Actin networks in certain URLanisms exhibit a complex pattern-forming dynamics that starts with the appearance of static `spots ' of actin on the cell cortex. Spots soon become mobile,  and eventually give rise to , and coexist with, traveling waves of actin. Waves confer motility upon the cell by impinging on its periphery. Here we describe a possible physical mechanism for this distinctive set of dynamic transformations . Starting from the observation that excitable reaction-diffusion models of chemical systems can describe both localized spots and traveling waves, we augment one such model with a variable describing the spatial orientation of its chief constituent . We consider this constituent to be a caricature of polymerized actin, and regard its orientation as a measure of local actin fiber alignment. This spatial anisotropy, which is not possessed by conventional chemical species, profoundly affects localized structures to drive a transformation at fixed parameter values from static spots to moving spots to waves.
Actin networks in certain URLanisms exhibit a complex pattern-forming dynamics that starts with the appearance of static spots of actin on the cell cortex. Spots soon become mobile, executing persistent random walks, and eventually give rise to traveling waves of actin. Here we describe a possible physical mechanism for this distinctive set of dynamic transformations , by equipping an excitable reaction-diffusion model with a field describing the spatial orientation of its chief constituent (which we consider to be actin). The interplay of anisotropic actin growth and spatial inhibition drives a transformation at fixed parameter values from static spots to moving spots to waves.
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`spots '
spots
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executing persistent random walks,
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, and coexist with,
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Waves confer motility upon the cell by impinging on its periphery.
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. Starting from the observation that
, by equipping an
D
models of chemical systems can describe both localized spots and traveling waves, we augment one such
R
variable
field
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. We consider this constituent to be a caricature of polymerized actin, and regard its orientation as a measure of local actin fiber alignment. This spatial anisotropy, which is not possessed by conventional chemical species, profoundly affects localized structures to drive
(which we consider to be actin). The interplay of anisotropic actin growth and spatial inhibition drives