Septins in Aspergillus nidulans: Organization of the Division Site and the Cell Surface

所有细胞都是从现有细胞产生的。在所有生物体中，必须仔细控制内容物的加倍和这些内容物到子代细胞的分割。Septin蛋白家族在酿酒酵母芽生组织的正常生长和分裂中起着核心作用，在许多其他真核生物中也可能发挥类似的作用。Septin复合体似乎起到了支架的作用，招募其他蛋白质并将其连接到适当的位置。在依赖于Septin的方式定位于酵母分裂平面的蛋白质中，有一些负责跨壁合成和细胞周期调节的酶，它们似乎协调着生长和核分裂。虽然大多数关于Septin功能的知识来自于单细胞真菌S.cerevisiae的出色工作，但Septins也在多细胞真菌和动物中被发现。在丝状真菌Nidulans中已鉴定出5个Septin基因，ASPA-Aspe。在这种多细胞真菌中，一个单一的分离素AspBp定位于几个不同的结构(隔膜、分枝和分生孢子梗)。AspBp定位是隔膜有丝分裂后的定位，在隔膜发育过程中定位模式从单环到双环再到单环。AspBp定位在分枝上是有丝分裂前的，随着分枝的出现，定位模式从紧凑的斑块转变为扩散的项圈。本研究的中心假设是，多核拟青霉的隔膜、新生分枝和分生孢子梗的复合体含有不同的Septin和非Septin蛋白质的组合，并且随着发育的进行，同一复合体中的成员会随着时间的推移而变化。这一假设将使用各种方法进行检验。将检查所有五种Septin的突变表型和定位。将使用遗传和生物化学方法确定Septins之间的相互作用以及Septins与其他蛋白质之间的相互作用。选定的与SEPTA上的Septin复合体相互作用的非Septin蛋白将被定位。这些研究将利用预测和操纵隔膜发育的能力，以及在较小程度上其他结构的能力。拟议的研究可能有助于更好地理解多细胞生物体中的分隔素功能，以及丝状真菌发育的基本过程。

All cells arise from existing cells. The doubling of contents and partitioning of those contents to daughter cells must be carefully controlled in all organisms. The septin family of proteins plays a central role in organizing proper growth and division of the budding yeast Saccharomyces cerevisiae and likely plays a similar role in many other eukaryotes. Septin complexes appear to function as scaffolds, recruiting and tethering other proteins to appropriate sites. Among the proteins that localize to the yeast division plane in a septin-dependent manner are enzymes responsible for cross-wall synthesis and cell cycle regulators that appear to coordinate growth with nuclear division.While most knowledge of septin function comes from elegant work in the unicellular fungus S. cerevisiae, septins have also been found in multicellular fungi and in animals. Five septin genes, aspA-aspE, have been identified in the filamentous fungus Aspergillus nidulans. In this multicellular fungus a single septin, AspBp, localizes to several different structures (septa, branches, and conidiophores). AspBp localization is post-mitotic at septa where the localization pattern changes from a single ring to a double ring back to a single ring during septal development. AspBp localization is pre-mitotic at branches where the localization pattern changes from a compact patch to a diffuse collar as branches emerge.The central hypothesis for this research is that complexes at septa, nascent branches, and conidiophores in A. nidulans contain different combinations of both septin and non-septin proteins and that membership within the same complex will vary over time as development proceeds. This hypothesis will be tested using a variety of approaches. Mutant phenotypes and localization will be examined for all five septins. Interactions among septins and between septins and other proteins will be identified using genetic and biochemical methods. Selected non-septin proteins that interact with septin complexes at septa will be localized. These studies will exploit the ability to predict and manipulate the development of septa, and to a lesser extent other structures, in A. nidulans. The proposed studies will likely lead to a better understanding of septin function in multicellular organisms and of basic processes in the development of filamentous fungi.