title: Role of the plastidic glucose translocator in the export of starch degradation products from the chloroplasts in Arabidopsis thaliana.
abstract: In higher plants, the plastidic glucose translocator (pGlcT) is assumed to play a role in the export of starch degradation products, but this has not yet been studied in detail. To elucidate the role of pGlcT in the leaves of Arabidopsis thaliana, we generated single and double mutants lacking three plastidic sugar transporters, pGlcT, the triose-phosphate/phosphate translocator (TPT), and the maltose transporter (MEX1), and analyzed their growth phenotypes, photosynthetic properties and metabolite contents. In contrast to the pglct-1 and pglct-2 single mutants lacking a visible growth phenotype, the double mutants pglct-1/mex1 and tpt-2/mex1 displayed markedly inhibited plant growth. Notably, pglct-1/mex1 exhibited more severe growth retardation than that seen for the other mutants. In parallel, the most severe reductions in sucrose content and starch turnover were observed in the pglct-1/mex1 mutant. The concurrent loss of pGlcT and MEX1 also resulted in severely reduced photosynthetic activities and extreme chloroplast abnormalities. These findings suggest that pGlcT, together with MEX1, contributes significantly to the export of starch degradation products from chloroplasts in A. thaliana leaves, and that this starch-mediated pathway for photoassimilate export via pGlcT and MEX1 is essential for the growth and development of A. thaliana.
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Man-Ho
authors.initials: MH
authors.lastname: Cho
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Hyemin
authors.initials: H
authors.lastname: Lim
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Shin
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Jong-Seong
authors.initials: JS
authors.lastname: Jeon
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Seong Hee
authors.initials: SH
authors.lastname: Bhoo
authors.affiliation: Department of Biological Science and Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon 305-764, Korea.
authors.forename: Youn-Il
authors.initials: YI
authors.lastname: Park
authors.affiliation: Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Tae-Ryong
authors.initials: TR
authors.lastname: Hahn
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D002940:Circadian Rhythm; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010788:Photosynthesis; D012098:Reproduction; D012995:Solubility; D013213:Starch / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D051246:Glucose Transport Proteins, Facilitative; C000590716:MEX1 protein, Arabidopsis; D026901:Membrane Transport Proteins; C000594041:pGLCT protein, Arabidopsis; D013213:Starch; D005947:Glucose