Gravitaxis in Flagellates

Dp, Häder

doi:10.2307/1542586

Cited by 10 publications

(1 citation statement)

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“…25 Numerous experiments in real microgravity (on sounding rockets, satellites and the Space Shuttle) documented that the cells are definitively able to respond to gravity rather than with respect to the magnetic field of the Earth. 26 The threshold for the gravity-induced response is found at ≤0.16 g. 27 In contrast to an earlier hypothesis, which posited that the cells are passively aligned by a pure buoy mechanism resulting from tail-heavy cells, gravitaxis has been shown to rely on a physiological active gravireceptor. In contrast to organisms, which possess statoliths, in Euglena the whole cell body being heavier (up to 1.05 g/ml) than the surrounding medium, 28 presses on the lower cell membrane.…”

Section: Introductionmentioning

confidence: 88%

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

et al. 2017

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We have selected five evolutionary very different biological systems ranging from unicellular protists via algae and higher plants to human cells showing responses to the gravity vector of the Earth in order to compare their graviperception mechanisms. All these systems use a mass, which may either by a heavy statolith or the whole content of the cell heavier than the surrounding medium to operate on a gravireceptor either by exerting pressure or by pulling on a cytoskeletal element. In many cases the receptor seems to be a mechanosensitive ion channel activated by the gravitational force which allows a gated ion flux across the membrane when activated. This has been identified in many systems to be a calcium current, which in turn activates subsequent elements of the sensory transduction chain, such as calmodulin, which in turn results in the activation of ubiquitous enzymes, gene expression activation or silencing. Naturally, the subsequent responses to the gravity stimulus differ widely between the systems ranging from orientational movement and directed growth to physiological reactions and adaptation to the environmental conditions.

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Section: Introductionmentioning

confidence: 88%

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

et al. 2017

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Gravity‐sensing and gravity‐related signaling pathways in unicellular model systems of protists and plants

Hemmersbach¹,

Braun

2006

Signal Transduction

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Gravity sensing, gravity‐dependent signaling pathways and resulting graviresponses are found even in single cells as shown in studies on unicellular animal and plant model systems. Although the gravity‐dependent responses of single‐celled systems are obviously very different, the presented experimental data from experiments on ground and in space reveal that especially the early phases of gravity sensing share common features. The gravisensory processes can be reduced to two principles: perception via intracellular statoliths and via the whole protoplast. Gravisensory ion channels and cascades of ubiquitous second messengers are proposed in most gravity‐dependent signaling pathways and have been identified in some cases. Cytoskeletal elements have been shown to play a master role in the complex processes of gravity sensing and graviorientation. Research on ground has been complemented with experiments in microgravity, which greatly contributed to our understanding of gravi‐related signaling processes.

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Graviresponses in fungi and slime molds

Hock¹,

Häder²

2006

Signal Transduction

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The analysis of gravisensing in fungi has not yet proceeded as far as in other systems, such as sensory cells for maintenance of equilibrium in crustaceans and vertebrates, Chara rhizoids or plant roots with regard to positive gravitropism. However, considerable progress has recently been made with several fungal systems in the field of graviresponses. This particularly holds true for the molecular basis of primary events. In this review three systems of increasing complexity are considered: the slime molds Physarum and Dictyostelium, which exhibit gravitaxis, the negative gravitropic sporangium of the zygomycete Phycomyces as a single cell structure with the fastest graviresponses known so far, and the fruit bodies of the basidiomycetes Coprinus and Flammulina as highly complex structures with the ability to generate positional information and cell signalling in the context of negative gravitropism.

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Gravitaxis in Flagellates

Cited by 10 publications

References 0 publications

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

Gravireceptors in eukaryotes—a comparison of case studies on the cellular level

Gravity‐sensing and gravity‐related signaling pathways in unicellular model systems of protists and plants

Graviresponses in fungi and slime molds

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