Aspergillus nidulans class V and VI chitin synthases CsmA and CsmB, each with a myosin motor-like domain, perform compensatory functions that are essential for hyphal tip growth
Aspergillus nidulans class V and VI chitin synthases CsmA and CsmB, each with a myosin motor-like domain, perform compensatory functions that are essential for hyphal tip growth
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DOI：
10.1111/j.1365-2958.2006.05030.x
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发表时间：
2006-03-01
影响因子：
3.6
通讯作者：
Horiuchi, H
中科院分区：
文献类型：
--
作者：
Takeshita, N;Yamashita, S;Horiuchi, H
细胞壁成分如几丁质的极化合成对于丝状真菌菌丝尖端的生长至关重要。已知肌动蛋白细胞骨架在构巢曲霉菌丝极性的确定中发挥重要作用。此前，我们认为 CsmA 是一种具有肌球蛋白运动样结构域 (MMD) 的几丁质合酶，以依赖于 MMD 和肌动蛋白细胞骨架之间相互作用的方式参与极化几丁质合成。基因组数据库表明构巢曲霉拥有另一个编码另一种具有 MMD 的几丁质合酶的基因。在这项研究中，我们对这个基因进行了表征，并将其命名为 csmB。所检查的 csmB 无效突变体是可行的，尽管它们表现出有缺陷的表型，包括气球和菌丝内菌丝的形成以及顶端下区域的裂解，这与 csmA 无效突变体获得的结果相似。此外，csmA csmB 双无效突变体不能存活。 csmB 被删除且 csmA 的表达受 alcA 启动子控制的突变体是可行的，但在 alcA 抑制条件下菌丝生长严重受损。我们发现，带有三个 FLAG 表位标签拷贝的 CsmB 位于菌丝尖端并形成隔膜，并且 CsmB 的 MMD 能够在体外与肌动蛋白丝结合。这些结果表明 CsmA 和 CsmB 执行对菌丝尖端生长至关重要的补偿功能。
The polarized synthesis of cell wall components such as chitin is essential for the hyphal tip growth of filamentous fungi. The actin cytoskeleton is known to play important roles in the determination of hyphal polarity in Aspergillus nidulans. Previously, we suggested that CsmA, a chitin synthase with a myosin motor-like domain (MMD), was involved in polarized chitin synthesis in a manner dependent on the interaction between the MMD and the actin cytoskeleton. The genome database indicates that A. nidulans possesses another gene encoding another chitin synthase with an MMD. In this study, we characterized this gene, which we designated csmB. The csmB null mutants examined were viable, although they exhibited defective phenotypes, including the formation of balloons and intrahyphal hyphae and the lysis of subapical regions, which were similar to those obtained with csmA null mutants. Moreover, csmA csmB double null mutants were not viable. Mutants in which csmB was deleted and the expression of csmA was under the control of the alcA promoter were viable but severely impaired in terms of hyphal growth under alcA-repressing conditions. We revealed that CsmB with three copies of a FLAG epitope tag localized at the hyphal tips and forming septa, and that the MMD of CsmB was able to bind to actin filaments in vitro. These results suggest that CsmA and CsmB perform compensatory functions that are essential for hyphal tip growth.