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Gravitaxis in Euglena

Häder, Donat-Peter and Hemmersbach, Ruth (2017) Gravitaxis in Euglena. In: Euglena: Biochemistry, Cell and Molecular Biology Advances in Experimental Medicine and Biology (Adv Exp Med Biol), 979. Springer International Publishing. pp. 237-266. ISBN 978-3-319-54908-8 (Print) 978-3-319-54910-1 (Online). ISSN 0065-2598

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Official URL: https://link.springer.com/chapter/10.1007%2F978-3-319-54910-1_12

Abstract

Motile microorganisms utilize a number of responses to external stimuli including light, temperature, chemicals as well as magnetic and electric fields. Gravity is a major clue to select a niche in their environment. Positive gravitaxis leads an organism down into the water column and negative gravitaxis brings it to the surface. In Euglena the precision of gravitaxis is regulated by an internal rhythm entrained by the daily light/dark cycle. This and the cooperation with phototaxis bring the cells into an optimal position in the water column. In the past a passive orientation based on a buoy mechanism has been proposed for Euglena gracilis, but now it has been proven that this flagellate possesses a physiological gravireceptor and an active orientation. Numerous experiments in space using satellites, rockets and shuttles as well as in parabolic flights have been conducted as well as in functional weightlessness (simulated microgravity) on ground-based facilities such as clinostats to characterize the gravitaxis of Euglena. The threshold for gravity perception was determined and physiological, biochemical and molecular components of the signal transduction chain have been identified. In contrast to higher plants, some algae and ciliates, Euglena does not possess sedimenting statoliths to detect the direction of the gravity vector of the Earth. The gravireceptors were found to be mechano-sensitive Ca2+-conducting ion channels thought to be located at the front end of the cell underneath the trailing flagellum. When activated by gravity-induced pressure due to sedimentation of the whole cell body, they allow a passive influx of calcium along a previously established ion gradient. The entering calcium binds to a specific calmodulin (CaM.2) which in turn activates an adenylyl cyclase producing cAMP from ATP. This cAMP is believed to activate a specific protein kinase A (PK.4), which is postulated to phosphorylate proteins inside the flagellum resulting in a bending and thus a course correction and reorientation with respect to the direction of the gravity vector. The elements of the signal transduction chain have been characterized by inhibitors and by RNAi to prove their involvement in gravitaxis.

Item URL in elib:https://elib.dlr.de/112914/
Document Type:Book Section
Title:Gravitaxis in Euglena
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Häder, Donat-Peteremeritus from friedrich-alexander-universität erlangen, institut für biologiehttps://orcid.org/0000-0002-4295-5660
Hemmersbach, Ruthgerman aerospace centre (dlr), institute of aerospace medicine, gravitational biology, cologne, germanyhttps://orcid.org/0000-0001-5308-6715
Date:21 April 2017
Journal or Publication Title:Euglena: Biochemistry, Cell and Molecular Biology
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Volume:979
DOI :10.1007/978-3-319-54910-1_12
Page Range:pp. 237-266
Editors:
EditorsEmail
Schwartzbach, Steven D.UNSPECIFIED
Shigeoka, ShigeruUNSPECIFIED
Publisher:Springer International Publishing
Series Name:Advances in Experimental Medicine and Biology (Adv Exp Med Biol)
ISSN:0065-2598
ISBN:978-3-319-54908-8 (Print) 978-3-319-54910-1 (Online)
Status:Published
Keywords:Adenylyl cyclase, Calmodulin, Euglena, Gravireceptor, Gravitaxis, Hypergravity, Microgravity, Protein kinase, Sensory transduction, Space flight, cAMP
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Biowissenschaftliche Exp.-vorbereitung, R - Vorhaben Biowissenschaftliche Nutzerunterstützung
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Gravitational Biology
Deposited By: Duwe, Helmut
Deposited On:05 Jul 2017 11:20
Last Modified:05 Jul 2017 11:20

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