title: SWEETs, transporters for intracellular and intercellular sugar translocation.
abstract: Three families of transporters have been identified as key players in intercellular transport of sugars: MSTs (monosaccharide transporters), SUTs (sucrose transporters) and SWEETs (hexose and sucrose transporters). MSTs and SUTs fall into the major facilitator superfamily; SWEETs constitute a structurally different class of transporters with only seven transmembrane spanning domains. The predicted topology of SWEETs is supported by crystal structures of bacterial homologs (SemiSWEETs). On average, angiosperm genomes contain ∼20 paralogs, most of which serve distinct physiological roles. In Arabidopsis, AtSWEET8 and 13 feed the pollen; SWEET11 and 12 provide sucrose to the SUTs for phloem loading; AtSWEET11, 12 and 15 have distinct roles in seed filling; AtSWEET16 and 17 are vacuolar hexose transporters; and SWEET9 is essential for nectar secretion. The remaining family members await characterization, and could play roles in the gametophyte as well as other important roles in sugar transport in the plant. In rice and cassava, and possibly other systems, sucrose transporting SWEETs play central roles in pathogen resistance. Notably, the human genome also contains a glucose transporting isoform. Further analysis promises new insights into mechanism and regulation of assimilate allocation and a new potential for increasing crop yield.
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA.
authors.forename: Joon-Seob
authors.initials: JS
authors.lastname: Eom
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA.
authors.forename: Li-Qing
authors.initials: LQ
authors.lastname: Chen
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA.
authors.forename: Davide
authors.initials: D
authors.lastname: Sosso
authors.affiliation: Division of Biological Sciences, Interdisciplinary Plant Group, and the Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO 65211, USA.
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Julius
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA; Biology Department, Stanford University, Stanford, CA 94305, USA.
authors.forename: I W
authors.initials: IW
authors.lastname: Lin
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Qu
authors.affiliation: Division of Biological Sciences, Interdisciplinary Plant Group, and the Missouri Maize Center, University of Missouri, 110 Tucker Hall, Columbia, MO 65211, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Braun
authors.affiliation: Carnegie Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA; Biology Department, Stanford University, Stanford, CA 94305, USA. Electronic address: wfrommer@carnegiescience.edu.
authors.forename: Wolf B
authors.initials: WB
authors.lastname: Frommer
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D050260:Carbohydrate Metabolism; D002241:Carbohydrates; D003593:Cytoplasm / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*
chemical_list: D002241:Carbohydrates; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins; C078729:sucrose transport protein, plant