拟南芥表皮毛发育机制

MolecularControlofArabidopsisTrichomesDevelopment姓名：王岩学号：2014051614生命学院遗传专业1Maincontent1.abstractabouttrichomesinArabidopsis2.theprocessoftrichomesdevelopment3.molecularcontrolofArabidopsistrichomesdevelopment4.conclusion21.Abstract:

InArabidopsis,trichomesaretypicallyunicellularstructuresandproducedonnearlyalltheaerialorgansexceptforthehypocotylandthecotyledons.Itsfunctionisprotectionagainstplant-eatinganimalsattack.Inthelasttwodecades,molecularmechanismsinvolvedintheinitiationanddevelopmentoftrichomeshavebeeninvestigatedwiththeobjectiveofanalyzingfactorscontrollingcellfateanddifferentiationinplantcells.Withtheavailabilityofalargenumberoftrichome-relatedmutantsinArabidopsis,manykeyregulatorscontrollingtrichomeformationhavebeenidentified.InArabidopsis,trichomesonrosetteleavesarelargesinglecells,usuallywiththreebranches,anduntilnowhavebeenthesubjectofresearch.342.发育过程建立在形态学标准基础上,拟南芥表皮毛发育分为6个阶段:阶段1:最开始,一个定向的表皮细胞相对于周围的表皮细胞快速膨胀(图1A),细胞核进行核内复制。表皮毛细胞之间大约相隔3-4个细胞阶段2:当表皮毛前期细胞扩展到比周围细胞直径大2–3倍时,开始出现垂直于表皮细胞层面的凸起,产生了表皮毛细胞的杆状结构(图1A)。阶段3:紧接着,正在生长的细胞顶端发育出细胞增大的共轭焦点,表皮毛分支开始发生(图1A)。拟南芥叶表皮毛根据地理品系一般会形成2–4个分支。分支的方向与叶片基部到顶部轴向相互对齐,且分支间的角度非常规则阶段4:在所有分支发生后,细胞通过弥散性生长继续增大,这样该细胞在直径和高度上就会有所增大。开始,正在生长的表皮毛分支是钝的(图1A)表皮毛细胞形态发生的不同发育阶段(每个细胞右下角的数字表示特定的发育阶段)5阶段5:顶端逐渐变尖(图1B)阶段6:在细胞增大停止后,表皮毛细胞表面形成数量不等的乳突(图1B),周围由1圈表皮支持细胞围绕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.结语：拟南芥表皮毛作为一种特化的、典型的单细胞表皮毛,其发育过程简单,在植物表面的分布有一定模式,其突变体不改变植物发育的其它性状而便于遗传分析,所以拟南芥表皮毛一直被作为一种模式系统来研究细胞命运决定、细胞周期调控、细胞极性以及细胞增大等细胞分化方面的问题。10目前对拟南芥表