Ionic and Cytoskeletal Control of Developmental Polarity in a Plant Zygote

本研究将研究褐藻Pelvetia受精卵的细胞骨架和极性离子碱基。本提案的前提是极性的获得是细胞高度调控的重组，通过研究关键调控过程之间的关系可以更好地理解这一点。Kropf博士将研究细胞骨架对极性的控制，然后研究细胞骨架和胞浆调节离子之间的关系。初步证据表明，皮质f -肌动蛋白在受精后不久定位于一个斑块，并扩展成一个环，预示着未来的根状部位。Kropf博士假设精子的进入诱导了局部的f -肌动蛋白聚合，然后作为极性的决定因素，特别是标记未来的根状位点。这一假设将通过冷冻固定、共聚焦显微镜和透射电镜进行检验。在有丝分裂之前，细胞核旋转90度，使中心体呈轴向排列。这个核旋转决定了主轴的轴向方向和第一分割平面的横向对齐。微管被认为是核旋转的主要原因，它们在旋转过程中的动态行为将通过向受精卵注射荧光标记的微管蛋白来实时研究。中心体的组装和功能也将被研究。最后，将研究细胞骨架元件的组装和功能受局部离子活性（特别是H+和CA+2活性）调节的假设。＊＊＊

9506094 Kropf The research described in this proposal will investigate the cytoskeletal and ionic bases of polarity in zygotes of the brown alga Pelvetia. The premise in this proposal is that the acquisition of polarity is a highly regulated reorganization of the cell which will be best understood by investigating relationships between key regulatory processes. Dr. Kropf will study cytoskeletal control of polarity, and then investigate the relationship between the cytoskeleton and cytosolic regulatory ions. Preliminary evidence indicates that cortical F-actin localizes in a patch soon after fertilization, and expands into a ring that portends the future rhizoid site. Dr. Kropf hypothesizes that sperm entry induces local F-actin polymerization that then serves as a determinant of polarity, specifically marking the future rhizoid site. This hypothesis will be examined using cryofixation, confocal microscopy and TEM. Prior to mitosis, the nucleus rotates 90 degrees bringing centrosomes into an axial alignment. This nuclear rotation determines the axial orientation of the spindle and transverse alignment of the first division plane. Microtubules are thought to be primarily responsible for nuclear rotation, and their dynamic behavior during rotation will be investigated in real time by injecting zygotes with fluorescently tagged tubulin. Centrosome assembly and function will also be investigated. Finally the hypothesis that the assembly and function of cytoskeletal elements are regulated by local ion activities, specifically H+ and CA+2 activities, will be investigated. ***