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1、ThePlantCell,Vol.22:2045–2057,June2010,www.plantcell.orgã2010AmericanSocietyofPlantBiologistsAVacuolarArseniteTransporterNecessaryforArsenicToleranceintheArsenicHyperaccumulatingFernPterisvittataIsMissinginFloweringPlantsWOAEmilyIndriolo,aGunNamNa,bDanielleEllis,c
2、DavidE.Salt,d,1andJoAnnBanksbaDepartmentofCellandSystemsBiology,UniversityofToronto,Toronto,CanadaM5S3B2bDepartmentofBotanyandPlantPathology,PurdueUniversity,WestLafayette,Indiana47906cBiologyDepartment,WestVirginiaUniversity,Morgantown,WestVirginia26506dDepartmen
3、tofHorticultureandLandscapeArchitecture,PurdueUniversity,WestLafayette,Indiana47906ThefernPterisvittatatoleratesandhyperaccumulatesexceptionallyhighlevelsofthetoxicmetalloidarsenic,andthistraitappearsuniquetothePteridaceae.Oncetakenupbytheroot,arsenateisreducedtoa
4、rseniteasitistransportedtothelaminaofthefrond,whereitisstoredincellsasfreearsenite.Here,wedescribetheisolationandcharacterizationoftwoP.vittatagenes,ACR3andACR3;1,whichencodeproteinssimilartotheACR3arseniteeffluxerofyeast.PvACR3isabletorescuethearsenic-sensitivephe
5、notypesofyeastdeficientforACR3.ACR3transcriptsareupregulatedbyarsenicinsporophyterootsandgametophytes,tissuesthatdirectlycontactsoil,whereasACR3;1expressionisunaffectedbyarsenic.KnockingdowntheexpressionofACR3,butnotACR3;1,inthegametophyteresultsinanarsenite-sensit
6、ivephenotype,indicatingthatACR3playsanecessaryroleinarsenictoleranceinthegametophyte.WeshowthatACR3localizestothevacuolarmembraneingametophytes,indicatingthatitlikelyeffluxesarseniteintothevacuoleforsequestration.Whereassingle-copyACR3genesarepresentinmoss,lycophyt
7、es,otherferns,andgymnosperms,nonearepresentinangiosperms.TheduplicationofACR3inP.vittataandthelossofACR3inangiospermsmayexplainarsenictoleranceinthisunusualgroupoffernswhileprecludingthesametraitinangiosperms.INTRODUCTIONaccumulatehighlevelsofarsenic,P.vittataisan
8、excellentsystemforstudyingthemechanismsresponsibleforarsenicArsenicisanaturallyoccurringmetalloidthatistoxictomostmetabolism,toxicity,andresistanceinamu
