Regulation of spindle microtubule organization in plants

细胞生物通过细胞分裂产生新的细胞来繁殖。当真核细胞分裂时，它们产生纺锤体，确保遗传物质忠实地分离成两个子细胞。这种生物机械是由微管的细胞骨架丝组装而成的。在真菌和动物等生物体中，纺锤体的两极通常由两个中心体定义。然而，在进化过程中，中心体不再在开花植物中产生。然而，这些缺乏这种结构的纺锤体仍然可以准确地行使它们在细胞分裂中的基本功能。这项研究旨在了解调节植物纺锤体微管阵列形成的蛋白质的作用。从植物纺锤体组装中学到的知识也将阐明细胞分裂是如何在其他生物体中进行的。这项工作将涉及本科生和研究生的参与。高中生也将有机会在暑期参与这项研究。本项目旨在通过使用两个模型系统来了解植物中无着丝体纺锤体微管组织的调控机制，即有中心体存在但并不总是用于有丝分裂的多形地钱草和没有中心体结构的开花植物拟南芥。在拟南芥中的初步研究集中在极光有丝分裂激酶(αAur)及其调节子TPXL3、微管蛋白环复合体的微管核蛋白(GammaTuRC)以及与纺锤体MTS相关的ATK1和ATK5的Kinesin-14马达。当这些蛋白质的功能受损时，纺锤体不能建立收敛极，最终突变植株在营养生长和繁殖方面都表现出严重的缺陷。工作假说是，αAur调节GammaTuRC和Kinesin-14在纺锤体组装中的功能。具体地说，有丝分裂纺锤体的形成需要依赖于Kinesin-14的微管组织和GammaTuRC的极向积累。这一假说将通过1)成像技术来确定纺锤体微管组织在有丝分裂过程中的基本调节作用；2)遗传工具来分析目标蛋白的功能；以及3)生物化学方法来了解它们的功能是如何调节的。从这些研究中获得的体外和体内结果将有助于阐明调节无着丝体纺锤体组装的机制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Cellular organisms propagate by producing new cells through cell division. When eukaryotic cells divide, they generate the spindle apparatus that ensures the faithful segregation of the genetic material into two daughter cells. This biological machinery is assembled by the cytoskeletal filaments of microtubules. Spindles often have their poles defined by two centrosomes in organisms like fungi and animals. During evolution, however, the centrosome is no longer produced in flowering plants. Yet these spindles lacking this structure can still precisely exercise their essential function in cell division. This research is aimed at understanding the roles of proteins that regulate the formation of the spindle microtubule array in plants. The knowledge learned from spindle assembly in plants also will illuminate how cell division is executed in other organisms. The work will involve the participation of both undergraduate and graduate students. High school students will also have an opportunity to participate in the research during the summers. This project aims to understand mechanisms that regulate acentrosomal spindle microtubule organization in plants by employing two model systems, the basal liverwort Marchantia polymorpha in which the centrosome is present but not always used in mitosis and the flowering plant Arabidopsis thaliana that lacks the structure. Preliminary studies in A. thaliana were focused on the mitotic kinase of Aurora (alphaAur) and its regulator TPXL3, the microtubule nucleator of the gamma-tubulin ring complex (gammaTuRC), and the Kinesin-14 motors of ATK1 and ATK5 that are associated with spindle MTs. When functions of these proteins were compromised, spindles failed to establish convergent poles, and ultimately mutant plants showed severe defects in both vegetative growth and reproduction. The working hypothesis is that alphaAur regulates the functions of gammaTuRC and Kinesin-14 in spindle assembly. Specifically, the formation of mitotic spindles with convergent poles requires Kinesin-14-dependent microtubule organization and poleward accumulation of gammaTuRC. This hypothesis will be tested by employing 1) imaging techniques to determine the actions of essential regulators of spindle microtubule organization during mitosis; 2) genetic tools to dissect functions of targeted proteins; and 3) biochemical methods to learn how their functions are regulated. In vitro and in vivo results garnered from these studies will contribute toelucidating mechanisms that regulate acentrosomal spindle assembly.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.