Tip-growing fungal cells maintain the cell polarity at the apical regions and elongate by de novo synthesis of cell wall. Cell polarity and growth rate affect the mycelial morphogenesis, however, it remains unclear how they act cooperatively to determine cell shape. Here we investigated their relationship by analyzing hyphal tip growth of filamentous fungi growing inside extremely narrow 1µm-width channels of microfluidic devices. Since the channels are much narrower than the diameter of hyphae, the hyphae must change its morphology when they grow through the channels. Live imaging analysis revealed that hyphae of some species continued growing through the channels, whereas hyphae of other species often ceased growing when passing through the channels or lost the cell polarity after emerging from the channels. Fluorescence live imaging analysis of the Spitzenkörper, a collection of secretory vesicles and polarity-related proteins at hyphal tips, in Neurospora crassa hyphae indicates that hyphal tip growth requires a very delicate balance of ordered exocytosis to maintain polarity in spatially confined environments. We analyzed the mycelial growth of seven fungal species from different lineages, which also include phytopathogenic fungi. This comparative cell biology showed that the growth defects in the channels were not correlated with their taxonomic classification nor with the width of hyphae, but, correlated with the hyphal elongation rate. This is the first report indicating a trade-off between plasticity and velocity in mycelial growth, and serves to understand fungal invasive growth into substrates or plant/animal cells, with direct impact on fungal biotechnology, ecology and pathogenicity.

中文翻译：

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菌丝生长中可塑性与速度之间的权衡

顶端生长的真菌细胞在顶端区域保持细胞极性，并通过从头合成细胞壁而伸长。细胞的极性和生长速度影响菌丝体的形态发生，但是，尚不清楚它们如何协同作用来确定细胞的形状。在这里，我们通过分析在微流体装置极窄的1µm宽度通道内生长的丝状真菌的菌丝尖端生长来研究它们的关系。由于通道比菌丝的直径窄得多，因此当菌丝通过通道生长时，必须改变其形态。实时成像分析显示，某些物种的菌丝在通道中持续生长，而其他物种的菌丝在通过通道时常常停止生长，或者在从通道中出来后失去细胞极性。粗糙孢菌丝菌丝表明菌丝尖端生长需要有序的胞吐作用非常微妙的平衡，以在空间受限的环境中保持极性。我们分析了来自不同谱系的七个真菌物种的菌丝生长，其中也包括植物致病真菌。这种比较的细胞生物学结果表明，通道中的生长缺陷与它们的分类学分类和菌丝的宽度均不相关，而与菌丝的延伸率相关。这是第一个表明菌丝体生长的可塑性与速度之间权衡的报告，并有助于了解真菌侵入基质或植物/动物细胞的侵袭性生长，直接影响真菌的生物技术，生态学和致病性。