Regulation of the Orientation of Cell Expansion in Plants

该项目的长期目标是了解调节细胞扩增方向的分子机制。植物器官的形状在很大程度上取决于细胞在特定方向上直接扩张的能力。棉花等农产品的质量取决于高度定向的细胞扩增。一项对拟南芥根系细胞扩增的遗传分析已经鉴定出具有异常定向扩增的突变体。特别令人感兴趣的是眼镜蛇突变，它导致细胞呈放射状而不是纵向扩张。对眼镜蛇表型的详细分析导致了眼镜蛇基因产物调节从径向向纵向扩张的转变的假设。已对COBRA基因进行了定位克隆，其氨基酸序列推断表明COBRA蛋白锚定在质膜上，并且该蛋白的一部分可以与细胞壁相互作用。COBRA活性在转录水平受到调节的证据来自于发现，在根细胞中，COB RNA的水平在经历从径向向纵向扩张的转变时增加。本提案的目的是验证COBRA是定向细胞扩增调节剂的假设，并使用COBRA来表征定向细胞扩增被控制的分子机制。这将通过确定COBRA RNA和蛋白质的正常表达和定位以及分析改变这些表达模式的影响来完成。然后，COBRA将被用作起点，以建立对调节定向细胞扩增的分子相互作用的理解。

The long term goal of this project is to understand the molecular mechanisms that regulate the orientation of cell expansion. The shape of plant organs depends heavily on the ability of cells to direct expansion in specific orientations. The quality of agricultural products such as cotton is dependent on highly oriented cell expansion. A genetic analysis of cell expansion in the root of Arabidopsis has identified mutants with abnormally oriented expansion. Of particular interest is the cobra mutation which results in cells that appear to expand radially rather than longitudinally. A detailed analysis of the cobra phenotype led to the hypothesis that the COBRA gene product regulates the transition from radial to longitudinal expansion. The COBRA gene has been positionally cloned and its deduced amino acid sequence indicates that the COBRA protein is anchored to the plasma membrane and that a portion of the protein could interact with the cell wall. Evidence that COBRA activity is regulated at the transcriptional level comes from the finding that there are increased levels of COB RNA in root cells that are undergoing the transition from radial to longitudinal expansion. The goal of this proposal is to test the hypothesis that COBRA is a regulator of oriented cell expansion and to use COBRA to characterize the molecular mechanisms by which oriented cell expansion is controlled. This will be done by determining the normal expression and localization of COBRA RNA and protein and by analyzing the effects of altering these expression patterns. COBRA will then be used as the starting point to build an understanding of the molecular interactions that regulate oriented cell expansion.