Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America.
PLoS One. 2012;7(2):e31218. doi: 10.1371/journal.pone.0031218. Epub 2012 Feb 16.
Because of the industrial and medical importance of members of the fungal genus Aspergillus, there is considerable interest in the functions of cytoskeletal components in growth and secretion in these organisms. We have analyzed the genome of Aspergillus nidulans and found that there are two previously unstudied myosin genes, a myosin II homolog, myoB (product = MyoB) and a myosin V homolog, myoE (product = MyoE). Deletions of either cause significant growth defects. MyoB localizes in strings that coalesce into contractile rings at forming septa. It is critical for septation and normal deposition of chitin but not for hyphal extension. MyoE localizes to the Spitzenkörper and to moving puncta in the cytoplasm. Time-lapse imaging of SynA, a v-SNARE, reveals that in myoE deletion strains vesicles no longer localize to the Spitzenkörper. Tip morphology is slightly abnormal and branching occurs more frequently than in controls. Tip extension is slower than in controls, but because hyphal diameter is greater, growth (increase in volume/time) is only slightly reduced. Concentration of vesicles into the Spitzenkörper before incorporation into the plasma membrane is, thus, not required for hyphal growth but facilitates faster tip extension and a more normal hyphal shape.
由于真菌属 Aspergillus 成员在工业和医学上的重要性，人们对这些生物中细胞骨架成分在生长和分泌中的功能产生了浓厚的兴趣。我们分析了 Aspergillus nidulans 的基因组，发现有两个以前未研究过的肌球蛋白基因，一个肌球蛋白 II 同源物，myoB（产物=MyoB）和一个肌球蛋白 V 同源物，myoE（产物=MyoE）。缺失任一个都会导致明显的生长缺陷。MyoB 定位于字符串中，在形成隔膜时聚合成收缩环。它对隔膜的形成和几丁质的正常沉积至关重要，但对菌丝的延伸不重要。MyoE 定位于 Spitzenkörper 和细胞质中的移动斑点。SynA（v-SNARE）的延时成像显示，在 myoE 缺失菌株中，囊泡不再定位于 Spitzenkörper。尖端形态略有异常，分枝比对照更频繁。尖端延伸比对照慢，但由于菌丝直径更大，生长（体积/时间的增加）只是略有减少。因此，囊泡在整合到质膜之前浓缩到 Spitzenkörper 中并不是菌丝生长所必需的，但有利于更快的尖端延伸和更正常的菌丝形状。
