Hernández-Rodríguez Yainitza, Masuo Shunsuke, Johnson Darryl, Orlando Ron, Smith Amy, Couto-Rodriguez Mara, Momany Michelle
Department of Plant Biology, University of Georgia, Athens, Georgia, United States of America.
Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, United States of America.
PLoS One. 2014 Mar 24;9(3):e92819. doi: 10.1371/journal.pone.0092819. eCollection 2014.
Septins are important components of the cytoskeleton that are highly conserved in eukaryotes and play major roles in cytokinesis, patterning, and many developmental processes. Septins form heteropolymers which assemble into higher-order structures including rings, filaments, and gauzes. In contrast to actin filaments and microtubules, the molecular mechanism by which septins assemble is not well-understood. Here, we report that in the filamentous fungus Aspergillus nidulans, four core septins form heteropolymeric complexes. AspE, a fifth septin lacking in unicellular yeasts, interacts with only one of the core septins, and only during multicellular growth. AspE is required for proper localization of three of the core septins, and requires this same subset of core septins for its own unique cortical localization. The ΔaspE mutant lacks developmentally-specific septin higher-order structures and shows reduced spore production and slow growth with low temperatures and osmotic stress. Our results show that at least two distinct septin heteropolymer populations co-exist in A. nidulans, and that while AspE is not a subunit of either heteropolymer, it is required for assembly of septin higher-order structures found in multicellular development.
Septin蛋白是细胞骨架的重要组成部分，在真核生物中高度保守，在胞质分裂、模式形成和许多发育过程中发挥主要作用。Septin蛋白形成异源聚合物，组装成包括环、丝和网状物在内的高阶结构。与肌动蛋白丝和微管不同，Septin蛋白组装的分子机制尚未得到很好的理解。在这里，我们报告在丝状真菌构巢曲霉中，四种核心Septin蛋白形成异源聚合物复合物。AspE是单细胞酵母中不存在的第五种Septin蛋白，仅与一种核心Septin蛋白相互作用，且仅在多细胞生长期间相互作用。AspE是三种核心Septin蛋白正确定位所必需的，并且其自身独特的皮质定位也需要这同一组核心Septin蛋白。ΔaspE突变体缺乏发育特异性的Septin高阶结构，并且在低温和渗透胁迫下孢子产量降低且生长缓慢。我们的结果表明，在构巢曲霉中至少存在两种不同的Septin异源聚合物群体，并且虽然AspE不是任何一种异源聚合物的亚基，但它是多细胞发育中发现的Septin高阶结构组装所必需的。
