Characterization of Negative Regulators of Arabidopsis Trichome Development

拟南芥叶片表面毛状体的发育被用作研究细胞命运和分化控制的模型。该模型具有基本属性和实用属性。了解多细胞生物中控制细胞命运和分化的基本机制是生物学研究的关键目标。考虑到控制细胞周期的机制在植物和非植物中是相似的，研究毛状体发育所获得的信息可能会导致更好地理解其他细胞类型是如何分化的。该模型具有实际意义，因为许多植物的毛状体是抵御恶劣环境因素的第一道防线。许多作物只有稀疏的毛发覆盖，从这项研究中获得的信息可能会导致改善作物植物的新策略。在野生型拟南芥中，叶片毛状体均匀分布在叶片表面；不到0.5%的毛状体彼此相邻生长。以前的分析表明，毛状体的间距不是由偶然控制的，而是由发育调节的间距程序控制的。这样的分析表明，间隔程序涉及细胞间的通信，防止邻近细胞成为毛状体。研究发现，毛状体起始所需的GL1基因在过表达时实际上抑制毛状体起始。这种抑制不是由于共抑制，因为已经发现35S::GL1植物过表达GL1 mRNA和蛋白。有人提出，GL1的过表达会导致叶片范围内的横向抑制程序的产生，在该程序中，邻近细胞相互抑制，不成为毛状体。为了验证这一假设，一项突变分析被用于鉴定能够抑制35S::GL1表型并增加叶片毛状体起始的突变。其中一个有趣的突变体，被称为cot，已经被广泛地描述。在35S::GL1 cot植物中，许多围绕毛状体的细胞进入毛状体通路。除了35S::GL1位点外，还发现了其他35S::GL1突变体可以抑制35S::GL1表型。这些新的突变体将被表征，最有趣的基因将被定位克隆。虽然最初的35S::GL1突变群体是从化学诱变的种子中分离出来的，但为了便于随后鉴定的突变基因的克隆，利用T-DNA标记诱导了一个新的35S::GL1突变群体。除上述研究外，另一个被假设为负调节因子的基因将被表征。这种被称为cpc样1 （CPL1）的基因在高水平表达时似乎也限制了毛状体的起始。预测CPL1的抑制机制与GL1过表达的抑制机制不同。这将受到考验。最后，将确定使用基因芯片的微阵列分析是否可以检测到在过表达GL1或CPL1的植物中差异表达的基因。

0091052MarksThe development of hairs, called trichomes, on the leaf surface of Arabidopsis plants is being used as a model to study the control of cell fate and differentiation. The model has both basic and practical attributes. Understanding the basic mechanisms that control cell fate and differentiation in multicellular organisms is a key goal in biological research. Given that the mechanisms that control the cell cycle are similar in plants and non-plants, it is possible that the information obtained in studying trichome development will lead to a better understanding of how other cell types differentiate. The model is of practical importance because the trichomes on many plants form the first line of defense againsthostile environmental factors. Many crop plants only have a sparse covering of hairs and the information obtained from this research could lead to new strategies to improve crop plants. In wild type Arabidopsis, leaf trichomes are uniformly spaced over the leaf surface; less than 0.5% of the trichomes develop adjacent to one another. Previous analyses have shown that trichome spacing is not controlled by chance but by a developmentally regulated spacing program. Such analyses indicate that the spacing program involves cell to cell communication that prevents neighboring cells from becoming trichomes.It has been found that the GL1 gene, which is required for trichome initiation, actually inhibits trichome initiation when overexpressed. This inhibition of initiation is not due to co-suppression, as it has been found that 35S::GL1 plants overexpress both GL1 mRNA and protein. It is proposed that overexpression of GL1 results in the production of a leaf-wide lateral inhibition program in which neighboring cells inhibit each other from becoming trichomes. To test this hypothesis, a mutational analysis is being used to identify mutations that can suppress the 35S::GL1 phenotype and increase leaf trichome initiation. One such interesting mutant, called cot, has been extensively characterized. In 35S::GL1 cot plants, many of the cells that surround a trichome enter the trichome pathway. In addition to35S::GL1 cot, other 35S::GL1 mutants have been identified that can suppress the 35S::GL1 phenotype. These new mutants will be characterized, and the most interesting genes will be targeted for positional cloning. Although the original 35S::GL1 mutant population was isolated from chemically mutagenized seed, to facilitate cloning of subsequently identified mutant genes, a new population of 35S::GL1 mutants is being induced by T-DNA tagging.In addition to the above studies, another gene hypothesized to be a negative regulator will be characterized. This gene, called CPC-like 1 (CPL1), also appears to limit trichome initiation when expressed at high levels. It is predicted that the CPL1 mechanism of inhibition is distinct from the mechanism resulting from GL1 overexpression. This will be tested. Finally, it will be determined if microarray analysis using gene chips can detect genes that are differentially expressed in plants overexpressing either GL1 or CPL1.