The involvement of a protein kinase in phototaxis and gravitaxis of Euglena gracilis

Journal article

Publication Details

Author(s): Daiker V, Häder DP, Richter P, Lebert M
Journal: Planta
Publisher: Springer Verlag (Germany)
Publication year: 2011
Volume: 233
Journal issue: 5
Pages range: 1055-1062
ISSN: 0032-0935


The unicellular flagellate Euglena gracilis shows positive phototaxis at low-light intensities (< 10 W/m(2)) and a negative one at higher irradiances (> 10 W/m(2)). Phototaxis is based on blue light-activated adenylyl cyclases, which produce cAMP upon irradiation. In the absence of light the cells swim upward in the water column (negative gravitaxis). The results of sounding rocket campaigns and of a large number of ground experiments led to the following model of signal perception and transduction in gravitaxis of E. gracilis: The body of the cell is heavier than the surrounding medium, sediments and thereby exerts a force onto the lower membrane. Upon deviation from a vertical swimming path mechano-sensitive ion channels are activated. Calcium is gated inwards which leads to an increase in the intracellular calcium concentration and causes a change of the membrane potential. After influx, calcium activates one of several calmodulins found in Euglena, which in turn activates an adenylyl cyclase (different from the one involved in phototaxis) to produce cAMP from ATP. One further element in the sensory transduction chain of both phototaxis and gravitaxis is a specific protein kinase A. We found five different protein kinases A in E. gracilis. The blockage of only one of these (PK.4, accession No. EU935859) by means of RNAi inhibited both phototaxis and gravitaxis, while inhibition of the other four affected neither phototaxis nor gravitaxis. It is assumed that cAMP directly activates this protein kinase A which may in turn phosphorylate a protein involved in the flagellar beating mechanism.

FAU Authors / FAU Editors

Daiker, Viktor Dr.
Lehrstuhl für Zellbiologie
Häder, Donat-Peter Prof. Dr.
Naturwissenschaftliche Fakultät
Lebert, Michael PD Dr.
Lehrstuhl für Zellbiologie
Richter, Peter Dr.
Lehrstuhl für Zellbiologie

How to cite

Daiker, V., Häder, D.-P., Richter, P., & Lebert, M. (2011). The involvement of a protein kinase in phototaxis and gravitaxis of Euglena gracilis. Planta, 233(5), 1055-1062.

Daiker, Viktor, et al. "The involvement of a protein kinase in phototaxis and gravitaxis of Euglena gracilis." Planta 233.5 (2011): 1055-1062.


Last updated on 2018-20-07 at 19:23

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