Rho GTPases in Plant Development: A Genetic and Cell Biological Analysis

0111078福勒因为植物细胞是固定的，并通过细胞壁固定在组织内，它们的形状和大小（形态学）必须通过精确调节细胞扩张的位点和/或细胞分裂的平面来产生。 目前的数据表明，扩张和分裂的调节取决于与细胞皮层，质膜和细胞壁相关的因素之间的相互作用。 然而，对这些因子（蛋白质和信号）及其在植物细胞形态发生中的功能的机械理解是不完整的。 有证据表明，Rho GTPases的植物特异性Rop亚家族参与调节细胞皮层的这些形态发生过程，包括花粉管生长、肌动蛋白细胞骨架的分布和细胞壁合成。 然而，在整个植物生长和发育过程中特定Rop的体内功能知之甚少。已经分离出大量的突变在五个rop基因，和突变表型的评估表明，至少有一个这些rop基因，ropB，在花粉管中的功能。 私家侦探将采取遗传，分子和细胞生物学相结合的方法来了解Rop家族在植物发育中的功能。 特别是私家侦探将通过详细表征ropB突变体表型来确定玉米ROPB的体内功能。 将分析来自单和双rop突变体植物的突变体花粉管在玉米花柱（丝）中的生长。 将在具有多种抑制剂的培养物中测试突变的花粉管，以剖析ROPB下游的信号传导途径。 私家侦探还将产生和表征表达植物细胞骨架荧光报告基因的玉米植物，并使用这些基因更精确地剖析rop突变对体内细胞骨架分布的影响。这项工作将深入了解这些重要的信号分子，并有助于澄清它们在几个过程中的作用（例如，授粉和花粉管生长，细胞壁合成）。 除了有助于基础科学知识，我们的研究结果可能会提出操纵特定作物的方法，从而改善作物。 单子叶植物玉米与其他重要的禾本科作物（水稻、小麦）的密切关系表明，

0111078FowlerBecause plant cells are immobile, and are fixed within tissues by a cell wall, their shapes and sizes (morphology) must be generated by precise regulation of the sites of cell expansion and/or the planes of cell division. Current data indicate that regulation of expansion and division depends on interactions among factors associated with the cell cortex, the plasma membrane and the cell wall. However, a mechanistic understanding of these factors (proteins and signals) and their functions in plant cell morphogenesis is incomplete. Evidence is building that the plant-specific Rop subfamily of the Rho GTPases is involved in regulating these morphogenetic processes at the cell cortex, including pollen tube growth, the distribution of the actin cytoskeleton, and cell wall synthesis. However, the in vivo functions of specific Rops throughout plant growth and development are poorly understood.Using the model crop plant Zea mays, the P.I. has isolated a large collection of mutations in five rop genes, and evaluation of mutant phenotypes indicates that at least one of these rop genes, ropB, functions in the pollen tube. The P.I. will take a combined genetic, molecular, and cell biological approach to understanding the functions of the Rop family in plant development. Specifically, the P.I. will determine the in vivo functions of maize ROPB by a detailed characterization of the ropB mutant phenotype. Growth in the maize style (the silk) of mutant pollen tubes from single and double rop mutant plants will be analyzed. Mutant pollen tubes will be tested in culture with a variety of inhibitors, to dissect the signaling pathways downstream of ROPB. The P.I. will also generate and characterize maize plants expressing fluorescent reporters of the plant cytoskeleton, and use these to more precisely dissect the effects of rop mutations on cytoskeletal distribution in vivo.This work will provide insight into these important signaling molecules, and should help clarify their roles in several processes (e.g., pollination and pollen tube growth, cell wall synthesis). In addition to contributing to basic scientific knowledge, our results may suggest ways to manipulate specific rops that would lead to crop improvement. The close relationship of the monocot Zea mays to other important grass crops (rice, wheat) suggests