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

所有的细胞都是由现有的细胞产生的。在所有生物体中，内容物的加倍和这些内容物向子细胞的分裂都必须仔细控制。septin家族蛋白在组织芽殖酵母酿酒酵母的正常生长和分裂中起着核心作用，并且可能在许多其他真核生物中起着类似的作用。Septin复合物似乎起着支架的作用，招募并将其他蛋白质拴在合适的位置。在以septin依赖的方式定位于酵母分裂平面的蛋白质中，有负责跨壁合成的酶和细胞周期调节因子，它们似乎与核分裂协调生长。虽然大多数关于septin功能的知识来自于对单细胞真菌酿酒酵母的研究，但在多细胞真菌和动物中也发现了septin。在线状真菌细粒曲霉中鉴定出5个septin基因，分别为aspA-aspE。在这种多细胞真菌中，一个单独的间隔蛋白AspBp定位于几个不同的结构（间隔、分支和分生孢子）。AspBp定位发生在间隔有丝分裂后，定位模式在间隔发育过程中从单环变为双环再变为单环。AspBp的定位发生在分支有丝分裂前，随着分支的出现，定位模式从紧凑的斑块转变为弥散的环状。本研究的中心假设是，针叶芽孢杆菌的间隔、新生分支和分生孢子的复合体含有间隔蛋白和非间隔蛋白的不同组合，并且随着发育的进行，同一复合体的成员将随着时间的推移而变化。这一假设将使用多种方法进行检验。突变表型和定位将检查所有五个septin。septin之间的相互作用以及septin与其他蛋白质之间的相互作用将通过遗传和生化方法进行鉴定。选定的非间隔蛋白与间隔蛋白复合物在间隔处相互作用将被定位。这些研究将利用预测和操纵中隔的能力，以及在较小程度上其他结构的发展，在a . nidulans。所提出的研究可能会导致更好地了解septin在多细胞生物中的功能和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.