title: Impaired function of the tonoplast-localized sucrose transporter in rice, OsSUT2, limits the transport of vacuolar reserve sucrose and affects plant growth.
abstract: Physiological functions of sucrose (Suc) transporters (SUTs) localized to the tonoplast in higher plants are poorly understood. We here report the isolation and characterization of a mutation in the rice (Oryza sativa) OsSUT2 gene. Expression of OsSUT2-green fluorescent protein in rice revealed that OsSUT2 localizes to the tonoplast. Analysis of the OsSUT2 promoter::β-glucuronidase transgenic rice indicated that this gene is highly expressed in leaf mesophyll cells, emerging lateral roots, pedicels of fertilized spikelets, and cross cell layers of seed coats. Results of Suc transport assays in yeast were consistent with a H(+)-Suc symport mechanism, suggesting that OsSUT2 functions in Suc uptake from the vacuole. The ossut2 mutant exhibited a growth retardation phenotype with a significant reduction in tiller number, plant height, 1,000-grain weight, and root dry weight compared with the controls, the wild type, and complemented transgenic lines. Analysis of primary carbon metabolites revealed that ossut2 accumulated more Suc, glucose, and fructose in the leaves than the controls. Further sugar export analysis of detached leaves indicated that ossut2 had a significantly decreased sugar export ability compared with the controls. These results suggest that OsSUT2 is involved in Suc transport across the tonoplast from the vacuole lumen to the cytosol in rice, playing an essential role in sugar export from the source leaves to sink organs.
authors.affiliation: Graduate School of Biotechnology and Plant Metabolism Research Center, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Joon-Seob
authors.initials: JS
authors.lastname: Eom
authors.forename: Jung-Il
authors.initials: JI
authors.lastname: Cho
authors.forename: Anke
authors.initials: A
authors.lastname: Reinders
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Youngchul
authors.initials: Y
authors.lastname: Yoo
authors.forename: Pham Quoc
authors.initials: PQ
authors.lastname: Tuan
authors.forename: Sang-Bong
authors.initials: SB
authors.lastname: Choi
authors.forename: Geul
authors.initials: G
authors.lastname: Bang
authors.forename: Youn-Il
authors.initials: YI
authors.lastname: Park
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
authors.forename: Seong Hee
authors.initials: SH
authors.lastname: Bhoo
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
authors.forename: Tae-Ryong
authors.initials: TR
authors.lastname: Hahn
authors.forename: John M
authors.initials: JM
authors.lastname: Ward
authors.forename: Jong-Seong
authors.initials: JS
authors.lastname: Jeon
mesh_terms: D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D015388:Organelles / Q000378:metabolism*; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D010940:Plant Proteins; D013395:Sucrose