P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mec...P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mechanism of the localization phenomena is induced by liquid-liquid phase transition(LLPT),in which the polarity proteins control the saturation point of P granules.In the present study,we propose that the P granules phase transition can be triggered by the cytoplasmic streaming.A two-phase flow model is employed to simulate the localization of P granules,i.e.,the cytoplasm is considered as a liquid phase,and the droplet-like P granules are another liquid phase.With the presence of the cytoplasmic streaming,P granules,initially distributing uniformly in the entire one-cell embryo,eventually condense/dissolve in the cytoplasm phase,regulated by difference between the saturation pressure and the hydrodynamic pressure.The numerical results reveal that the cytoplasmic streaming has significant effects on the localization of P granules,as well as the embryo division.展开更多
Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse a...Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse array of mechanisms for streaming motions. This paper focuses on the re-emergence of contraction among the molecular mecha-nisms proposed for protoplasmic streaming during the twentieth century. The revival of contraction is a result of a broader transition from colloidal chemistry to a macro- molecular approach to the chemistry of proteins, the recognition of the phenomena of shuttle streaming and the pulse of protoplasm, and the influential analogy between protoplasmic streaming and muscle contraction.展开更多
The pollen tube is fundamental for the reproduction of seed plants. Characteristically, it grows relatively quickly and uni-directionally ("polarized growth") to extend the male gametophyte to reach the female gam...The pollen tube is fundamental for the reproduction of seed plants. Characteristically, it grows relatively quickly and uni-directionally ("polarized growth") to extend the male gametophyte to reach the female gametophyte. The pollen tube forms a channel through which the sperm cells move so that they can reach their targets in the ovule. To grow quickly and directionally, the pollen tube requires an intense movement of organelles and vesicles that allows the cell's contents to be distributed to sustain the growth rate. While the various organelles distribute more or less uniformly within the pollen tube, Golgi-released secretory vesicles accumulate massively at the pollen tube apex, that is, the growing region. This intense movement of organelles and vesicles is dependent on the dynamics of the cytoskeleton, which reorganizes differentially in response to external signals and coordinates membrane trafficking with the growth rate of pollen tubes.展开更多
A striking characteristic of plant cells is that their organelles can move rapidly through the cell. This movement, commonly referred to as cytoplasmic streaming, has been observed for over 200 years, but we are only ...A striking characteristic of plant cells is that their organelles can move rapidly through the cell. This movement, commonly referred to as cytoplasmic streaming, has been observed for over 200 years, but we are only now beginning to decipher the mechanisms responsible for it. The identification of the myosin motor proteins responsible for these movements allows us to probe the regulatory events that coordinate organelle displacement with normal cell physiology. This review will highlight several recent developments that have provided new insight into the regulation of organelle movement, both at the cellular level and at the molecular level.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11272197,and 11372175)the Innovation Program of Shanghai Municipality Education Commission,China(Grant No.14ZZ095)
文摘P granules are germ granules contained in Caenorhabditis elegans germ cells.The first germ cell is specified by the one-cell embryo in which P granules localize to the posterior.Previous studies suggested that the mechanism of the localization phenomena is induced by liquid-liquid phase transition(LLPT),in which the polarity proteins control the saturation point of P granules.In the present study,we propose that the P granules phase transition can be triggered by the cytoplasmic streaming.A two-phase flow model is employed to simulate the localization of P granules,i.e.,the cytoplasm is considered as a liquid phase,and the droplet-like P granules are another liquid phase.With the presence of the cytoplasmic streaming,P granules,initially distributing uniformly in the entire one-cell embryo,eventually condense/dissolve in the cytoplasm phase,regulated by difference between the saturation pressure and the hydrodynamic pressure.The numerical results reveal that the cytoplasmic streaming has significant effects on the localization of P granules,as well as the embryo division.
文摘Explanations for protoplasmic streaming began with appeals to contraction in the eighteenth century and ended with appeals to contraction in the twentieth. During the intervening years, biologists proposed a diverse array of mechanisms for streaming motions. This paper focuses on the re-emergence of contraction among the molecular mecha-nisms proposed for protoplasmic streaming during the twentieth century. The revival of contraction is a result of a broader transition from colloidal chemistry to a macro- molecular approach to the chemistry of proteins, the recognition of the phenomena of shuttle streaming and the pulse of protoplasm, and the influential analogy between protoplasmic streaming and muscle contraction.
文摘The pollen tube is fundamental for the reproduction of seed plants. Characteristically, it grows relatively quickly and uni-directionally ("polarized growth") to extend the male gametophyte to reach the female gametophyte. The pollen tube forms a channel through which the sperm cells move so that they can reach their targets in the ovule. To grow quickly and directionally, the pollen tube requires an intense movement of organelles and vesicles that allows the cell's contents to be distributed to sustain the growth rate. While the various organelles distribute more or less uniformly within the pollen tube, Golgi-released secretory vesicles accumulate massively at the pollen tube apex, that is, the growing region. This intense movement of organelles and vesicles is dependent on the dynamics of the cytoskeleton, which reorganizes differentially in response to external signals and coordinates membrane trafficking with the growth rate of pollen tubes.
基金supported by a grant from theNational Science Foundation (MCB-0822111) to A.N
文摘A striking characteristic of plant cells is that their organelles can move rapidly through the cell. This movement, commonly referred to as cytoplasmic streaming, has been observed for over 200 years, but we are only now beginning to decipher the mechanisms responsible for it. The identification of the myosin motor proteins responsible for these movements allows us to probe the regulatory events that coordinate organelle displacement with normal cell physiology. This review will highlight several recent developments that have provided new insight into the regulation of organelle movement, both at the cellular level and at the molecular level.