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A physical perspective on cytoplasmic streaming.

Goldstein RE, van de Meent JW - Interface Focus (2015)

Bottom Line: Two spiralling bands of molecular motors at the cell periphery drive the cellular fluid up and down at speeds up to 100 µm s(-1), motion that has been hypothesized to mitigate the slowness of metabolite transport on these scales and to aid in homeostasis.This is the most organized instance of a broad class of continuous motions known as 'cytoplasmic streaming', found in a wide range of eukaryotic organisms-algae, plants, amoebae, nematodes and flies-often in unusually large cells.In this overview of the physics of this phenomenon, we examine the interplay between streaming, transport and cell size and discuss the possible role of self-organization phenomena in establishing the observed patterns of streaming.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences , University of Cambridge , Wilberforce Road, Cambridge CB3 0WA , UK.

ABSTRACT
Organisms show a remarkable range of sizes, yet the dimensions of a single cell rarely exceed 100 µm. While the physical and biological origins of this constraint remain poorly understood, exceptions to this rule give valuable insights. A well-known counterexample is the aquatic plant Chara, whose cells can exceed 10 cm in length and 1 mm in diameter. Two spiralling bands of molecular motors at the cell periphery drive the cellular fluid up and down at speeds up to 100 µm s(-1), motion that has been hypothesized to mitigate the slowness of metabolite transport on these scales and to aid in homeostasis. This is the most organized instance of a broad class of continuous motions known as 'cytoplasmic streaming', found in a wide range of eukaryotic organisms-algae, plants, amoebae, nematodes and flies-often in unusually large cells. In this overview of the physics of this phenomenon, we examine the interplay between streaming, transport and cell size and discuss the possible role of self-organization phenomena in establishing the observed patterns of streaming.

No MeSH data available.


Related in: MedlinePlus

Self-organization of cytoplasmic streaming in a mathematical model of Chara [174]. Colour coding corresponds to the z-component of an order parameter associated with actin filaments at the periphery, and white lines represent indifferent zones separating up- and down-streaming regions. Superimposed are streamlines of the cytoplasmic flow induced by the filament field, where the flow is directed from the thin end to the thick end of the individual lines. Panels show progression from random disorder through local order to complete steady cyclosis.
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RSFS20150030F5: Self-organization of cytoplasmic streaming in a mathematical model of Chara [174]. Colour coding corresponds to the z-component of an order parameter associated with actin filaments at the periphery, and white lines represent indifferent zones separating up- and down-streaming regions. Superimposed are streamlines of the cytoplasmic flow induced by the filament field, where the flow is directed from the thin end to the thick end of the individual lines. Panels show progression from random disorder through local order to complete steady cyclosis.

Mentions: This leads us finally to comment on the possibility that some forms of streaming appear through a process of self-organization. As long ago as 1953 [172], it was noted that cytoplasmic droplets extracted from characean algae could spontaneously self-organize into rotating fluid bodies. This presumably arises from myosin motors that walk along dislodged actin filaments and entrain fluid. Each of these motor/filament assemblies constitutes a force dipole in the fluid, and nearby assemblies will be attracted together if nearly parallel, leading to self-reinforcement of local order, leading eventually to long-range order. Further evidence for self-organization comes from much more recent work [173] in which steaming is completely disrupted through added chemicals (cytochalasin and oryzalin), which, when removed, allow streaming to be reconstituted. Strikingly, the indifferent zone appears in a new location. A mathematical model [174] that combines filament bundling, flow-induced reorientation and coupling to the curvature of the cell wall successfully reproduces much of this phenomenology, as shown in figure 5.Figure 5.


A physical perspective on cytoplasmic streaming.

Goldstein RE, van de Meent JW - Interface Focus (2015)

Self-organization of cytoplasmic streaming in a mathematical model of Chara [174]. Colour coding corresponds to the z-component of an order parameter associated with actin filaments at the periphery, and white lines represent indifferent zones separating up- and down-streaming regions. Superimposed are streamlines of the cytoplasmic flow induced by the filament field, where the flow is directed from the thin end to the thick end of the individual lines. Panels show progression from random disorder through local order to complete steady cyclosis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4590424&req=5

RSFS20150030F5: Self-organization of cytoplasmic streaming in a mathematical model of Chara [174]. Colour coding corresponds to the z-component of an order parameter associated with actin filaments at the periphery, and white lines represent indifferent zones separating up- and down-streaming regions. Superimposed are streamlines of the cytoplasmic flow induced by the filament field, where the flow is directed from the thin end to the thick end of the individual lines. Panels show progression from random disorder through local order to complete steady cyclosis.
Mentions: This leads us finally to comment on the possibility that some forms of streaming appear through a process of self-organization. As long ago as 1953 [172], it was noted that cytoplasmic droplets extracted from characean algae could spontaneously self-organize into rotating fluid bodies. This presumably arises from myosin motors that walk along dislodged actin filaments and entrain fluid. Each of these motor/filament assemblies constitutes a force dipole in the fluid, and nearby assemblies will be attracted together if nearly parallel, leading to self-reinforcement of local order, leading eventually to long-range order. Further evidence for self-organization comes from much more recent work [173] in which steaming is completely disrupted through added chemicals (cytochalasin and oryzalin), which, when removed, allow streaming to be reconstituted. Strikingly, the indifferent zone appears in a new location. A mathematical model [174] that combines filament bundling, flow-induced reorientation and coupling to the curvature of the cell wall successfully reproduces much of this phenomenology, as shown in figure 5.Figure 5.

Bottom Line: Two spiralling bands of molecular motors at the cell periphery drive the cellular fluid up and down at speeds up to 100 µm s(-1), motion that has been hypothesized to mitigate the slowness of metabolite transport on these scales and to aid in homeostasis.This is the most organized instance of a broad class of continuous motions known as 'cytoplasmic streaming', found in a wide range of eukaryotic organisms-algae, plants, amoebae, nematodes and flies-often in unusually large cells.In this overview of the physics of this phenomenon, we examine the interplay between streaming, transport and cell size and discuss the possible role of self-organization phenomena in establishing the observed patterns of streaming.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences , University of Cambridge , Wilberforce Road, Cambridge CB3 0WA , UK.

ABSTRACT
Organisms show a remarkable range of sizes, yet the dimensions of a single cell rarely exceed 100 µm. While the physical and biological origins of this constraint remain poorly understood, exceptions to this rule give valuable insights. A well-known counterexample is the aquatic plant Chara, whose cells can exceed 10 cm in length and 1 mm in diameter. Two spiralling bands of molecular motors at the cell periphery drive the cellular fluid up and down at speeds up to 100 µm s(-1), motion that has been hypothesized to mitigate the slowness of metabolite transport on these scales and to aid in homeostasis. This is the most organized instance of a broad class of continuous motions known as 'cytoplasmic streaming', found in a wide range of eukaryotic organisms-algae, plants, amoebae, nematodes and flies-often in unusually large cells. In this overview of the physics of this phenomenon, we examine the interplay between streaming, transport and cell size and discuss the possible role of self-organization phenomena in establishing the observed patterns of streaming.

No MeSH data available.


Related in: MedlinePlus