FRST 302 Paper FINAL VERSIONWord文档格式.docx

FRST 302 Paper FINAL VERSIONWord文档格式.docx

《FRST 302 Paper FINAL VERSIONWord文档格式.docx》由会员分享，可在线阅读，更多相关《FRST 302 Paper FINAL VERSIONWord文档格式.docx（15页珍藏版）》请在冰豆网上搜索。

RiccardoWangPan48766117

March29,2011

FRST302

TableofContents

TableofContents1

Introduction2

EpigeneticEffectsofTemperatureandParentalEnvironment3

CaseStudy:

Pinussylvestris3

EpigeneticEffectsandColdTolerance5

EpigeneticsEffectsandSaltStress7

ComparativeInvestigationofMangroves,Rice,andWheat7

MangrovesLagunculariaracemosa8

RiceIndiciasppcs.9

WheatTriticumaestivum10

EpigeneticControlinConifers12

EpigeneticInsightsintoPiceaabies13

Discussion15

Conclusion16

WorkCited17

Introduction

Epigeneticsisarelativelynewfieldofstudythatfitsbetweendevelopmentalbiologyandgenetics（Holliday2006）.Itessentiallylooksintohowenvironmentalfactorshavetheabilitytoalterattributesofanoffspringduringgestation（ScienceDaily2009）.Anotherwaytodescribethisisanalterationtothephenotypethatisnotaccountedforbygenes（Felsenfeld2006）.ThemechanismsofhowthisisachievedarepresentattheDNAlevelaswellastheproteinlevel,specificallyhistones/chromatin（Holliday2005）.

DNAsequencesaswellashistonepackagesarealteredduetothefactthattheybecomemethylatedoracetylated（ScienceDaily2009）.Thismethylationinturncanbeheritable.Twomajorprincipleshavebeenidentifiedasbeingpivotaltoepigeneticmechanics.Oneisthatthephenotypicexpressioniscontrolledbyanon,offtypeofcontrol.Thesequenceorproteinalteration/methylationiseitherpresentornot.Felsenfelddescribesitas‘formequalsfunction.’Thesecondisthatthesealterationsmusthaveamechanismbywhichtheycansustainthemselvesinthatpositionregardlessofentropyandgrowth.Thesepointshavebeenthemainfocusofalotofepigeneticresearchtodate（Felsenfeld2006）.

InthekingdomPlantae,alloftheepigeneticmechanismsareusedextensively,soplantshavebeenfoundtobegoodmodelsforresearch（Allisetal.2007）.Itisunderstandablethatplantsmakeuseofepigeneticsastheyarequitenotablydevelopmentallyplastic.Similaritiesbetweenplantsandanimals,specificallygenomesize,complexities,heterochromatinlevelsandDNAcytosinemethylationlendstopossibleextrapolationsfromplantresearchtothatofanimalsandhumans.Plantsalsojustprovideaninterestingplatformforresearchduetotheuniquenessofsomeoftheirgeneticfeatures.Forexample,unlikeanimals,plantspossessalifestagebetweenmeiosisandfertilizationinwhichtheyundergomitoticdivisions;

itishighlypossiblethatepigeneticmarkingcanoccurhere.Also,plantshaveuniqueclonalandmeristematicproperties.Somaticembryogenesisinparticularprovidesagoodplatformforepigenetics.Thirdly,epigenetictransmissionseemstobeeasierinplantsduetothepresenceofplasmodesmata（Allisetal.2007）.

Basedonthesepointsontheproficiencyofplantsinepigeneticresearch,itisunderstandablethattherehavebeensubstantialcontributionstothefield.Historyofepigeneticsinplantsisstrong.Forexample,theobservationofheritablebutreversiblechangesintomatoesandmaizewasamongthefirsttopointtonon-Mendeliangenetics.Parentalimprintingofindividualgeneswasalsofirstseeninmaize.TherehasalsobeensignificantresearchconductedonplantsinrelationtoposttranscriptionalgenesilencingwhichistheplantequivalentofRNAinterference（Allisetal.2007）.

Thispaperwillhighlightfouruniquecasestudiesthatexploretherelationshipbetweenplantsandepigenetics.

EpigeneticEffectsofTemperatureandParentalEnvironment

Pinussylvestris

Epigeneticsisthoughttohavethepotentialtoaffecttheadaptationattributesoftreeprogeniesandresearchersaretryingtoprovethishypothesis.Likethosewhoprovedtheeffectsofepigeneticsbyfindingoutthatenvironmentalconditionsinfluencesclimaticadaptation（Johnsen2005）,theimpactofparentalenvironmentonprogeniesisusedtoprovetheepigeneticeffectsonprogenies.ThecasestudyofPinussylvestrisfocusesontheimpactofparentalenvironmentonprogeniesandfocusesonworkbyDormlingandJohnsen（1992）whotestedparentalenvironmentaleffectstoexplainhowtheparentalenvironmentaffectstheirprogenies.

DormlingandJohnsen（1992）wereattemptingtofindoutiftheenvironmentswherePinussylvestrisweregrowingwouldaffecttheattributesoftheirprogeniesandifanyeffectwilldecreasewithtime.Theywereinterestedifseedweightcouldrepresentaftereffectofepigeneticresponseandcomparefamilyeffect,reciprocalseffect,andlocalityeffect.

DormlingandJohnsen（1992）establishedfiveexperimentsandparentalplantsgrewupinthreeclonalarchives,locatedinsouthern,centralandnorthernSwedenpriortoexperimentinitiation.Seedproducedafterreciprocalcrossesindifferentageswerecollectedandseedsweretreatedintwophases.Inthefirstphase,thegerminationoftheprogenyplantswereexposedtoa20hourphotoperiod,a4hourdarkperiod,atatemperatureof25oCand15oC,respectively,fortwoweeks.Inthesecondphase,lasting10to11weeks,favorableconditionsweremaintainedatatemperatureof25oCfor16hoursand15oCwitha20hourphotoperiodand4hourdarkperiod.DuringthisphaseP.sylvestrisdevelopedtheirterminalbuds.Inexperiment1to3,thedarkperiodincreased1houreveryweekandattheendofthisphase,theplantswereexposedtoan8hourphotoperiodat25oCand16hoursdarkperiodat5oC.Plantgrowthstopedduringthisperiod.Whentheplantssufferfrom14hoursphotoperiodand10hournight,thedegreeofhardnessistested.

Inexperiments4to5,thefirstgrowthperiodisstoppedbythefollowingsteps:

nightforplantsincreasesfor1houreveryweekuntila11hourphotoperiodgrowingataratioof15:

5oC（day:

night）.Afterthis,theenvironmentchangesto8hoursphotoperiodwith15oCand16hoursdarkperiodwith5oCfor3weeks.Afterthis,plantsareexposedtoa8hourphotoperiodwith25oCand16hoursdarkperiodwith5oCfor1week,of24hoursdarkperiodwith5oCfor2weeksandof8hoursphotoperiodwith25oCand16hoursdarkperiodwith5oCfor1week.Thenbeginsthesecondgrowthperiod,plantsgrowunder8hoursphotoperiodwith25oCand16hoursdarkperiodwith5oCfor3week.Thenthedarkperiodincreasesfor1hourseveryweek.Whentheplantssufferfrom12hoursphotoperiodand12hoursnight,thedegreeofhardinessistested.Thestatisticsoffrosthardinessoftheplantsareanalyzedafterwardsbetween1982and1984.

DormlingandJohnsen（1992）foundthat,thefamilyofplantsdoesnotsignificantlyaffecttheweightandreciprocaleffectismoresignificant.Theyearoftheseedsandthelocationlargelyaffectedtheseedweight.Inthefirstgrowingperiod,familyeffectwasmoresignificantthanthedifferencesbetweenlocations.Inthesecondgrowingperiod,localitylargelyaffectstheheightoftheplantsandfamilyeffectswerealsosignificant.Onlyfamilyeffectwasobservedduringtheperiodbeforebudding.Totestforestdamageafterthefirstperiodofgrowing,familyeffectwasstillmostsignificantandlocalityalsoaffectedit.Seedfromthenorthwasobservedtobemoreresistantandfamilyeffectwasonlysignificant.

Toconclude,parentalenvironmentaffectsprogenies.Duringthefirstgrowingperiod,seedweight,howtheplantsgrewandhowtheplantsadaptedtofrostdamagewassignificantlyaffectedbytheenvironmentwheretheirparentsgrow.Duringthesecondgrowingperiod,theenvironmentonlyaffectstheheightoftheplantsbutitdecreasedovertime.Secondly,familyeffectsaremoresignificantthanlocaleffectsinhowP.sylvestrisgrowsandhowtheyfacefrostdamage.Lastly,thereciprocaleffectisonlyobviousinseedweight,andthisonlyslightlyaffectshowplantsgrowanddoesnotaffecttheplantsfrosthardiness.Thereforenorelationshipbetweenseedweightandfrosthardinessisevident.

Therefore,thiscaseestablishesthatparentalenvironmentaffectsprogeniesandtheeffectdecreaseswhentheprogeniesgrow.Inotherwords,theexistenceofparentaleffectsprovesanepigeneticinteractionbetweenparentsandprogenies,asepigeneticscanaffecttheprogeniesattributes.

EpigeneticEffectsandColdTolerance

Inrecentyears,throughcontinualfindingsinthefieldofepigenetic,leadsonetobelievethatplantsmayhaveashort-termresponseplantowardsstressaswellasrecognitioninthefuture.EpigeneticinheritanceisachangeingenefunctionthatdoesnotentailachangeintheDNAsequence（Jablonkaetal2002）.Thisstudyoftemporalmechanismsandspecialgenecontrolisanimportantcomponentinthedevelopmentofcomplexorganisms.Modificationsthroughepigeneticisnotrestrictedtojusttheexposureofstressinplantsbutalsocontinuesfromonegenerationtothenext.Whenexposedtostress,itislikelythattheformationofepiallelesandparamutationswillremainandcausetheemergenceofnewplantecotypes.Continualdivergenceovermanygenerationsresultsingeneevolutionthatbetteradapttotheirexposuretostress（Boyka&

Kovalchuk2008）.Inthefollowingsection,themechanismsasaresultofcoldrelatedstressesishighlighted.

Thecontinualexposureofplantstocoldenvironmentsresultsinanepigeneticchange-plantsareabletomeasurethecoldduringthewinterseasonaswellasrecognizingthisexposureinthecomingspring（Sungetal.2004）.Thissurvivalabilityrequiresthedemandsfortheimprovementorcreationofhigherresistanceandtolerancequalities.