拟南芥表皮毛发育机制

1、1Molecular Control of Arabidopsis Trichomes Development 姓名：王岩 学号：2014051614 生命学院遗传专业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.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:阶段阶段1: 最开始最开始, 一个定向的表皮细胞相对于周围的表皮细胞快速一个定向的表皮细胞相对于周围的表皮细胞快速膨胀膨胀(图图1A),细胞核进行核内复制。表皮毛细胞之间大约相隔细胞核进行核内复制。表皮毛细胞之间大约相隔3-4个细胞个细胞阶段阶段2: 当表皮毛前期细胞扩展到比周围细胞直径大当表皮毛前期细胞扩展到比

5、周围细胞直径大23倍倍时时, 开始出现垂直于表皮细胞层面的凸起开始出现垂直于表皮细胞层面的凸起, 产生了表皮毛细产生了表皮毛细胞的杆状结构胞的杆状结构(图图1A)。阶段阶段3: 紧接着紧接着, 正在生长的细胞顶端发育出细胞增大的共正在生长的细胞顶端发育出细胞增大的共轭焦点轭焦点, 表皮毛分支开始发生表皮毛分支开始发生(图图1A)。拟南芥叶表皮毛根。拟南芥叶表皮毛根据地理品系一般会形成据地理品系一般会形成24个分支。分支的方向与叶片基个分支。分支的方向与叶片基部到顶部轴向相互对齐部到顶部轴向相互对齐, 且分支间的角度非常规则且分支间的角度非常规则阶段阶段4:在所有分支发生后在所有分支发生后, 细

6、胞通过弥散性生长继细胞通过弥散性生长继续增大续增大,这样该细胞在直径和高度上就会有所增大。这样该细胞在直径和高度上就会有所增大。开始开始, 正在生长的表皮毛分支是钝的正在生长的表皮毛分支是钝的(图图1A)表皮毛细胞形态发生的不同发育阶段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每个细胞右下角的数字表示特定的发育阶段)6阶段阶段5: 顶端逐渐变尖顶端逐渐变尖(图图1B)阶段阶段6: 在细胞增大停止后在细胞增大停止后, 表皮毛细胞表面表皮毛细胞表面 形成数量不等的乳突形成数量不等的乳突(图图1B), 周围由周围由1圈表皮圈表皮支持细胞围绕支持细胞围绕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.结语：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