MolecularControlofArabidopsisTrichomesDevelopment姓名：王巖學(xué)號(hào)：2014051614生命學(xué)院遺傳專業(yè)1Maincontent1.abstractabouttrichomesinArabidopsis2.theprocessoftrichomesdevelopment3.molecularcontrolofArabidopsistrichomesdevelopment4.conclusion21.Abstract:

InArabidopsis,trichomesaretypicallyunicellularstructuresandproducedonnearlyalltheaerialorgansexceptforthehypocotylandthecotyledons.Itsfunctionisprotectionagainstplant-eatinganimalsattack.Inthelasttwodecades,molecularmechanismsinvolvedintheinitiationanddevelopmentoftrichomeshavebeeninvestigatedwiththeobjectiveofanalyzingfactorscontrollingcellfateanddifferentiationinplantcells.Withtheavailabilityofalargenumberoftrichome-relatedmutantsinArabidopsis,manykeyregulatorscontrollingtrichomeformationhavebeenidentified.InArabidopsis,trichomesonrosetteleavesarelargesinglecells,usuallywiththreebranches,anduntilnowhavebeenthesubjectofresearch.342.發(fā)育過程建立在形態(tài)學(xué)標(biāo)準(zhǔn)基礎(chǔ)上,擬南芥表皮毛發(fā)育分為6個(gè)階段:階段1:最開始,一個(gè)定向的表皮細(xì)胞相對(duì)于周圍的表皮細(xì)胞快速膨脹(圖1A),細(xì)胞核進(jìn)行核內(nèi)復(fù)制。表皮毛細(xì)胞之間大約相隔3-4個(gè)細(xì)胞階段2:當(dāng)表皮毛前期細(xì)胞擴(kuò)展到比周圍細(xì)胞直徑大2–3倍時(shí),開始出現(xiàn)垂直于表皮細(xì)胞層面的凸起,產(chǎn)生了表皮毛細(xì)胞的桿狀結(jié)構(gòu)(圖1A)。階段3:緊接著,正在生長的細(xì)胞頂端發(fā)育出細(xì)胞增大的共軛焦點(diǎn),表皮毛分支開始發(fā)生(圖1A)。擬南芥葉表皮毛根據(jù)地理品系一般會(huì)形成2–4個(gè)分支。分支的方向與葉片基部到頂部軸向相互對(duì)齊,且分支間的角度非常規(guī)則階段4:在所有分支發(fā)生后,細(xì)胞通過彌散性生長繼續(xù)增大,這樣該細(xì)胞在直徑和高度上就會(huì)有所增大。開始,正在生長的表皮毛分支是鈍的(圖1A)表皮毛細(xì)胞形態(tài)發(fā)生的不同發(fā)育階段(每個(gè)細(xì)胞右下角的數(shù)字表示特定的發(fā)育階段)5階段5:頂端逐漸變尖(圖1B)階段6:在細(xì)胞增大停止后,表皮毛細(xì)胞表面形成數(shù)量不等的乳突(圖1B),周圍由1圈表皮支持細(xì)胞圍繞63.Arabidopsistrichomes:amodeloftrichomedevelopmentandregulationtheactivator–inhibitormechanism:Initialepidermalcellsequivalentlyexpresstrichome-promotingfactors,whichcanactivaterepressorsbutresultindifferentcellfateintheneighboringcells.Numeroustrichome-relatedmutantshaveenabledtheidentificationofmanytrichomepatterninggenes,whichcanbedividedintotwotypes:trichome-positiveandtrichome-negativeregulators.InArabidopsis,oneregulatorymodelshavebeenidentifiedintrichomeformationthatistheactivator–inhibitormodel.71)ThepositiveregulatorsincludetheR2R3MYBtranscriptionfactor

GL1,thebHLHfactorGL3andtheWD40-factorTTG1.GL1andTTG1interactwithGL3,formingaMYB/bHLH/WDcomplex.ThisregulatorycomplexstimulatesepidermalcellstodifferentiateintotrichomesbyactivatingtheexpressionofitsdownstreamactivatorsGL2andTTG2.whichencodesahomeodomain-leucinezipper(HD-Zip)andaWRKYtranscriptionfactorindividually.

2)Thenegativeregulatorsarerepresentedbysixredundantlyactinggenes:CPC,TRY,ETC1,ETC2,ETC3andTCL1.AllofwhichencodesinglerepeatR3MYBproteins.8ThesesmallsizedinhibitorscanmovelaterallyintoneighboringcellsandcompetewithGL1forbindingtoGL3,forminganinactivatingcomplex,whichcannotpromoteGL2andTTG2expression,therebyinhibitingtrichomefate.3)ItwasreportedthatGL1andGL3containaDNA-bindingdomain,respectively,anddeletionoftheDNA-bindingdomainscompletelyrepressestheexpressionoftheirdownstreamgeneGL2,suggestingthatGL2maybepositivelyregulatedbythemthroughDNA–proteinbinding.Thereafter,itwassuggestedthatGL1directlybindstothepromotersofGL2,whichcorrespondstothefindingthatTTG2isdirectlyregulatedbyGL1.Simultaneously,bothTTG1andGL3weredemonstratedtointeractwiththepromotersofTTG2.9

TTG1candirectlyactivatetheGL3/GL1transcription,indicatingthatTTG1mayactupstreamofGL3andGL1.Moreover,GL3wasfoundtobindtoitsownpromoterandanauto-inhibitionwasshownforthisgeneusingco-transfectionassaysinprotoplasts.Thesefindingsfurtherourunderstandingoftheactivator–inhibitormechanismoftrichomeformation.4.結(jié)語：擬南芥表皮毛作為一種特化的、典型的單細(xì)胞表皮毛,其發(fā)育過程簡單,在植物表面的分布有一定模式,其突變體不改變植物發(fā)育的其它性狀而便于遺傳分析,所以擬南芥表皮毛一直被作為一種模式系統(tǒng)來研究細(xì)胞命運(yùn)決定、細(xì)胞周期調(diào)控、細(xì)胞極性以及細(xì)胞增大等細(xì)胞分化方面的問題。10目前對(duì)擬南芥表