Developmental Polarity in Fucoid Zygotes

岩藻样受精卵的发育极性

• 批准号: 0110113
• 负责人: Darryl Kropf
• 金额: $ 39万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2005-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0110113&HistoricalAwards=false
• 关键词: Developmental; Polarity; Fucoid; Zygotes

0110113KropfZygotes (fertilized eggs) of fucoid brown algae are ideal for investigating the mechanisms that establish polarity in developing organisms. Dr. Kropf's lab has for some time been investigating the cellular and physiological mechanisms that establish a growth axis and determine the division plane in these zygotes. From this work they have formulated hypotheses to be tested during this award period. The working hypotheses are as follows:Growth axis specification. Dr. Kropf proposes that polarity is first set in place at fertilization with the site of sperm entry specifying the rhizoid pole of the growth axis. This site is marked by local assembly of a cytoskeletal element, F-actin. The fertilized egg then settles onto the rocks in the intertidal zone, attaches and begins to monitor its environment for spatial information to help determine the direction of the rocky substratum. If relevant vectors are perceived, the sperm-induced axis is abandoned and a new axis is generated such the new rhizoid pole is toward the rock surface. Concomitantly, the actin patch at the sperm entry site is disassembled and a new patch is assembled at the nascent rhizoid site. Realignment of the axis can occur repeatedly over several hours. Finally, about 12 hours after fertilization, growth ensues at the current rhizoid pole; the rhizoid formed attaches the zygote firmly to rocks and eventually forms the holdfast of the alga.Division plane alignment. Dr. Kropf speculates that division plane is determined at telophase of mitosis such that the new cell wall is deposited transverse to the axis defined by the two telophase nuclei. The orientation of the telophase nuclei is determined by centrosomal position. Centrosomes are inherited paternally and separate to opposite sides of the zygotic nucleus. Initially, the axis defined by the two centrosomes is randomly aligned with the growth axis, but prior to cytokinesis the centrosomal axis becomes aligned with the growth axis by a combination of nuclear rotation and spindle elongation. Research in this proposal will test and extend the most important aspects of the models. The primary objectives are to 1) investigate the requirement for dynamic actin in specifying the growth axis, 2) identify actin nucleating molecules, 3) determine the role of asymmetric cell shape in division plane alignment, 4) assess whether telophase spindle position determines division plane, and 5) investigate the role of microtubules in defining the division plane.

0110113岩藻合子(受精卵)是研究在发育中的生物体中建立极性的机制的理想方法。Kropf博士的实验室一段时间以来一直在研究在这些受精卵中建立生长轴和确定分裂平面的细胞和生理机制。从这项工作中，他们制定了在这一获奖期内要检验的假设。工作假设如下：生长轴规范。Kropf博士建议，在受精时首先设定极性，精子进入的位置指定生长轴的根状极。这个部位的标志是细胞骨架元件F-肌动蛋白的局部组装。然后，受精卵定居在潮间带的岩石上，附着并开始监测其环境，以获得空间信息，以帮助确定岩石底层的方向。如果感知到相关的载体，精子诱导轴就会被放弃，并产生一个新的轴，这样新的类根极点就会朝向岩石表面。同时，精子进入部位的肌动蛋白斑块被分解，而在新生的类根部位组装了一个新的斑块。轴的重新对齐可能会在几个小时内重复进行。最后，在受精后约12小时，在当前的拟根极生长，形成的拟根将受精卵牢固地附着在岩石上，最终形成藻类的固定物。Kropf博士推测，分裂平面是在有丝分裂的末期确定的，因此新的细胞壁横跨由两个末期核确定的轴沉积。末期核的取向由中心体的位置决定。中心体是父系遗传的，并分离到合子核的两边。最初，由两个中心体定义的轴与生长轴随机对齐，但在胞质分裂之前，中心体轴通过核旋转和纺锤体伸长的组合与生长轴对齐。这项提案中的研究将测试和扩展模型的最重要方面。主要目的是1)研究动态肌动蛋白在指定生长轴中的需求，2)鉴定肌动蛋白成核分子，3)确定细胞形状不对称在分裂平面排列中的作用，4)评估端粒纺锤体的位置是否决定分裂平面，以及5)研究微管在定义分裂平面中的作用。