Mass flow and pressure-driven hyphal extension in Neurospora crassa
Mass flow and pressure-driven hyphal extension in Neurospora crassa
复制标题
DOI：
10.1099/mic.0.27947-0
复制
发表时间：
2005-08-01
期刊：
影响因子：
2.8
通讯作者：
Lew, RR
中科院分区：
文献类型：
--
作者：
Lew, RR
粗脉孢菌主干菌丝细胞质的质量流是通过向菌丝内注入油滴直接证实的。液滴的运动方式类似于菌丝内的细胞质颗粒和液泡。质量流的方向是朝向殖民地边缘的生长菌丝尖端。根据流速（约5 μ m·s ~（-1））、菌丝半径和细胞质粘度的估计，雷诺数约为10 ~（-4），表明质量流是层流。因此，可以使用Poiseulle方程来计算质量流所需的压力梯度：0005-0（.）1 bar cm（-1）（取决于中隔孔半径和细胞质粘度所用的值）。这些值与菌丝的正常静水压力（4-5巴）相比非常小。质量流在氰化物抑制呼吸或产生细胞外渗透梯度后停止。这种流动可能是由菌丝沿着不同的离子运输产生的内部渗透梯度引起的。顶端的细胞质迁移的速度与顶端延伸的速度相同，注入顶端附近的油滴也一样。因此，除了由分子马达介导的细胞器定位之外，压力驱动的质量流可能是菌丝延伸的组成部分。
Mass flow of cytoplasm in Neurospora crassa trunk hyphae was directly confirmed by injecting oil droplets into the hyphae. The droplets move in a manner similar to cytoplasmic particles and vacuoles within the hyphae. The direction of mass flow is towards the growing hyphal tips at the colony edge. Based on flow velocities (about 5 mu m s(-1)), hyphal radius and estimates of cytoplasm viscosity, the Reynolds number is about 10(-4), indicating that mass flow is laminar. Therefore, the Poiseulle equation can be used to calculate the pressure gradient required for mass flow: 0(.)0005-0(.)1 bar cm(-1) (depending on the values used for septal pore radius and cytoplasmic viscosity). These values are very small compared to the normal hydrostatic pressure of the hyphae (4-5 bar). Mass flow stops after respiratory inhibition with cyanide, or creation of an extracellular osmotic gradient. The flow is probably caused by internal osmotic gradients created by differential ion transport along the hyphae. Apical cytoplasm migrates at the same rate as tip extension, as do oil droplets injected near the tip. Thus, in addition to organelle positioning mediated by molecular motors, pressure-driven mass flow may be an integral part of hyphal extension.