Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
Phys Rev E. 2023 Jul;108(1-1):014401. doi: 10.1103/PhysRevE.108.014401.
Saccharomyces cerevisiae and Candida albicans, the two well-known human pathogens, can be found in all three morphologies, i.e., yeast, pseudohyphae, and true hyphae. The cylindrical daughter-bud (germ tube) grows very long for true hyphae, and the cell cycle is delayed compared to the other two morphologies. The place of the nuclear division is specific for true hyphae determined by the position of the septin ring. However, the septin ring can localize anywhere inside the germ tube, unlike the mother-bud junction in budding yeast. Since the nucleus often migrates a long path in the hyphae, the underlying mechanism must be robust for executing mitosis in a timely manner. We explore the mechanism of nuclear migration through hyphae in light of mechanical interactions between astral microtubules and the cell cortex. We report that proper migration through constricted hyphae requires a large dynein pull applied on the astral microtubules from the hyphal cortex. This is achieved when the microtubules frequently slide along the hyphal cortex so that a large population of dyneins actively participate, pulling on them. Simulation shows timely migration when the dyneins from the mother cortex do not participate in pulling on the microtubules. These findings are robust for long migration and positioning of the nucleus in the germ tube at the septin ring.
酿酒酵母和白色念珠菌是两种众所周知的人类病原体，它们可以呈现出三种形态，即酵母、假菌丝和真菌丝。真菌丝的圆柱状子芽（芽管）生长得非常长，与另外两种形态相比，细胞周期会延迟。核分裂的位置对于真菌丝是特定的，由隔膜环的位置决定。然而，与出芽酵母中的母芽连接点不同，隔膜环可以定位在芽管的任何内部位置。由于细胞核经常在菌丝中迁移很长的路径，因此必须有一个强大的机制来及时执行有丝分裂。我们根据星体微管和细胞皮层之间的机械相互作用，探讨了核通过菌丝迁移的机制。我们报告说，在受限制的菌丝中进行适当的迁移需要从菌丝皮层对星体微管施加大量的动力蛋白拉力。当微管经常沿着菌丝皮层滑动，使大量的动力蛋白积极参与并拉动它们时，就可以实现这一点。模拟表明，当来自母皮层的动力蛋白不参与拉动微管时，核可以及时迁移。这些发现对于核在隔膜环处的芽管中的长距离迁移和定位是稳健的。
