title: Genome-wide annotation and functional identification of aphid GLUT-like sugar transporters.
abstract: BACKGROUND
  Phloem feeding insects, such as aphids, feed almost continuously on plant phloem sap, a liquid diet that contains high concentrations of sucrose (a disaccharide comprising of glucose and fructose). To access the available carbon, aphids hydrolyze sucrose in the gut lumen and transport its constituent monosaccharides, glucose and fructose. Although sugar transport plays a critical role in aphid nutrition, the molecular basis of sugar transport in aphids, and more generally across all insects, remains poorly characterized. Here, using the latest release of the pea aphid, Acyrthosiphon pisum, genome we provide an updated gene annotation and expression profile of putative sugar transporters. Finally, gut expressed sugar transporters are functionally expressed in yeast and screened for glucose and fructose transport activity.
  
  
  RESULTS
  In this study, using a de novo approach, we identified 19 sugar porter (SP) family transporters in the A. pisum genome. Gene expression analysis, based on 214, 834 A. pisum expressed sequence tags, supports 17 sugar porter family transporters being actively expressed in adult female aphids. Further analysis, using quantitative PCR identifies 4 transporters, A. pisum sugar transporter 1, 3, 4 and 9 (ApST1, ApST3, ApST4 and ApST9) as highly expressed and/or enriched in gut tissue. When expressed in a Saccharomyces cerevisiae hexose transporter deletion mutant (strain EBY.VW4000), only ApST3 (previously characterized) and ApST4 (reported here) transport glucose and fructose resulting in functional rescue of the yeast mutant. Here we characterize ApST4, a 491 amino acid protein, with 12 predicted transmembrane regions, as a facilitative glucose/fructose transporter. Finally, phylogenetic reconstruction reveals that ApST4, and related, as yet uncharacterized insect transporters are phylogenetically closely related to human GLUT (SLC2A) class I facilitative glucose/fructose transporters.
  
  
  CONCLUSIONS
  The gut enhanced expression of ApST4, and the transport specificity of its product is consistent with ApST4 functioning as a gut glucose/fructose transporter. Here, we hypothesize that both ApST3 (reported previously) and ApST4 (reported here) function at the gut interface to import glucose and fructose from the gut lumen.
authors.affiliation: School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. danrgp@gmail.com.
authors.forename: Daniel R G
authors.initials: DR
authors.lastname: Price
authors.forename: John A
authors.initials: JA
authors.lastname: Gatehouse
mesh_terms: D000818:Animals; D001042:Aphids / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D020224:Expressed Sequence Tags / Q000378:metabolism; D005260:Female; D005632:Fructose / Q000378:metabolism; D023281:Genomics; D005947:Glucose / Q000378:metabolism; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D019476:Insect Proteins / Q000235:genetics* / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D008297:Male; D058977:Molecular Sequence Annotation; D010802:Phylogeny
chemical_list: D051246:Glucose Transport Proteins, Facilitative; D019476:Insect Proteins; D005632:Fructose; D005947:Glucose
references.citation: Am J Physiol Endocrinol Metab. 2010 Feb;298(2):E141-5
references.pmid: 20009031
references.citation: J Exp Biol. 1999 Oct;202 (Pt 19):2639-52
references.pmid: 10482723
references.citation: Nat Protoc. 2007;2(1):35-7
references.pmid: 17401335
references.citation: Mol Aspects Med. 2013 Apr-Jun;34(2-3):121-38
references.pmid: 23506862
references.citation: Insect Biochem Mol Biol. 2010 Nov;40(11):805-13
references.pmid: 20705135
references.citation: Mol Biol Evol. 2011 Nov;28(11):3113-26
references.pmid: 21613235
references.citation: Biochemistry. 1998 Feb 3;37(5):1322-6
references.pmid: 9477959
references.citation: Mol Microbiol. 2000 Feb;35(4):699-710
references.pmid: 10692148
references.citation: FEBS J. 2012 Jun;279(11):2022-35
references.pmid: 22458847
references.citation: Nucleic Acids Res. 2004 Mar 19;32(5):1792-7
references.pmid: 15034147
references.citation: Trends Biochem Sci. 1993 Jan;18(1):13-20
references.pmid: 8438231
references.citation: J Insect Physiol. 2003 Jan;49(1):11-24
references.pmid: 12770012
references.citation: Nucleic Acids Res. 2014 Jan;42(Database issue):D897-902
references.pmid: 24275491
references.citation: Nucleic Acids Res. 2001 Jan 1;29(1):41-3
references.pmid: 11125044
references.citation: Insect Biochem Mol Biol. 2007 Apr;37(4):307-17
references.pmid: 17368194
references.citation: Biochemistry. 1996 Dec 24;35(51):16519-27
references.pmid: 8987985
references.citation: J Mol Biol. 1982 May 5;157(1):105-32
references.pmid: 7108955
references.citation: J Biol Chem. 1991 Oct 25;266(30):19867-70
references.pmid: 1939050
references.citation: Insect Mol Biol. 2010 Mar;19 Suppl 2:97-112
references.pmid: 20482643
references.citation: Appl Environ Microbiol. 2003 Aug;69(8):4403-7
references.pmid: 12902222
references.citation: J Mol Biol. 1999 Dec 17;294(5):1351-62
references.pmid: 10600390
references.citation: Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):320-5
references.pmid: 24367072
references.citation: Mol Biol Evol. 2011 Oct;28(10):2731-9
references.pmid: 21546353
references.citation: Physiol Rev. 2011 Apr;91(2):733-94
references.pmid: 21527736
references.citation: Insect Mol Biol. 2010 Mar;19 Suppl 2:23-31
references.pmid: 20482637
references.citation: Insect Biochem Mol Biol. 2007 Nov;37(11):1138-48
references.pmid: 17916500
references.citation: Bioinformatics. 1998;14(9):755-63
references.pmid: 9918945
references.citation: Physiology (Bethesda). 2007 Aug;22:234-40
references.pmid: 17699876
references.citation: J Mol Biol. 2001 Jan 19;305(3):567-80
references.pmid: 11152613
references.citation: Bioinformatics. 2009 Aug 1;25(15):1972-3
references.pmid: 19505945
references.citation: Methods. 2001 Dec;25(4):402-8
references.pmid: 11846609
references.citation: BMC Genomics. 2008 Mar 03;9:117
references.pmid: 18315884
references.citation: FEBS Lett. 1999 Dec 31;464(3):123-8
references.pmid: 10618490
references.citation: PLoS Biol. 2010 Feb 23;8(2):e1000313
references.pmid: 20186266
references.citation: J Exp Biol. 1996;199(Pt 6):1269-76
references.pmid: 9319135
references.citation: Microbiol Mol Biol Rev. 2000 Jun;64(2):354-411
references.pmid: 10839820
references.citation: J Insect Physiol. 2000 Mar;46(3):335-341
references.pmid: 12770238