1、1Molecular Control of Arabidopsis Trichomes Development 姓名：王巖 學(xué)號：2014051614 生命學(xué)院遺傳專業(yè)2Main content 1. abstract about trichomes in Arabidopsis 2. the process of trichomes development 3. molecular control of Arabidopsis trichomes development 4. conclusion31. Abstract: In Arabidopsis, trichomes are typi

2、cally unicellular structures and produced on nearly all the aerial organs except for the hypocotyl and the cotyledons. Its function is protection against plant-eating animals attack. In the last two decades, molecular mechanisms involved in the initiation and development of trichomes have been inves

3、tigated with the objective of analyzing factors controlling cell fate and differentiation in plant cells. With the availability of a large number of trichome-related mutants in Arabidopsis, many key regulators controlling trichome formation have been identified. In Arabidopsis, trichomes on rosette

4、leaves are large single cells,usually with three branches, and until now have been the subject of research.452.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個階段:階段階段1: 最開始最開始, 一個定向的表皮細(xì)胞相對于周圍的表皮細(xì)胞快速一個定向的表皮細(xì)胞相對于周圍的表皮細(xì)胞快速膨脹膨脹(圖圖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個細(xì)胞個細(xì)胞階段階段2: 當(dāng)表皮毛前期細(xì)胞擴(kuò)展到比周圍細(xì)胞直徑大當(dāng)表皮毛前期細(xì)胞擴(kuò)展到比

5、周圍細(xì)胞直徑大23倍倍時時, 開始出現(xiàn)垂直于表皮細(xì)胞層面的凸起開始出現(xiàn)垂直于表皮細(xì)胞層面的凸起, 產(chǎn)生了表皮毛細(xì)產(chǎn)生了表皮毛細(xì)胞的桿狀結(jié)構(gòu)胞的桿狀結(jié)構(gòu)(圖圖1A)。階段階段3: 緊接著緊接著, 正在生長的細(xì)胞頂端發(fā)育出細(xì)胞增大的共正在生長的細(xì)胞頂端發(fā)育出細(xì)胞增大的共軛焦點(diǎn)軛焦點(diǎn), 表皮毛分支開始發(fā)生表皮毛分支開始發(fā)生(圖圖1A)。擬南芥葉表皮毛根。擬南芥葉表皮毛根據(jù)地理品系一般會形成據(jù)地理品系一般會形成24個分支。分支的方向與葉片基個分支。分支的方向與葉片基部到頂部軸向相互對齊部到頂部軸向相互對齊, 且分支間的角度非常規(guī)則且分支間的角度非常規(guī)則階段階段4:在所有分支發(fā)生后在所有分支發(fā)生后, 細(xì)

6、胞通過彌散性生長繼細(xì)胞通過彌散性生長繼續(xù)增大續(xù)增大,這樣該細(xì)胞在直徑和高度上就會有所增大。這樣該細(xì)胞在直徑和高度上就會有所增大。開始開始, 正在生長的表皮毛分支是鈍的正在生長的表皮毛分支是鈍的(圖圖1A)表皮毛細(xì)胞形態(tài)發(fā)生的不同發(fā)育階段表皮毛細(xì)胞形態(tài)發(fā)生的不同發(fā)育階段(每個細(xì)胞右下角的數(shù)字表示特定的發(fā)育階段每個細(xì)胞右下角的數(shù)字表示特定的發(fā)育階段)6階段階段5: 頂端逐漸變尖頂端逐漸變尖(圖圖1B)階段階段6: 在細(xì)胞增大停止后在細(xì)胞增大停止后, 表皮毛細(xì)胞表面表皮毛細(xì)胞表面 形成數(shù)量不等的乳突形成數(shù)量不等的乳突(圖圖1B), 周圍由周圍由1圈表皮圈表皮支持細(xì)胞圍繞支持細(xì)胞圍繞73. Arabi

7、dopsis trichomes: a model of trichome development and regulationthe activatorinhibitor mechanism: Initial epidermal cells equivalently express trichome-promoting factors, which can activate repressors but result in different cell fate in the neighboring cells. Numerous trichome-related mutants have

8、enabled theidentification of many trichome patterning genes, which can be divided into two types:trichome-positive and trichome-negative regulators. In Arabidopsis, one regulatory models have been identified in trichome formation that is the activatorinhibitor model.81) The positive regulators inclu

9、de the R2R3 MYB transcription factor GL1, the bHLH factor GL3 and the WD40- factorTTG1. GL1 and TTG1 interact withGL3, forming a MYB/bHLH/WD complex. This regulatory complex stimulates epidermal cells to differentiate into trichomes by activating the expression of its downstream activators GL2 and T

10、TG2. whichencodes a homeodomain-leucine zipper(HD-Zip) and a WRKY transcription factor individually. 2) The negative regulators are represented by six redundantly acting genes:CPC, TRY, ETC1, ETC2, ETC3 and TCL1. All of which encode single repeat R3 MYB proteins.9 These smallsized inhibitors can mov

11、e laterally into neighboring cells and compete with GL1 for binding toGL3,forming an inactivating complex, which cannot promote GL2 and TTG2 expression, thereby inhibiting trichome fate.3) It was reported that GL1 and GL3 contain a DNA-binding domain, respectively, and deletion of the DNA-binding do

12、mains completely represses the expression of their downstream gene GL2, suggesting that GL2 may be positively regulated by them through DNAprotein binding. Thereafter, it was suggested that GL1 directly binds to the promoters of GL2, which corresponds to the finding that TTG2 is directly regulated b

13、y GL1. Simultaneously,both TTG1 and GL3 were demonstrated to interact with the promoters of TTG2.10 TTG1 can directly activate the GL3/GL1 transcription,indicating that TTG1 may act upstream of GL3 and GL1. Moreover, GL3 was found to bind to its own promoter and an auto-inhibition was shown for this gene using co-transfection assays in protoplasts. These findings further our understanding of the activatorinhibitor mechanism of trichome formation.4.結(jié)語：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