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1、杜仲叶片衰老过程中的细胞程序性死亡ProgrammedCellDeathduringLeafSenescenceinEucommiaulmoidesOliv.*Foundationitems:JunZhengFudationofPekingUniversity生命科学学院植物分子与发育学系98级江枫AbstractLeaftissuesfromEucommiaulmoidesOliv.treeswereusedtostudythemechanismofprogrammedcelldeath(PCD)duringleafsenescence.Here,weshowthatDNA
2、laddersweredetectedbygelelectrophoresisonlyinsenescentleaves.DNAfragmentationandnuclearDNAcondensationwerefurtherconfirmedbyusingtheterminaldeoxynucleotidyltransferase(TdT)-mediateddUTPnickendinsitulabeling(TUNEL)method.A20kDaDNasewasdetectedonlyinsenescentleaves,whichsuggestedthatfragmente
3、dDNAwouldbecausedbythisDNase.Keywords:DNase―Leafsenescence―Programmedcelldeath(PCD)―EucommiaulmoidesOliv.Celldeathisabasicbiologicalprocessthatfunctionsinmanyaspectsofanimalandplantdevelopmentandintheirresponsestostress(Greenberg1996,Wangetal.1996,MartinsandEarnshaw1997).Studiesonanimalshav
4、eshownthattheexecutionofprogrammedcelldeath(PCD)orapoptosisiscontrolledbyamultistepsignalingpathway(McConkeyandOrrenius1994,Stewart1994).Likeinanimals,itiscalledasphysiologicalcelldeathfordevelopmentanddefense(Greenberg1996),soitmaybethatanycomplexmulticellularorganismwillbefoundcelldeathau
5、sufulprocesstohaveinitsrepertoire.Therearemanyexamplesonprogrammedcelldeathduringplantdevelopment,suchassenescenceofthecarpelandpetal(OrzáezandGranell1997a,b),xylogenesis(MittlerandLam1995,Fukuda1996,1997,WangandCui,1998),aleuronedeletion(Wang,M.etal.1996),thedeathoftherootcapcells(Wang,H.e
6、tal.1996)andsomaticembryogenesis(McCabeetal.1997).Leafsenescenceisthefinalstageofleafdevelopment,whichhasbeenthoughttobeatypeofprogrammedcelldeath(NoodénandLeopold1978,GanandAmasico1997).Themechanismwhichcontrolsthisprocessmustbegeneticallyregulatedbyautonomous(internal)factorssuchasage,rep
7、roductivedevelopmentandphytohormonelevels,aswellasregulatedbyenvironmentalsignalssuchasstresses,drought,ozone,nutrientdeficiency,pathogeninfection,woundingandshading(GanandAmasico1997).Atthemolecularlevel,tillnow,morethan30leafsenescenceassociatedgenes(S
