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

所有细胞都是从现有细胞中产生的。在所有生物体中，内容物的加倍和将这些内容物分配给子细胞必须小心控制。Septin蛋白家族在组织芽殖酵母酿酒酵母的适当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复合物似乎起到支架的作用，将其他蛋白质招募和束缚到适当的位点。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似乎协调生长与核分裂的细胞周期调节剂。除了酿酒酵母外，还在多细胞真菌和动物中发现了septins。已在丝状真菌构巢曲霉（Aspergillusnidulans）中鉴定出5个septin基因，即aspA-aspE。在这种多细胞真菌中，单个隔蛋白AspBp定位于几个不同的结构（隔膜，分支和分生孢子）。AspBp定位于有丝分裂后的隔膜，在隔膜发育期间，定位模式从单环变为双环再变为单环。AspBp定位于有丝分裂前的分枝，随着分枝的出现，定位模式从紧密的斑块变为弥散的领状。巢多糖含有septin和非septin蛋白质的不同组合，并且随着发育的进行，同一复合物内的成员将随时间而变化。这一假设将使用各种方法进行检验。 将检查所有5种septins的突变表型和定位。 将使用遗传和生物化学方法鉴定septins之间以及septins与其他蛋白质之间的相互作用。 将定位与隔膜处的隔膜蛋白复合物相互作用的选定非隔膜蛋白。 这些研究将开发出预测和操纵隔发育的能力，以及在较小程度上预测和操纵A. nidulans。拟议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.