CAREER: Molecular Mechanisms of Plant Cell Tip Growth

研究活动：尖端生长是植物细胞生长的一种形式，虽然仅限于几种细胞类型，但对于从藻类到开花植物等植物物种的发育是必不可少的。特别是在种子植物中，顶端生长的花粉管是受精所必需的，因此是物种繁殖所必需的。根毛对整个植物生长发育所需的水分和矿物质的吸收非常重要。这个项目将专注于破译控制尖端生长的分子信号，从而影响到进化上广泛的植物细胞发育。这项研究将在一种新兴的植物模式系统--苔藓Physcomitrella patens中进行。分子遗传操作的简便性和尖端生长细胞的丰富使苔藓成为这些研究的理想选择。苔藓系统在植物中是独一无二的，因为它具有基因靶向的能力。此外，贝扎尼拉博士最近开发了一种快速的RNA干扰分析，它可以迅速揭示植物基因的功能，在任何植物系统中都是无与伦比的。使用这种分析方法，贝扎尼拉博士发现，参与肌动蛋白细胞骨架网络的某些蛋白质对TIP的生长至关重要。这些研究产生了一个工作模型，在该模型中，生长极化由植物特有的小GTP酶ROP的激活引起的分子信号级联控制，该分子信号级联反过来通过Forins(肌动蛋白细丝的细胞核仁)向肌动蛋白单体结合蛋白Profilin发出信号，从而协调生长部位发生的肌动蛋白动态。该项目将使用反向遗传学、动态活细胞成像和分子相互作用屏幕的组合来测试这个模型。将解决三个主要问题：(1)ROP是如何调节的？(2)福尔马林在ROP-Profilin途径中起作用吗？以及(3)ROP-Profilin途径的分子组成是什么？许多生物，包括真菌和动物，通过类似的信号级联来控制细胞的形态发生。因此，这项研究将为这一进化保守的过程提供新的比较洞察力。更广泛的影响：该项目具有潜在的农业社会效益。通过阐明控制植物细胞顶端生长的基本机制，这项研究将影响对重要植物细胞类型的理解，这些类型涉及决定植物整体适合性，从而决定作物产量。该项目还将把研究与教学和培训结合起来，并将扩大未被充分代表的群体对科学的参与。贝扎尼拉博士本身就是科学界代表性不足的少数族裔的一员，她招募并指导了一名优秀的少数族裔博士后研究员。贝扎尼拉博士还将开发一门关于MOSS方法的课程，通过NSF资助的东北研究生教育联盟和教授，在马萨诸塞大学以及合作的少数族裔服务机构教授这门课程，以进一步加强对科学领域代表性不足群体的招聘。

Research Activity: Tip growth is a form of plant cell growth that although restricted to a few cell types, is essential for the development of plant species ranging from algae to flowering plants. In seed plants in particular, the tip-growing pollen tube is required for fertilization and thus propagation of the species. The root hair is important for absorption of water and minerals required for growth and development of the entire plant. This project will focus on deciphering the molecular signals that control tip growth, thus impacting an evolutionarily wide range of plant cell development. The research will be carried out in an emerging plant model system, the moss Physcomitrella patens. The ease of molecular genetic manipulation and the abundance of tip growing cells make moss ideal for these studies. The moss system is unique among plants for its gene-targeting capabilities. Additionally Dr. Bezanilla recently developed a rapid RNA interference assay, which rapidly reveals plant gene function and is unparalleled in any plant system. Using this assay, Dr. Bezanilla found that certain proteins participating in the actin cytoskeletal network are critical for tip growth. These studies have lead to a working model whereby growth polarization is controlled by a molecular signaling cascade stemming from activation of the plant-specific small GTPase ROP, which in turn signals to the actin monomer binding protein profilin via formins, cellular nucleators of actin filaments, thus coordinating actin dynamics to occur at the site of growth. The project will test this model using a combination of reverse genetics, dynamic live-cell imaging, and molecular interaction screens. Three major questions will be addressed: (1) How is ROP regulated? (2) Do formins function in the ROP-profilin pathway? and (3) What is the molecular composition of the ROP-profilin pathway? Many organisms, including fungi and animals, control cellular morphogenesis via a similar signaling cascade. Thus this research will provide novel comparative insights into this evolutionarily conserved process.Broader Impacts: This project has potential agricultural benefits for society. By elucidating the fundamental mechanisms controlling plant cell tip growth, this research will impact the understanding of important plant cell types, which are involved in determining overall plant fitness and thus crop yields. The project will also integrate research with teaching and training and will broaden the participation of underrepresented groups in science. Dr. Bezanilla, herself a member of an underrepresented minority in science, has recruited and mentored an excellent minority postdoctoral researcher. Dr. Bezanilla will also develop a course on moss methods that will be taught both at the University of Massachusetts as well as at partner minority serving institutions through an NSF-funded Northeast Alliance for Graduate Education and the Professoriate to further enhance recruitment of underrepresented groups in science.