Diffusive Promotion by Velocity Gradient of Cytoplasmic Streaming (CPS) in Nitella Internodal Cells

• Published in: PloS one Vol. 10; no. 12; p. e0144938
• Main Authors: Kikuchi, Kenji, Mochizuki, Osamu
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 22-12-2015; Public Library of Science (PLoS)
• Subjects: Advection; Bioengineering; Cell migration; Cell motility; Cellular structure; Convection; Cytoplasm; Cytoplasmic filaments; Cytoplasmic Streaming; Cytosol; Diffusion; Endoplasmic reticulum; Flow; Flow visualization; Fluid; Fluid mechanics; Fluids; Fluorescence; Genetic aspects; Hydrodynamics; Metabolism; Microscopy; Molecular Motor Proteins - metabolism; Motility; Nanoparticles; Nitella; Nitella - physiology; Nitella - ultrastructure; Nutrients; Organelles; Physiological aspects; Physiology; Plant Proteins - metabolism; Proteins; Studies; Velocity; Velocity distribution; Velocity gradient; Japan
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0144938

Cytoplasmic streaming (CPS) is well known to assist the movement of nutrients, organelles and genetic material by transporting all of the cytoplasmic contents of a cell. CPS is generated by motility organelles that are driven by motor proteins near a membrane surface, where the CPS has been found to have a flat velocity profile in the flow field according to the sliding theory. There is a consistent mixing of contents inside the cell by CPS if the velocity gradient profile is flattened, which is not assisted by advection diffusion but is only supported by Brownian diffusion. Although the precise flow structure of the cytoplasm has an important role for cellular metabolism, the hydrodynamic mechanism of its convection has not been clarified. We conducted an experiment to visualise the flow of cytoplasm in Nitella cells by injecting tracer fluorescent nanoparticles and using a flow visualisation system in order to understand how the flow profile affects their metabolic system. We determined that the velocity field in the cytosol has an obvious velocity gradient, not a flattened gradient, which suggests that the gradient assists cytosolic mixing by Taylor-Aris dispersion more than by Brownian diffusion.