
authors.initials: SK
authors.lastname: Hong
authors.forename: Hyun-Bi
authors.initials: HB
authors.lastname: Kim
authors.forename: Joon-Seob
authors.initials: JS
authors.lastname: Eom
authors.forename: Sang-Bong
authors.initials: SB
authors.lastname: Choi
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
authors.forename: Seong Hee
authors.initials: SH
authors.lastname: Bhoo
authors.forename: Tae-Ryong
authors.initials: TR
authors.lastname: Hahn
authors.forename: H Ekkehard
authors.initials: HE
authors.lastname: Neuhaus
authors.forename: Enrico
authors.initials: E
authors.lastname: Martinoia
authors.forename: Jong-Seong
authors.initials: JS
authors.lastname: Jeon
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D005947:Glucose / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012275:Oryza / Q000166:cytology / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D005966:Glucuronidase; D005947:Glucose