title: STP10 encodes a high-affinity monosaccharide transporter and is induced under low-glucose conditions in pollen tubes of Arabidopsis.
abstract: Pollen tubes are fast growing, photosynthetically inactive cells. Their energy demand is covered by specific transport proteins in the plasma membrane that mediate the uptake of sugars. Here we report on the functional characterization of AtSTP10, a previously uncharacterized member of the SUGAR TRANSPORT PROTEIN family. Heterologous expression of STP10 cDNA in yeast revealed that the encoded protein catalyses the high-affinity uptake of glucose, galactose and mannose. The transporter is sensitive to uncouplers of transmembrane proton gradients, indicating that the protein acts as a hexose-H(+)symporter. Analyses of STP10 mRNA and STP10 promoter-reporter gene studies revealed a sink-specific expression pattern of STP10 in primordia of lateral roots and in pollen tubes. This restriction to sink organs is mediated by intragenic regions of STP10 qPCR analyses with cDNA of in vitro grown pollen tubes showed that STP10 expression was down-regulated in the presence of 50mM glucose. However, in pollen tubes of glucose-insensitive plants, which lack the glucose sensor hexokinase1 (HXK1), no glucose-induced down-regulation of STP10 expression was detected. A stp10T-DNA insertion line developed normally, which may point towards functional redundancy. The data presented in this paper indicate that a high-affinity glucose uptake system is induced in growing pollen tubes under low glucose conditions and that this regulation may occur through the hexokinase pathway.
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Theresa
authors.initials: T
authors.lastname: Rottmann
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Zierer
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Christa
authors.initials: C
authors.lastname: Subert
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nürnberg, 91058 Erlangen, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Sauer
authors.affiliation: Molecular Plant Physiology, University Erlangen-Nürnberg, 91058 Erlangen, Germany ruth.stadler@fau.de.
authors.forename: Ruth
authors.initials: R
authors.lastname: Stadler
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017930:Genes, Reporter; D005947:Glucose / Q000494:pharmacology*; D005966:Glucuronidase / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional / Q000235:genetics; D053205:Pollen Tube / Q000187:drug effects / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D020539:Sequence Analysis, Protein; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C103791:STP4 protein, Arabidopsis; C036483:T-DNA; D005966:Glucuronidase; D005947:Glucose
keywords: Arabidopsis; STP10; Saccharomyces cerevisiae; gene expression regulation; glucose; hexokinase; monosaccharides; pollen tubes; radioactive uptake measurement; sugar signalling; sugar transport.