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more authorsAbstractLipid and fatty acid analyses were performed on whole leaf extracts and isolated thylakoids from winter rye (Secale cereale L. cv Puma) grown at 5 degrees C cold-hardened rye (RH) and 20 degrees C nonhardened rye (RNH). Although no significant change in total lipid content was observed, growth at low, cold-hardening temperature resulted in a specific 67% (thylakoids) to 74% (whole leaves) decrease in the trans-Delta(3)-hexadecenoic acid (trans-16:1) level associated with phosphatidyldiacylglycerol (PG). Electron spin resonance and differential scanning calorimetry (DSC) indicated no significant difference in the fluidity of RH and RNH thylakoids. Separation of chlorophyll-protein complexes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the ratio of oligomeric light harvesting complex:monomeric light harvesting complex (LHCII(1):LHCII(3)) was 2-fold higher in RNH than RH thylakoids. The ratio of CP1a:CP1 was also 1.5-fold higher in RNH than RH thylakoids. Analyses of winter rye grown at 20, 15, 10, and 5 degrees C indicated that both, the trans-16:1 acid levels in PG and the LHCII(1):LHCII(3) decreased concomitantly with a decrease in growth temperature. Above 40 degrees C, differential scanning calorimetry of RNH thylakoids indicated the presence of five major endotherms (47, 60, 67, 73, and 86 degrees C). Although the general features of the temperature transitions observed above 40 degrees C in RH thylakoids were similar to those observed for RNH thylakoids, the transitions at 60 and 73 degrees C were resolved as inflections only and RH thylakoids exhibited transitions at 45 and 84 degrees C which were 2 degrees C lower than those observed in RNH thylakoids. Since polypeptide and lipid compositions of RH and RNH thylakoids were very similar, we suggest that these differences reflect alterations in thylakoid membrane organization. Specifically, it is suggested that low developmental temperature modulates LHCII organization such that oligomeric LHCII predominates in RNH thylakoids whereas a monomeric or an intermediate form of LHCII predominates in RH thylakoids. Furthermore, we conclude that low developmental temperature modulates LHCII organization by specifically altering the fatty composition of thylakoid PG.Discover the world's research11+ million members100+ million publications100k+ research projects
PlantPhysiol.(1987)84,12-18/84/.00/0LowTemperatureDevelopmentInducesaSpecificDecreaseintrans-A3-HexadecenoicAcidContentwhichInfluencesLHCIIOrganization1ReceivedforpublicationJuly2,1986andinrevisedformDecember1,1986NORMANP.A.HUNER*,MARIANNAKROL,JOHNP.WILLIAMS,ELLENMAISSAN,PHILLIPS.Low,DANEROBERTS,ANDJOHNE.THOMPSONDepartmentofPlantSciences,UniversityofWesternOntario,London,Ontario,CanadaN6A5B7(N.P.A.H.,M.K.);BotanyDepartment,UniversityofToronto,Toronto,CanadaM5SJA](J.P.W.,E.M.);ChemistryDepartment,PurdueUniversity,WestLafayette,Indiana47907(P.S.L.);andBiologyDepartment,UniversityofWaterloo,Waterloo,CanadaN2L3GJ(D.R.,J.E.T.)ABSTRACTLipidandfattyacidanalyseswereperfornmedonwholeleafextractsandisolatedthylakoidsfromwinterrye(SecalkcereakL.cvPunia)grownat5°Ccold-hardenedrye(RH)and20°Cnonhardenedrye(RNH).Althoughnosignificantcgeintotallipidcontentwasobserved,growthatlow,cold-hardeningtemperatureresultedinaspecific67%(thylakoids)to74%(wholeleaves)decreaseinthetrans-A3-hexadecenoicacid(trans-16:1)levelassociatedwithphosphatidyldiacylglycerol(PG).Electronspinresonanceanddifferentialscanningcalorimetry(DSC)indicatednosignificantdifferenceinthefluidityofRHandRNHthylakoids.Sepa-rationofchlorophyll-proteincomplexesbysodiumdodecylsulfate-poly-acrylamidegelelectrophoresisindicatedthattheratioofoligomericlightharvestingcomplex:monomericlightharvestingcomplex(LHCII,:LHCII3)was2-foldhigherinRNHthanRHthylakoids.TheratioofCP1a:CP1wasalso1.5-foldhigherinRNHthanRHthylakoids.Analysesofwinterryegrownat20,15,10,and5Cindicatedthatboth,thetras-16:1acidlevelsinPGandtheLHCII,:LHCII3decreasedconcomitantlywithadecreaseingrowthtemperature.Above40C,differentialscanningcalorimetryofRNHthylakoidsindicatedthepres-enceoffivemajorendotherms(47,60,67,73,and86C).Althoughthegeneralfeaturesofthetemperaturetransitionsobservedabove40°CinRHthylakoidsweresimilartothoseobservedforRNHthylakoids,thetransitionsat60and73°CwereresolvedasinflectionsonlyandRHthylakoidsexhibitedtrasitionsat45and84°Cwhichwere2°ClowerthanthoseobservedinRNHthylakoids.SincepolypeptideandlipidcompositionsofRHandRNHthylakoidswereverysimilar,wesuggestthatthesedifferencesreflectalterationsinthylakoidmembraneorgani-zation.Specifically,itissuggestedthatlowdevelopmentaltemperaturemodulatesLHCIIorganizationsuchthatoligomericLHCHIpredominatesinRNHthylakoidswhereasamonomericoranintermediateformofLHCIIpredominatesinRHthylakoids.Furthermore,weconcludethatlowdevelopmentaltemperaturemodulatesLHCHorganizationbyspe-cificallyalteringthefattycompositionofthylakoidPG.Recently,Griffith,etal.(13)reportedthatChlbofthylakoidmembranesisolatedfromwinterryegrownatlow,cold-harden-&SupportedbytheNaturalSciencesandEngineeringResearchCoun-cilofCanada.12ingtemperatures(5C)(RH)2exhibitedadifferentialextractabil-itytothenonionicdetergents,TritonX-100and-,-octylgluco-side,comparedtoChlbofryethylakoidsdevelopedatwarmtemperatures(20C)(RNH).AutoradiogramsofRHandRNHthylakoidsextractedwithSDSindicatedthattheLHCIIpolypep-tideswerephosphorylatedinvitrotothesameextentbyalight-dependentthylakoidproteinkinase.However,solubilizationoflabeledRHandRNHthylakoidswithB-octylglucosideandsubsequentelectrophoresisindicatedthatminimalamountsoflabeledLHCIIcouldbeextractedfromRHthylakoidscomparedtothecopiousamountsoflabeledLHCIIextractedfromRNHthylakoids.LabeledRHLHCIIpolypeptideswerereportedtobeassociatedwithanonpigmentedproteincomplexwithamolec-ularmassgreaterthanthatofCPluponsolubilizationofRHthylakoidswith,3-octylglucoside.Griffithelal.(13)concludedthatgrowthanddevelopmentofwinterryeatlowtemperatureresultsinanalterationinprotein-proteininteractionsassociatedwithLHCII.ThisisconsistentwithpreviousreportswhichindicatedthatRHthylakoidsexhibitedadecreaseinparticlesizeontheEFfractureface(17),anincreaseintheF685/F742butdidnotexhibitaconcomitantincreaseinPSIIactivityattheexpenseofPSIactivitynoranydetectablechangeinphotosyntheticunitsize(11,15-17).However,Huneretal.(10,17)havealsoreportedthatnosignificantdifferencesbetweenRHandRNHthylakoidsexistwithrespecttopigmentorpolypeptidecompo-sition.Inthisreport,weexaminethelipidandfattyacidcom-positionsofRHandRNHthylakoidsinordertodetermineiftheobservedchangesinthestructureandfunctionofRHLHCII2Abbreviations:RH,cold-hardenedRNH,nonhardenedrye:LHCII,lightharvestingChla/bproteinassociatedwithphotosystemII;LHCII,,oligomericformofLHCII;LHCII2,dimericformofLHCII;LHCII3,monomericformofLHCII;CPla,oligomericformofCPI;CPI,Chla-proteincomplexassociatedwiththereactioncenterofphotosystemI;CPa,Chla-proteincomplexassociatedwiththereactioncenterforPSII;FP,freeF6g5,77&KChlafluorescenceemissionmaximumat685F742,77°KChlafluorescenceemissionmaximumat742DOC,DPH,1,6-diphenyl-1,3,5-PC,PE,phosSL,sulfoqui-nPG,phosphMGDG,mono-galactosyldiacylDGDG,digalactosyldiacyltrans-16:1,trans-A3-hexadecenoic16:0,palmitic18:3,linolenicDSC,differentialscanningDCMU,343,4-dichlorophenyl)-1,1dimethylEF,exoplasmicfracture1(1,14),16-dox-ylstearicacid.
LOWTEMPERATUREDEVELOPMENTANDtrans-A3-HEXADECENOICACIDarerelatedtoalterationsinthylakoidlipidcompositionandcontent.MATERIALSANDMETHODSPlantMaterials.Winterrye(SecalecerealeL.cvPuma)wasgrowninvermiculitewateredwithHoaglandnutrientsolution.Seedlingswereinitiallygrownincontrolledenvironmentgrowthchambersata20°C/16°C(day/night)temperatureregimeanda16hphotoperiodwithalightintensityof200Mmolphotonsm2s-&(PAR)for7d.Afterthistime,theprimaryleafhadfullyexpandedwhereasthesecondleafhadonlypartiallyexpanded(18).Seedlings(7-d-old)werethenshiftedforanadditional7to8weekstoatemperatureregimeof5°C/5°C(day/night)withallotherconditionskeptconstant.TheseplantsarereferredtoasRH.Controlseedlingsremainedatthe20°Ctemperatureregimeforanadditional2.5to3weeks.TheseplantsarereferredtoasRNH.Kroletal.(18)haveshownthatRHandRNHplantswereofcomparablephysiologicalagewhengrownundertheseconditions.IsolationofThylakoidMembranes.Uppermost,fullyex-pandedleavesofRHandRNHplantsweremaceratedat4°Cand50mmTricine(pH7.8)containing0.4Msorbitoland10mMNaClwithtwo5sburstsofaWaringBlendor.ThebreiwasfilteredthroughtwolayersofMiraclothandthefiltratewassubsequentlycentrifugedat3000gfor5min.Thepelletwaswashedin50mMTricine(pH7.8)containing10mMNaCland5mMMgCl2andsubsequentlyresuspendedin50mMTricine(pH7.8)containing0.1Msorbitol,10mmNaCl,and5mMMgCI2andkeptoniceinthedark.LipidandFattyAcidAnalyses.UppermostfullyexpandedleavesofRHandRNHplantsaswellasisolatedRHandRNHthylakoidswereextractedandanalyzedfortheirlipidandfattyacidcompositionsaspreviouslydescribed(27,28).SeparationofChlorophyll-ProteinComplexes.Thylakoidmembraneswereisolatedasdescribedaboveexceptthattheywerewashedonceincold,double-distilledH20,oncein1mMEDTA(pH8.0),andtwicein50mMTricine(pH8.0).Thethylakoidmembraneswerethenresuspendedin0.3MTris(pH8.8)containing13%(v/v)glyceroland1%(w/v)SDS(SDS:Chl=10:1)andthen2%(w/v)DOCin0.3MTris(pH8.8)wasaddedtogiveaDOC:SDS:Chlof20:10:1.ThesolubilizedmembraneswereimmediatelysubjectedtoSDSpolyacrylamideslabgelelectrophoresisat4°CinthedarkaccordingtoWaldronandAnderson(26)toseparatethepigment-proteincomplexes.RoomtemperaturescansofthepigmentedcomplexesandtheircharacteristicabsorptionspectrawereobtainedusingaShimadzuUV-250spectrophotometer.TherelativeChlcontentsoftheindividualpigmentedcomplexesweredeterminedbyrelativepeakareas.DifferentialScanningCalorimetryofThylakoidMembranes.RHandRNHthylakoidswereisolatedasdescribedaboveandthenresuspendedinahighionicstrengthmediumcontaining50mMTricine(pH6.8),0.1Msorbitol,10mmNaCl,70mMKCI,5mMMgCl2,and20mM(-mercaptoethanoltoafinalChlconcentrationof2to3mgml-&.HeatcapacitymeasurementsweremadeinaMicrocal-1differentialscanningcalorimeter(MicrocalInc.,Amherst,MA)employingmatched1mlplatinumcells.A1mlaliquotoffreshlypreparedthylakoidmembraneswasaddedtoonecellandanequalvolumeofbufferintheothercell.Theheatingratewas1°Cmin-&.Heatcapacitywasdeter-minedfromtheintegratedpeakareaderivedfromacalibratedheatpulsedeliveredtothereferencecellofthecalorimeter.ElectronSpinResonance.Astocksolution(2mM)ofI(1,14)waspreparedinabsoluteethanolandstoredat-20°C.Tominimizethereductionofspinlabelpartitionedintothylakoids,themembraneswerefirsttakenupinresuspensionbuffer(50mMTricine[pH7.8],0.1Msorbitol,10mMNaCl,and5mMMgC12)containing10mMhydroxylamineandkeptoniceinthedarkfor5min.Attheendofthistreatment,thesuspensionwascentrifugedat4000gfor 5min,andthemembranesweretakenupinresuspensionbuffertoaconcentrationof2mgChl/ml.Forincorporationofspinlabel,201lofI(1,14)stocksolutionwereevaporatedontothebottomandsidesofa15x75mmdisposableculturetube,and200Alofthylakoidmembranesuspensionwereaddedtothesametube.Thetubewasvortexedintermittentlyfor5min,andthespinlabeledmembraneswerethentakenupintoa100Alcapillarytube,whichwassealedatoneendwithcapillarytubesealant(Miniseal)andplacedinthecavityofaVarianE-12ESRspectrometer.Spectrawererecordedat5and25°C,androtationalcorrelationtime(Tc)werecalcu-latedaccordingtothefollowingequation:Tc=6.5x10-`0w,[hI/h-)&-l]swherew,andhiarethewidthandheightofthelow-fieldspectrallineandh_,istheheightofthehigh-fieldspectralline(24).PreviousstudieswiththylakoidmembraneshaveindicatedthatthereisnochangeinthevalueofTcwhentwicethenormalconcentrationofspinprobeisused(i.e.40Mlratherthan20Mlofstocksolution)(22).Thiscanbeinterpretedasindicatingthatperturbationeffectsattributabletotheprobeitselfareminimal.Aswell,identicalTcvalueswereobtainedinthepresenceandabsenceof16mMchromiumoxalate,aspin-broadeningagentthateliminatesthewatersignalseeninthescans(5).Thisservesasacontrolonhowwelltheh_,valueismeasured.RESULTSLipidandFattyAcidComposition.TheresultsofTableIindicatethat,ingeneral,therewerenosignificantdifferencesinthelipidcontentofryeleavesdevelopedateither5or20C.Fattyacidanalysisofthevariouslipidclassesindicatedthatlinolenicacid(18:3)isthemajorunsaturatedfattyacidpresent.However,RHleavesexhibitedonlyaminimalincrease(2-9mol%)inthetotal18:3contentofthevariouslipids.Themostsignificantchangeinfattyacidcompositionwasthe74%decreaseinthetrans-16:1levelandtheaccompanying48%increaseinthepalmiticacidlevel(16:0)associatedwithPG.Sincetrans-16:1isthoughttobespecificallyassociatedwithchloroplastphotosyntheticmembranes(14),thelipidandfattyacidcom-positionofisolatedRHandRNHthylakoidswasexamined(TableII).ComparisonoftheresultsofTablesIandIIindicatethatthelipidcompositionofisolatedryethylakoidsexhibitedasignificantdecreaseinPCandPEcontentandaconcomitantincreaseinthecontentofDGDGandMGDGrelativetothatobservedfortotalleafextracts.ThiswasexpectedsinceDGDGandMGDGarethemajorlipidcomponentsofphotosyntheticmembranesfromhigherplants(14).Aswasobservedfortotalleafextracts,therewerenosignificantdifferencesinlipidcontentbetweenRHandRNHthylakoids.However,lowtemperaturedevelopmentappearedtoresultspecificallyina67%decreaseintrans-16:1levelswitha61%increasein16:0levelsassociatedwithPG.Thisresultedinatrans-16:1/16:0ofabout1.3inRNHthylakoidsincontrasttoatrans-16:1/16:0of0.3inRHthyla-koids.Thus,growthanddevelopmentofryeleavesatlowtem-peraturesappearstoresultinamajorandspecificdecreaseinthetrans-16:1levelassociatedwiththylakoids.Theminorincreases(2-8mol%)inthe18:3contentofRHthylakoid,MGDG,DGDG,andPGmayleadtochangesinthefluidityofthethylakoidmembranes.Therefore,themicroenvi-ronmentoftheRHandRNHlipidbilayerwascomparedbyelectronspinresonanceusingthespinlabelI(1,14).TheresultspresentedinTableIIIindicatethattherewasnosignificantdifferenceintherotationalcorrelationtime(Tc)forRHandRNHthylakoidsmeasuredateither25or5°C.Asexpected,both13
TableI.LipidandFattyAcidCompositionsofTotalLeafExtractsAllvalueswerecalculatedasmol%ofthetotal.Thedatarepresentthemeanoffivedifferentisolations±SD.RNHLeavesRHLeavesFattyacidprofileFattyacidprofileLipidLipid16:016:118:018:118:218:316:016:118:018:118:218:3mol%PC15±224±22±0.52±139±233±419±319±11±04±0.542±335±2PE5±131±51±0.41±0.439±428±45±220±31±02±0.441±237±4SL6±229±31±01±07±262±55±123±11±01±05±0.470±1DGDG25±48±0.51±01±03±0.487±126±16±01±01±02±091±1PG11±123±323±21±01±07±145±410±134±36±21±01±08±0.550±4MGDG38±21±0.5tiatr3±195±134±31±0trtr3±0.697±1atr,traceamountsonly(&0.5%).TableII.LipidandFattyAcidCompositionsofRHandRNHThylakoidsAllvalueswerecalculatedasmol%ofthetotal.Thedatarepresentthemeanofthreedifferentisolations±SD.RNHThylakoidsRHThylakoidsFattyacidprofileFattyacidprofileLipidLipid16:016:118:018:118:2 18:316:016:118:018:118:218:3mol%PC3±131±42±04±039±024±24±124±21±14±036±134±3PE1±038±103±41±130±829±82±133±12±13±127±137±2SL5±130±02±01±06±.062±16±127±31±11±04±167±4DGDG37±88±11±01±02±188±134±25±1tiatr1±093±1PG11±223±330±42±12±24±140±38±237±110±21+02±14±048±2MGDG43±61±1tr1±04±194±247±21±0tr1±02±096±1atr,traceamountsonly(&0.5%).TableIII.RotationalCorrelationTimes(Tc)forRHandRNHThylakoidMembranesLabeledwithI(1,14).Dataareexpressedasmeans±SDandareaveragesofatleastthreereplicatemeasurementsforasingleexperiment.Theexperimentswererepeatedthreetimesforthe25&Cdataandtwiceforthe5°Cdatawithsimilarresults.TcTemperatureRHthylakoidsRNHthylakoids°Cns251.61±0.131.74±0.0652.38±0.032.30±0.06RHandRNHthylakoidsexhibitedasignificantincreaseinTcduetoanincreasedorderwithinthelipidbilayerwhenthemeasuringtemperaturewasloweredfrom25to5C.Thus,theminorchangesinlipidunsaturationhavenotaffectedthefluidityofRHandRNHthylakoidssignificantly.Polarizationvaluesfordiphenyl-hexatriene-labeledRHandRNHthylakoidsobtainedasdescribedpreviously(22)alsorevealednosignificantdifferenceinfluidity(datanotshown).PolypeptideCompositionandChi-ProteinComplexes.TheresultsofTableIVindicatethattheproteinandpigmentcontentofRHandRNHthylakoidsarenotsignificantlydifferent.Grif-fithetal.(10)havereportedthatnosignificantdifferencesexistinthepolypeptidecompositionsofRHandRNHthylakoids.Photosyntheticpigmentsofthethylakoidmembranesareor-ganizedintospecificpigment-proteincomplexes(23,26).Elec-trophoreticseparationofChl-proteincomplexesfromRHandRNHthylakoidsaftermembranesolubilizationat0°CandaDOC:SDS:Chlof20:10:1indicatedthepresenceofsevenmajorChlbands(Fig.IA).TheabsorptionspectraofeachpigmentTableIV.CompositionofRHandRNHThylakoidsRHRNHReferenceChla/b2.96±0.22.99±0.2(17)Protein/Chl(mg/mg)7.1±1.26.8±2.9(10)Carotenoid/Chl0.092b0.096b(17)Chl/P700C530±53505±47(17)Chl/PQAd714(11)aMeasuredasugcarotenoid(mgChl)-&.bNotsignificantlydiffer-ent(P&0.05).cDeterminedbylight-minus-darkEPRspec-tra.dReferstoextractablePQAlevels.bandareillustratedinFigure1Bandareconsistentwiththefollowingassignments:peak1(CP1a)witharedabsorptionmaximumat675nmispresumedtobeanoligomericformofCPI;peak2,witharedabsorptionmaximumat675nmisthemajorChla-containingpigmentproteincomplex(CP1)associ-atedwithPSI(26);peaks3,4,and6,eachwithredabsorptionmaximaat673and652nmaretheoligomeric(LHCII,),dimeric(LHCII2),andmonomeric(LHCII3)formsofthelightharvestingChla/bpigmentproteinassociatedwithPSII(25);peak5,witharedabsorptionmaximumat671nmistheChlaproteinassociatedwithPSIIreactioncenters(CPa).Peak7containsfreepigment(FP)andistheresultofdetergentsolubilizationofthylakoids.WetestedaseriesofDOC:SDS:Chlratiosinordertomaximizeourelectrophoreticresolutionandconcomitantlymin-imizetheamountoffreepigmentobserved.TheoptimalratioforbothRHandRNHthylakoidswasfoundtobe20:10:1(DOC:SDS:Chl).Regardlessofthedetergentratioemployed,RHthylakoidstypicallyexhibitedslightlyhigherfreepigmentcon-tents(7-12%)thanRNHthylakoids(5-10%).However,themostconspicuousdifferencebetweentheChl-proteincomplexessep-aratedfromRHandRNHthylakoids(Fig.IA)wasthehigher14HUNE,RETAL.PlantPhysiol.Vol.84,1987
LOWTEMPERATUREDEVELOPMENTANDtrans-A3-HEXADECENOICACIDTableV.ChlContentofChl-ProteinComplexesSeparatedfromThylakoidsofRHandRNHLeavesAlldatarepresenttheaveragesofatleastthreereplicateseparationsofRHandRNHChl-proteincomplexes.TotalChlComplexRHleafNo.RNHleafNo.12313CPla18±316±211±220±318±2CP120±220±223±225±324±3LHCIII19±211±18±120±121±2LHCII311±418±121±19±210±4CPa11±112±112±113±112±2FP9±210±115±18±29±2LHCII,:LHCII31.730.610.382.222.10CPla:CPl0.900.800.480.800.75LUzIXX.500600WAVELENGTH(nm)FIG.1.A,GelscansofChl-proteincomplexesfromRNHandRHthylakoids.Peak1,CPpeak2,CP1;peak3,LHCII1;peak4,LHCII2;peak5,CPa;peak6,LHCII3;peak7,FP.B,Roomtemperatureabsorp-tionspectraoftheChl-proteincomplexes.ThenumberofthescancorrespondstothepeaknumberofFigureIA.proportionofLHCII,,presentinRNHthylakoids.TheLHCII1:LHCII3was1.85±0.18forRNHthylakoidsbutonly0.87±0.28forRHthylakoids.ThisdifferenceintheoligomericLHCII:monomericLHCIIwasstillmaintainedafternormaliza-tionofthedatawithrespecttoFPcontent(RNH=0.230+0.038;RH=0.058±0.026).Inaddition,theratioofCPla:CPlexhibitedasignificantdecreaseinRHthylakoids(0.58±0.11)comparedtoRNHthylakoids(0.97±0.09).Chl-ProteinComplexes,LeafOntogeny,andDevelopmentalTemperature.ThephenomenonofanalteredoligomericLHCII:monomericLHCIIwasfurtherinvestigatedbyexaminingChl-proteincomplexesasafunctionofleafontogeny.Kroletal.(18)haveshownthatunderourgrowthconditionstheprimaryleafofRHplantsfullyexpandsat20C,thesecondaryleafissubjectedtoexpansionatboth20and5°C,whereasthethirdleafisthefirstleafofRHplantswhichcompletelyexpandsat5°Conly.Thus,theprimaryleafexhibitsanatomicalandmorpho-logicalcharacteristicsofRNHleaves,whereasthethirdleafexhibitsfeaturescharacteristicofRHleaves(15).ThesecondaryleafisatransitionleafexhibitingfeaturesofbothRHandRNHleaves(15,18).TherelativeproportionsofChlpresentinthevariouscomplexesofRHandRNHthylakoidsisolatedfromleaves1,2,and3ispresentedinTableV.TheproportionofChlpresentinLHCII,andLHCII3wassignificantlyaffectedbythetemperatureexperiencedduringleafontogeny.Leaf3ofRHplantswhichwassubjectedtoexpansionat5°Conly,exhibitedanLHCII,:LHCII34-foldlowerthanleaf1ofRHplantswhichhadexpandedcompletelyat20°C.Incontrast,theLHCII,:LHCII3forthylakoidsisolatedfromleaf1and3ofRNHplantswasnotsignificantlydifferentandsimilartothatobservedforthylakoidsisolatedfromtheprimaryleafofRHplants.IncontrasttoLHCII,therelativeChlcontentsofthemajorChla-proteincomplexes,CPlandCPa,didnotappeartobeaffectedsignificantlybythetemperatureexperiencedduringleafontog-eny(TableV).However,theCP1acontentdidappeartobesensitivetodevelopmentaltemperature.TheCP1a:CPlwasabout2-foldlowerinthylakoidsisolatedfromleaf3thaninthylakoidsfromleaf1ofRHplants.SimilarresultswereobservedwhentheCPla:CP1ofthylakoidsofleaf3fromRHplantswascomparedtotheCPla:CP1ofthylakoidsfromleaf3fromRNHplants(TableV).Thus,thetemperatureexperiencedduringleafexpansionprimarilyaffectstheinvitroLHCIIorganizationandCPlacontent.TheeffectsofdevelopmentaltemperatureontheratioofoligomericLHCII:monomericLHCIIandCP1a:CPlwereex-tendedbyexaminingtheseratiosinthylakoidsfromtheupper-mostleavesofryeplantssubjectedtogrowthat20,15,10,and5°C.TheresultsinFigure2indicatethatadecreaseindevelop-mentaltemperatureresultedinaproportionaldecreaseinboththetrans-16:1contentassociatedwithPGandtheLHCII,:LHCII3.Thedecreaseintrans-16:1contentappearedtobecompensatedbyaproportionalincreaseinthe16:0contentofPG.ThelevelsoftheotherfattyacidsassociatedwithPGwerenotaffectedsignificantlybygrowthtemperature.Theap-parentcorrelationbetweenthetrans-16:1contentofPGandtheratioofoligomericLHCIItomonomericLHCII,wastestedbyplottingthemol%oftrans-16:1inPGasafunctionofoligomericLHCII:monomericLHCII.Allthedatawereobtainedfromtwoseparateexperimentsinwhichryeleaveswereallowedtodevelopat20,15,10,and50C.Figure3illustratesthatalinearrelation-shipwithanr2valueof0.930wasobtained.Thisindicatesastrongcorrelationbetweentrans-16:1contentinPGandLHCII,:LHCII3.Incontrast,CPla:CPlacontentdidnotappeartobeassensitivetogrowthtemperatureasLHCIIorganizationsinceasignificantdecreaseinCP1a:CPlwasobservedonlyatagrowthtemperaturebelow10°C(Fig.2).DifferentialScanningCalorimetryofIsolatedThylakoids.DSCofthylakoidmembranesisverysensitivetotheexperimen-talconditionsemployed.Forexample,DSCofRNHthylakoidsexhibitedfivedistincttransitionsbetween40and900CwhenmeasuredatpH6.8,highionicstrengthandinthepresenceofreducingagent(Fig.4,scan1).Incontrast,transitionAwasnotdetectedwhenRNHthylakoidswerescannedintheabsenceofAEt-.wUz4c0C#)oMIGRATION15
PlantPhysiol.Vol.84,198740r200CLHCII1:LHCII3CPla:CP120*ff20Zo_E401..Cz111o40IE201.16±.030.84±.07U.6S [0Cfl*fl1.04±.040.60*.092000M0r0FATTYACIDinPGFIG.2.FattyacidcompositionofPGasafunctionofdevelopmentaltemperatureinwinterrye.Seedlingsweregrownat20,15,10,or5°C.CalculatedratiosofLHCII,:LHCII3andCP1a:CP1wereobservedatthecorrespondinggrowthtemperatures.Whereindicated,datarepresentthemean±SD(n=2-3).._IL401-1ICQD3020h.2010-j0to4e*00651.0152.0LHCII1:LHC113FIG.3.Relationshipbetweentrans-16:1contentinPGandLHCII,:LCHII3.r2forthecurvewas0.930.ThedatawereobtainedfortheexperimentsdescribedinFigure3.f3-mercaptoethanol(Fig.4,scan3).However,transitionEbe-camemoreevidentintheabsenceofreducingagent(Fig.4,scan3).WhenRHandRNHthylakoidswerescannedatlowerionicstrengthandhigherpH(50mMTricine[pH7.8],10mmNaCl,5mMMgCI2,and0.Msorbitol)therewasamarkeddecreaseintheresolutionofalltransitionsbetween40and90°C(datanotpresented).Thus,formaximumresolutionandreproducibility,RNHandRHthylakoidswereroutinelyscannedatpH6.8,highionicstrengthandinthepresenceof20mM(i-mercaptoethanol(Fig.4,scansIand2).ThegeneralpatternofendothermsobservedforRHthylakoidsweresimilartothoseobservedforRNHthylakoids.However,DSCofRHthylakoidsconsistentlyexhibitedtwodistinguishingfeatures.First,theBandDtransi-tionswereresolvedasinflectionsratherthandistinctpeaks.Becauseofthis,accuratetransitiontemperaturescouldnotbedeterminedfortheseparticularendothermsinRHthylakoids(TableVI).Second,thetransitiontemperaturesdeterminedforendothermsAandFwere2to3ClowerinRHthylakoidsthanthoseobservedinRNHthylakoids(TableVI).FIG.4.DifferentialscanningcalorimetryofRHandRNHthylakoids.Scan1,RNHthylakoidsscannedinthepresenceof20mM,B-mercapto-scan2,RHthylakoidsscannedinthepresenceof20mM(B-scan3,RNHthylakoidsscannedintheabsenceofreducingagent.EndothermsarearbitrarilylabeledAtoF.Thelowtemperatureendotherm(preA-transition)originatesfromthylakoidlipidtransitions(19).NosignificantdifferencesinthepreA-transitiontemperaturesbetweenRHandRNHthylakoidsisconsistentwiththeelectronspinresonanceandthefluorescencepolarizationofDPH(datanotpresented)whichindicatedthatthemicroenvironmentofthebilayerlipidofRHandRNHthylakoidsappearstobeindistinguishable.DISCUSSIONPhosphatidylglycerolisthemajorphospholipidpresentinthylakoidmembranes(14)anditsbiosynthesishasrecentlybeenshowntotakeplacewithinisolatedchloroplasts(2).Thislipidischaracterizedbythepresenceoftheunusualfattyacid,trans-16:1,whichispresentonlyinplastids(14).LynchandThompson(20)haveshownthatshiftingthegrowthtemperatureofDunel-liellafrom30to12°CcausedasignificantchangeinthefattyacidmolecularspeciesassociatedwithPG.Wehavepresentedevidencethatgrowthanddevelopmentofryeatlow,cold-hardeningtemperaturesleadstoa67to74%decreaseinthetrans-16:1contentofPG.ThiswastheprincipalchangeinlipidandfattyacidcompositionthatweobservedbetweenRHandRNHthylakoids.Thus,wereportforthefirsttimethatgrowthanddevelopmentofryeatlow,cold-hardeningtemperaturesresultsinaveryspecificchangeinthefattyacidcompositionofPG.IncontrasttotherecentreportofVighetal.(29)whoreportedthatcold-hardeningofwheatresultsinthepresenceofunusual,long-chainfattyacids,wehaveexaminedtwovarietiesofrye,wheat,andseveraldicotyledonousplantspeciesandhavenotobservedthepresenceoftheselongchainfattyacidsassoci-16HUNERETAL.2
LOWTEMPERATUREDEVELOPMENTANDtrans-A3-HEXADECENOICACIDTableVI.TransitionTemperaturesfortheMajorEndothermsAssociatedwithIsolatedRHandRNHThylakoidMembranesBothRHandRNHsampleswerescannedinthepresenceof20mm0-mercaptoethanol.Datarepresenttheaverage±SDofthreedifferentexperiments.TransitionTemperaturepre-AABCDF°/CRNH10.8±1.446.6±0.559.4±0.667.2±0.473.3±1.286.1±0.6RH12.0±0.944.8±0.466.7±0.583.6±0.4atedwiththylakoidsupongrowthanddevelopmentatcold-hardeningtemperature.However,examinationofthefattyaciddatapresentedbyVighetal.(29)doesreveala69to84%decreaseinthetrans-16:1contentofPGuponcold-hardeningwhichtheauthorsdidnotpointout.Thedatapresentedinthisreportindicatethatgrowthatcold-hardeningtemperaturescausesasignificantdecreaseintheleveloftrans-16:1inPGandaconcomitantdecreaseinLHCII,:LHCII3.However,dotheinvitrodatatrulyreflectadevelopmentaltemperature-inducedchangeintheorganizationofryeLHCIIinsituor,rather,reflectadifferentialstabilityofoligomericLHCIItodetergentextraction?Thefollowingevi-denceindicatesthattheinsitustructuralorganizationaswellascertaininsitufunctionalcharacteristicsofLHCIIhavebeenalteredupongrowthanddevelopmentofryeatlowtemperatures.(a)Huneretal.(17)haveshownthattheEFfracturefaceofRNHthylakoidsexhibitsabimodalparticlesizedistributionwith150Aand100Aparticlessimilartothatreportedforthyla-koidsfromotherplantspecies(25).Incontrast,theEFfracturefaceofRHthylakoidsexhibitsaunimodalparticlesizedistribu-tionwithanaverageparticlesizeof136A.Staehelin(25)hasshownthattheEFparticlesofthylakoidsarecorrelatedwithPSII-LHCIIunits.Furthermore,Akoyunoglou(1)hascorrelated150AparticleswitholigomericLHCIIand135AparticleswithmonomericorintermediateformsofLHCII.(b)Huneretal.(17)haveshownthatRHandRNHchloroplastsaremorpholog-icallydistinct.RHcloroplastsexhibit,ontheaverage,smallergranalstacksthanRNHchloroplasts.LHCIIisthoughttobeimportantinthylakoidmembraneappression(9).(c)Griffithetal.(12)haveshownthatF685/F742wassignificantlyhigherinRHthylakoids(1.46)thanRNHthylakoids(1.19).Theseresultswereobservedwithnodetectabledifferenceinphotosyntheticunitsizebasedoninvitro(12,16,17)andinvivo(15)measurements.Argyroudi-AkoyunoglouandAkoyunoglou(3)havereportedthattheF685/F730ratioishighwhenmonomericLHCIIpredom-inatesandislowerwhenoligomericLHCIIpredominates.(d)Griffithetal.(12)recentlyreportedthatRHthylakoidsexhibitedadecreasedcapacityforenergytransferamongLHCII-PSIIunits.ThishasbeeninterpretedtoindicateadecreasedcooperativitybetweenLHCII-PSIIunitswithinRHthylakoids.However,RHthylakoidsexhibiteda33%higherrateofenergytransferwithinLHCII-PSIIunits.Thus,wesuggestthatthestructuralalterationsinLHCIIthatweobserveinvitroareconsistentwiththestruc-turalandfunctionalalterationsobservedinsitu.Recently,Huner(15)postulatedthatthestructuralalterationsinryethylakoidmembranesaftergrowthanddevelopmentatcold-hardeningtemperatures(12,13,17)reflectanalterationinmembraneorganizationratherthangrosscomposition.Thedatapresentedhereprovidefurthersupportforthishypothesis.First,DSCindicatedthattheoverallpatternofendothermsassociatedwithRHandRNHthylakoidswereverysimilar,whichisex-pectedconsideringthesimilaritiesinmembranelipidandpoly-peptidecomposition.However,theBandDtransitionsassoci-atedwithPSIIandLHCII,respectively,(PLow,personalcom-munication)werepoorlyresolvedandtheAandFendothermsexhibitedtemperaturetransitionswhichwere2to3°ClowerinRHthylakoidsthanRNHthylakoids.WesuggestthatthesedifferencesreflectchangesintheorganizationofvariousproteincomplexeswithinRHthylakoids.Specifically,growthtempera-tureclearlymodulatestheorganizationofLHCIIsuchthattheoligomericformpredominatesatthehighergrowthtemperaturewhereasthemonomericorsomeintermediateformpredomi-natesatthelowergrowthtemperature.Sincethetrans-16:1contentofPGexhibitssuchastrongcorrelationwiththesupra-molecularorganizationofryeLHCII,wesuggestthatdevelop-mentatcold-hardeningtemperaturesmodulatesLHCIIorgani-zationbyspecificallyalteringthetrans-16:1contentofPG.DubacqandTremolieres(9)presentedinvitrodatawhichindicatedthatthetrans-16:1contentofPGregulatestheorga-nizationofLHCII.Ourdataareconsistentwiththishypothesis.However,althoughwebelievethatPGisinvolvedinstabilizingLHCIIofryeinsitu,ourinvitroresultsclearlyindicatethatPGisnottheonlyfactorinvolvedinstabilizingLHCIIorganization.TheresultspresentedinFigure3indicatethattheLHCIIoligo-merLHCIImonomerisproportionaltotrans-16:1contentinPG.However,thecurvedoesnotpassthroughtheoriginwhichcanbeinterpretedtoindicatethateveninthetotalabsenceoftrans-16:1inPGtherestillcanexistasignificantcontentofoligomericLCHII.ThecalculatedvalueforoligomericLHCII:monomericLHCIIinthetotalabsenceoftrans-16:1inPGofrye(X-intercept)is0.63(Fig.3).Thus,incontrasttoDubacqandTremolieres(9)wesuggestthatPGanditstrans-16:1arenotobligatorybutappeartoenhancethestabilizationofoligomericLHCIIinryethylakoids.Recently,Somervilleetal.(6,21)havereportedthatamutantofArabidopsislackingtrans-16:1didnotexhibitanyapparentchangesinchloroplastmorphologyorchangesintheinvivoandinsitupropertiesofLHCIIasmeasuredbyChlfluorescence.Theyconcludethattrans-16:1isnotimportantinconferringuniquefunctionalorstructuralpropertiestoLHCIIinvivoandsuggestthatobservedchangesinLCHIII:LHCII3areaconse-quenceofinvitrodetergenteffects.Inthispaper,wepresentevidenceforaspecific,environmentallyinduceddecreaseinthetrans-16:1contentofPGinthylakoidsofwinterrye.IncontrasttoreportsbySomervilleetal.(6,21)onArabidopsis,thischangeinryethylakoidsiscorrelatedwithchangesinchloroplastmor-phologyaswellasinsituandinvitrochangesinthefunctionandorganizationofryeLHCII.However,preliminaryresultsclearlyindicatethatboththetrans-16:1contentofPGandtheorganizationofLHCIIareverysensitivetocold-hardeninggrowthtemperaturesinthemonocotyledonousplantsbutnotthedicotyledonousspeciesexaminedtodate(NPAHuner,JPWilliams,unpublisheddata).ItisinterestingtonotethatSomer-villeetal.(6,21)usedadicotyledonousspeciesintheirwork.Thus,weemphasizethattheproposedrolefortrans-16:1ofPGmaybecomeevidentonlyundercertainenvironmentalcondi-tionsand,moreimportant,webelievethatthisrolemaymanifestitselftovaryingdegreesindifferentplantspecies.Thiswillbethesubjectofaforthcomingpaper.Barberetal.(4,7,8)recentlyreportedthatthegrowthofpeas17
PlantPhysiol.Vol.84,1987andbarleyatcold(4-7°C)orwarm(17-25°C)temperaturesresultedinadoublingofthelipid/proteinratioanda1.4-foldincreaseinthetotallipid/Chlratio.Barber(4)proposedthattheincreaseoflipid-proteinratiosofthylakoidmembranesrepre-sentsanadaptationmechanismwherebythethylakoidmem-braneisabletomaintainamorefluidenvironmentatlowtemperature.Incontrast,weshowthatryethylakoidsdevelopedat5Cspecificallyexhibitasignificantreductioninthetrans-16:1contentofPG(TableII)andthatnosignificantchangesineitherryethylakoidprotein/Chl(TableIV)ortotallipid/Chlratioswereobservedupondevelopmentat5°C.Althoughthefattyaciddatapresentedheredoindicateminorchangesinthe18:3contentofSL,PG,DGDG,andMGDG,differentialscan-ningcalorimetry,electronspinresonanceandfluorescencepo-larizationmeasurementsindicatethatthesechangesdonotsig-nificantlyaffectthefluidityofRHandRNHthylakoids.Thus,ifthealterationoflipid/proteinratiosdoesindeedrepresentanadaptationtolowtemperaturesasproposedbyBarber(4),ourdataforryethylakoidsindicatethatitcannotbeconsideredageneraladaptivemechanism.Acknowledgments-TheauthorsareindebtedtoM.GriffithandK.Mitchellfortheirhelpwiththeinitialportionsofthiswork.WearegratefultoM.G.McLeod,ResearchStation,AgricultureCanada,SwiftCurrent,Saskatchewanforprovidingryeseeds.LITERATURECITED1.AKOYUNOGLOUG1984Thylakoidbiogenesisinhigherplants:assemblyandreorganization.InCSybesma,ed,AdvancesinPhotosynthesisResearch,VolIV.MartinusNijhoff/DrWJunk,TheHague,pp595-6022.ANDREWSJ,JBMUDD1985Phosphatidylglycerolsynthesisinpeachloroplasts.Pathwayandlocalization.PlantPhysiol79:259-2653.ARGYROUDI-AKOYUOGLOUJH,GAKOYUNOGLOU1983Supramolecularstruc-tureofchlorophyll-proteincomplexesinrelationtothechlorophyllafluo-rescenceofchloroplastsatroomtemperatureorliquidnitrogentemperature.ArchBiochemBiophys227:469-4774.BARBERJ1984Lateralheterogeneityofproteinsandlipidsinthethylakoidmembraneandimplicationsforelectrontransport.InCSybesma,ed,AdvancesinPhotosynthesisResearch,VolIII.MartinusNijhoff/DrWJunk,TheHague,pp91-975.BERGSP,DMNESBITT1979Chromiumoxalate:anewspinlabelbroadeningagentforusewiththylakoids.BiochimBiophysActa548:608-6156.BROWSEJ,PMCCOURT,CRSOMMERVILLE1985AmutantofArabidopsislackingachloroplast-specificlipid.Science227:763-7657.CHAPMANDJ,JDEFELICE,JBARBER1983InfluenceofwinterandsummergrowthconditionsonleafmembranelipidsofPisumsativumL.Planta157:218-2238.CHAPMANDJ,JDEFELICE,JBARBER1983Growthtemperatureeffectsonthylakoidmembranelipidandproteincontentofpeachloroplasts.PlantPhysiol72:225-2289.DUBACQJ-P,ATREMOLIERES1983Occuffenceandfunctionofphosphatidyl-glycerolcontaining3-trans-hexadecenoicacidinphotosyntheticlamellae.PhysiolVeg21:293-31210.GRIFFITHM,GNBROWN,NPAHUNER1982Structuralchangesinthylakoidproteinsduringcoldacclimationandfreezingofwinterrye(SecalecerealeLcvPuma).PlantPhysiol70:418-42311.GRIFFITHM,BELFMAN,ELCAMM1984AccumulationofplastoquinoneAduringlowtemperaturegrowthofwinterrye.PlantPhysiol74:727-72912.GRIFFITHM,NPAHUNER,DJKYLE1984FluorescencepropertiesindicatethatphotosystemIIreactioncentersandlight-harvestingcomplexaremod-ifiedbylowtemperaturegrowthinwinterrye.PlantPhysiol76:381-38513.GRIFFITHM,NPAHUNER,DBHAYDEN1986Lowtemperaturedevelopmentofwinterryeleavesaltersthedetergentsolubilizationofthylakoidmem-branes.PlantPhysiol81:471-47714.HARWOODJL1980Plantacyllipids:structure,distributionandanalysis.InPKStumpf,EEConn,eds,TheBiochemistryofPlants,Vol4.AcademicPress,NewYork,pp1-5515.HUNERNPA1985Morphological,anatomicalandmolecularconsequencesofgrowthanddevelopmentatlowtemperatureinSecalecerealeLcvPuma.AmJBot72:16.HUNERNPA1985Acclimationofwinterryetocold-hardeningtemperaturesresultsinanincreasedcapacityforphotosyntheticelectrontransport.CanJBot63:506-51117.HUNERNPA,BELFMAN,MKROL,AMCINTOSH1984Growthanddevelop-mentatcold-hardeningtemperatures.Chloroplastultrastructure,pigmentcontentandcomposition.CanJBot62:53-6018.KROLM,MGRIFFITH,NPAHUNER1984Anappropriatephysiologicalcontrolforenvironmentaltemperaturestudies:growthkineticsofwinterrye.CanJBot62:19.LowPS,DRORT,WACRAMER,JWHITMARSH,BMARTIN1984Searchforanendotherminchloroplastlamellarmembranesassociatedwithchilling-inhibitionofphotosynthesis.ArchBiochemBiophys231:336-34420.LYNCHDV,GATHOMPSON1984ChloroplastphospholipidmolecularspeciesalterationsduringlowtemperatureacclimationinDunaliella.PlantPhysiol74:198-20321.MCCOURTP,JBROWSE,JWATSON,CJARNTZEN,CRSOMMERVILLE1985AnalysisofphotosyntheticantennafunctioninamutantofArabidopsisthaliana(L)lackingtrans-hexadeneoicacid.PlantPhysiol78:853-85822.McRAEDG,JACHAMBERS,JETHOMPSON1985Senescence-relatedchangesinphotosyntheticelectrontransportarenotduetoalterationsinthylakoidfluidity.BiochimBiophysActa810:200-20823.MULLETJE,JJBURKE,CJARNTZEN1980ChlorophyllproteinsofphotosystemI.PlantPhysiol65:814-82224.RULEGS,JKRUUV,JRLEPOCK1979MembranelipidfluidityislimitingintheconcanavalinA-mediatedagglutinationofpyBHKcells.BiochimBio-physActa556:399-40725.STAEHELINLA1981Freeze-fracturestudiesofgreenplantandprochloronthylakoids.Astatusreport.InGAkoyunoglou,ed,StructureandMolecularOrganizatio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&It has been widely recognized that 16:1v3t has a decisive influence on phase transition temperature of membrane lipid (Thompson, 1996). The results of the cold acclimation research of winter rye by Huner (Huner et al., 1987) also showed that the decrease of 16:1v3t at low temperature caused the depolymerization of LHC II oligomer resulting in a decline in light-harvesting efficiency. The content of 16:1v3t in thylakoid membranes of ICE-L decreased with cold stress, consistent with previous results and observations. &ABSTRACT: Ice algae have successfully adapted to the extreme environmental conditions in the Antarctic, however the underlying mechanisms involved in the regulation and response of thylakoid membranes and chloroplast to low-temperature stress are still not well understood. In this study, changes in pigment concentrations, lipids, fatty acids and pigment protein complexes in thylakoid membranes and chloroplast after exposure to low temperature conditions were investigated using the Antarctic ice algae
Chlamydomonas
sp. ICE-L. Results showed that the chloroplasts of
Chlamydomonas
sp. ICE-L are distributed throughout the cell except in the nuclear region in the form of thylakoid lamellas which exists in the gap between organelles and the starch granules. Also, the structure of mitochondria has no obvious change after cold stress. Concentrations of Chl
, monogalactosyl diacylglycerol, digalactosyl diacylglycerol and fatty acids were also observed to exhibit changes with temperature, suggesting possible adaptations to cold environments. The light harvesting complex, lutein and β-carotene played an important role for adaptation of ICE-L, and increasing of monogalactosyl diacylglycerol and digalactosyl diacylglycerol improved the overall degree of unsaturation of thylakoid membranes, thereby maintaining liquidity of thylakoid membranes. The pigments, lipids, fatty acids and pigment-protein complexes maintained the stability of the thylakoid membranes and the normal physiological function of
Chlamydomonas
sp. ICE-L. Full-text · Article · May 2016 +4 more authors ...&One of the environmental factors that strongly influences the thylakoid membrane fluidity (by changing the lipid composition) is the temperature, as it has been shown that the cold-grown plants have more fluid thylakoids than those grown at higher temperatures (Barber et al., 1984). The environmental temperature induces changes in the organization of thylakoid membrane complexes, which influence their thermostability (Huner et al., 1987; Ruelland and Zachowski, 2010). The absorption spectra of isolated thylakoid membranes with quercetin at different pH of the medium demonstrate a minor red shift and a decrease in the Chl a absorption bands at acidic and physiological pH in comparison to alkaline pH (Fig. 1). &ABSTRACT: The effect of the exogenously added quercetin against the UV-B inhibition of the photosystem II (PSII) functions in isolated pea thylakoid membranes suspended at different pH of the medium (6.5, 7.6 and 8.4) was investigated. The data revealed that the interaction of this flavonoid with the membranes depends on the pH and influences the initial S0-S1 state distribution of PSII in the dark, the energy transfer between pigment-protein complexes of the photosynthetic apparatus and the membrane fluidity. Quercetin also displays a different UV-protective effect depending on its location in the membranes, as the effect is more pronounced at pH 8.4 when it is located at the membrane surface. The results suggest that quercetin induces structural changes in thylakoid membranes, one of the possible reasons for its protection of the photosynthetic apparatus.
Copyright (C) 2015 Elsevier GmbH. All rights reserved. Full-text · Article · Jul 2015 &One of the environmental factors that strongly influences the thylakoid membrane fluidity (by changing the lipid composition) is the temperature, as it has been shown that the cold-grown plants have more fluid thylakoids than those grown at higher temperatures (Barber et al., 1984). The environmental temperature induces changes in the organization of thylakoid membrane complexes, which influence their thermostability (Huner et al., 1987; Ruelland and Zachowski, 2010). &ABSTRACT: Abstract
The effect of the exogenously added quercetin against the UV-B inhibition of the photosystem II (PSII) functions in isolated pea thylakoid membranes suspended at different pH of the medium (6.5, 7.6 and 8.4) was investigated. The data revealed that the interaction of this flavonoid with the membranes depends on the pH and influences the initial S0–S1 state distribution of PSII in the dark, the energy transfer between pigment-protein complexes of the photosynthetic apparatus and the membrane fluidity. Quercetin also displays a different UV-protective effect depending on its location in the membranes, as the effect is more pronounced at pH 8.4 when it is located at the membrane surface. The results suggest that quercetin induces structural changes in thylakoid membranes, one of the possible reasons for its protection of the photosynthetic apparatus.Article · Jul 2015 ChapterNovember 2016+3 more authors…ArticleNovember 2016 · Plant physiology · Impact Factor: 6.84+3 more authors…ChapterNovember 2016ArticleNovember 2016 · Photosynthesis Research · Impact Factor: 3.50Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.This publication is from a journal that may support self archiving.Last Updated: 13 Oct 16
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