1、1Molecular Control of Arabidopsis Trichomes Development 姓名：王巖 學號：2014051614 生命學院遺傳專業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.發育過程建立在形態學標準基礎上, 擬南芥表皮毛發育分為6個階段:階段階段1: 最開始最開始, 一個定向的表皮細胞相對于周圍的表皮細胞快速一個定向的表皮細胞相對于周圍的表皮細胞快速膨脹膨脹(圖圖1A),細胞核進行核內復制。表皮毛細胞之間大約相隔細胞核進行核內復制。表皮毛細胞之間大約相隔3-4個細胞個細胞階段階段2: 當表皮毛前期細胞擴展到比周圍細胞直徑大當表皮毛前期細胞擴展到比

5、周圍細胞直徑大23倍倍時時, 開始出現垂直于表皮細胞層面的凸起開始出現垂直于表皮細胞層面的凸起, 產生了表皮毛細產生了表皮毛細胞的桿狀結構胞的桿狀結構(圖圖1A)。階段階段3: 緊接著緊接著, 正在生長的細胞頂端發育出細胞增大的共正在生長的細胞頂端發育出細胞增大的共軛焦點軛焦點, 表皮毛分支開始發生表皮毛分支開始發生(圖圖1A)。擬南芥葉表皮毛根。擬南芥葉表皮毛根據地理品系一般會形成據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則且分支間的角度非常規則階段階段4:在所有分支發生后在所有分支發生后, 細

6、胞通過彌散性生長繼細胞通過彌散性生長繼續增大續增大,這樣該細胞在直徑和高度上就會有所增大。這樣該細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)表皮毛細胞形態發生的不同發育階段表皮毛細胞形態發生的不同發育階段(每個細胞右下角的數字表示特定的發育階段每個細胞右下角的數字表示特定的發育階段)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: 在細胞增大停止后在細胞增大停止后, 表皮毛細胞表面表皮毛細胞表面 形成數量不等的乳突形成數量不等的乳突(圖圖1B), 周圍由周圍由1圈表皮圈表皮支持細胞圍繞支持細胞圍繞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.結語：結語： 擬南芥表皮毛作為一種特化的、典型的單細胞表皮毛,其發育過程簡單, 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來研究細胞命運決定、細胞周期調控、細胞極性以及細胞增大等細胞