通过模板切割进行微管扩增的临界阈值
Critical threshold for microtubule amplification through templated severing
摘要：
植物幼苗下胚轴细胞的皮层微管阵列在光照下发生了显著的、发育上显著的重定向。这个过程是由纵向微管群体的指数扩增驱动的，纵向微管群体是通过切断位于与预先存在的横向阵列的微管交叉处的事件而产生的。我们提出了一个动态的一维模型微管扩增通过这种类型的模板切断。我们专注于新创建的滞后微管切断后立即救援的概率的作用，观察到的重定向过程的一个特征。利用随机模拟，我们表明，在无界微管生长的动态机制中，发生扩增不需要该概率的有限值，但确实强烈影响扩增的程度，从而影响重定向过程的速度。相比之下，在有界微管生长的制度，我们表明，放大只发生在一个临界阈值以上。我们构建了一个近似的分析理论，基于先验限制的交叉事件的数量考虑，这使我们能够预测观察到的救援后切断概率的临界值具有合理的精度。
英文摘要：
The cortical microtubule array of dark-grown hypocotyl cells of plant seedlings undergoes a striking, and developmentally significant, reorientation upon exposure to light. This process is driven by the exponential amplification of a population of longitudinal microtubules, created by severing events localized at crossovers with the microtubules of the pre-existing transverse array. We present a dynamic one-dimensional model for microtubule amplification through this type of templated severing. We focus on the role of the probability of immediate rescue-after-severing of the newly-created lagging microtubule, observed to be a characteristic feature of the reorientation process. Employing stochastic simulations, we show that in the dynamic regime of unbounded microtubule growth, a finite value of this probability is not required for amplification to occur, but does strongly influence the degree of amplification, and hence the speed of the reorientation process. In contrast, in the regime of bounded microtubule growth, we show that amplification only occurs above a critical threshold. We construct an approximate analytical theory, based on a priori limiting the number of crossover events considered, which allows us to predict the observed critical value of the rescue-after-severing probability with reasonable accuracy.
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