Mechanism of signal propagation in Physarum polycephalum
Mechanism of signal propagation in Physarum polycephalum
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DOI：
10.1073/pnas.1618114114
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发表时间：
2017-05-16
影响因子：
11.1
通讯作者：
Brenner, Michael P.
中科院分区：
文献类型：
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作者：
Alim, Karen;Andrew, Natalie;Brenner, Michael P.
复杂的行为通常与动物有关，但整合信息和作为协调个体发挥作用的能力也是黏菌和真菌等生物体普遍存在但知之甚少的特征。疟原虫黏菌以网络的形式生长，并使用灵活的、未分化的身体计划来觅食。个体如何通过其网络进行通信仍然是一个谜，但多头绒泡菌已经成为一种用于探索涌现动力学的新模型。在P. polycephalum内，细胞质在由管的横截面收缩驱动的蠕动波中穿梭。我们首先跟踪P. polycephalum对局部营养刺激的反应，并观察到收缩增加的前沿。前传播的速度相当于流动驱动的颗粒分散。我们基于这些数据建立了一个数学模型，并在综合实验和模型中确定了信号在体内传播的机制：营养刺激触发了信号分子的释放。该分子被流体流平流输送，但同时通过在其行进时引起收缩幅度的局部增加来劫持流生成。这个分子启动了一个反馈回路，使它能够自己运动。这一机制解释了以前令人困惑的现象，包括蠕动波对生物体大小的适应，以及多头绒螯蟹在食物来源之间找到最短路线的能力。一个简单的反馈似乎引起了多头绒螯蟹的复杂行为，同样的机制可能在成千上万具有类似行为的其他物种中发挥作用。
Complex behaviors are typically associated with animals, but the capacity to integrate information and function as a coordinated individual is also a ubiquitous but poorly understood feature of organisms such as slime molds and fungi. Plasmodial slime molds grow as networks and use flexible, undifferentiated body plans to forage for food. How an individual communicates across its network remains a puzzle, but Physarum polycephalum has emerged as a novel model used to explore emergent dynamics. Within P. polycephalum, cytoplasm is shuttled in a peristaltic wave driven by cross-sectional contractions of tubes. We first track P. polycephalum's response to a localized nutrient stimulus and observe a front of increased contraction. The front propagates with a velocity comparable to the flow-driven dispersion of particles. We build a mathematical model based on these data and in the aggregate experiments and model identify the mechanism of signal propagation across a body: The nutrient stimulus triggers the release of a signaling molecule. The molecule is advected by fluid flows but simultaneously hijacks flow generation by causing local increases in contraction amplitude as it travels. The molecule is initiating a feedback loop to enable its own movement. This mechanism explains previously puzzling phenomena, including the adaptation of the peristaltic wave to organism size and P. polycephalum's ability to find the shortest route between food sources. A simple feedback seems to give rise to P. polycephalum's complex behaviors, and the same mechanism is likely to function in the thousands of additional species with similar behaviors.