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《植物细胞全能性.ppt》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、CellTotipotency植物学-易欣S091573细胞全能性（celltotipotency）比较权威的定义是1984年国际组织培养协会做出的：“细胞全能性为细胞的某种特征，有这种能力的细胞保留形成有机体所有细胞类型的能力”。Germcellsareoftendescribedastheultimatetotipotentstemcell.Thetotipotentpotentialofgermcellsisevidentinthematureeggsofmanyanimals,wheresomaticgen
2、eproducts,includingthoserequiredforthepatterningoftheearlyembryo,arepresentbutnotutilizeduntilfertilization.Therearethreefeaturescontributetothegermcell’suniqueabilitytoretainthetotipotentpotentialnecessaryfortheconceptionofanentirelyneworganism.1、Transcriptio
3、nalRepressionRestrictsGermCellFate2、GermCellsRelyonTheirNiche3、ConservedRegulatorsControltheGermCellProgramTranscriptionalRepressionRestrictsGermCellFateTranscriptionalRepressionRestrictsGermCellFateGermCellsRelyonTheirNicheThenicheprovidesthenecessarysignalst
4、hatregulatethebalancebetweenself-renewalanddifferentiationthatisneededforproperprogressionthroughgametogenesis.GermCellsRelyonTheirNicheConservedRegulatorsControltheGermCellProgrammRNAscodingforessentialgermlinefactorshavebeenidentifiedingermgranules,andmanyof
5、theproteincomponentsofgermgranulesareimplicatedinvariousaspectsofmRNAregulation.Thespecificmechanismsinvolved,however,remainpoorlyunderstoodandarelikelytobecomplex.ConservedRegulatorsControltheGermCellProgramConservedRegulatorsControltheGermCellProgramConserve
6、dRegulatorsControltheGermCellProgramForexample,theDEADboxhelicaseVasa,awidelyconservedcomponentofgermgranules,isrequiredfortheexpressionofseveralproteinsinDrosophila,includingGurkeninoocytesandNanosinthegermplasmofembryos.ConservedRegulatorsControltheGermCellP
7、rogramVasaregulationofGurkendependsonaninteractionwiththetranslationfactoreIF5B,suggestingthatVasafunctionsdirectlyinthetranslationalactivationofGurkenRNA.ConservedRegulatorsControltheGermCellProgramVasaregulationofNanos,however,doesnotrequirebindingtoeIF5Bbut
8、requiresrecruitmentofothergermgranulecomponentstothegermplasm,includingTudor.AdraftgeneregulatorynetworkforcellulartotipotencyreprogrammingControls(orfunctionallinks,relationships,
