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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,wesh
2、owthatDNAladdersweredetectedbygelelectrophoresisonlyinsenescentleaves.DNAfragmentationandnuclearDNAcondensationwerefurtherconfirmedbyusingtheterminaldeoxynucleotidyltransferase(TdT)-mediateddUTPnickendinsitulabeling(TUNEL)method.A20kDaDNasewasdetectedonlyinsenescentleaves,whichsugg
3、estedthatfragmentedDNAwouldbecausedbythisDNase.Keywords:DNase―Leafsenescence―Programmedcelldeath(PCD)―EucommiaulmoidesOliv.Celldeathisabasicbiologicalprocessthatfunctionsinmanyaspectsofanimalandplantdevelopmentandintheirresponsestostress(Greenberg1996,Wangetal.1996,MartinsandEarnsh
4、aw1997).Studiesonanimalshaveshownthattheexecutionofprogrammedcelldeath(PCD)orapoptosisiscontrolledbyamultistepsignalingpathway(McConkeyandOrrenius1994,Stewart1994).Likeinanimals,itiscalledasphysiologicalcelldeathfordevelopmentanddefense(Greenberg1996),soitmaybethatanycomplexmultice
5、llularorganismwillbefoundcelldeathausufulprocesstohaveinitsrepertoire.Therearemanyexamplesonprogrammedcelldeathduringplantdevelopment,suchassenescenceofthecarpelandpetal(OrzáezandGranell1997a,b),xylogenesis(MittlerandLam1995,Fukuda1996,1997,WangandCui,1998),aleuronedeletion(Wang,M.
6、etal.1996),thedeathoftherootcapcells(Wang,H.etal.1996)andsomaticembryogenesis(McCabeetal.1997).Leafsenescenceisthefinalstageofleafdevelopment,whichhasbeenthoughttobeatypeofprogrammedcelldeath(NoodénandLeopold1978,GanandAmasico1997).Themechanismwhichcontrolsthisprocessmustbegenetica
7、llyregulatedbyautonomous(internal)factorssuchasage,reproductivedevelopmentandphytohormonelevels,aswellasregulatedbyenvironmentalsignalssuchasstresses,drought,ozone,nutrientdeficiency,pathogeninfection,woundingandshading(GanandAmasico1997).Atthemolecularlevel,tillnow,morethan30leafs
8、enescenceassociatedgenes(S
