Sensory transduction of gravitaxis in Euglena gracilis

• Published in: Journal of plant physiology Vol. 159; no. 8; pp. 855 - 862
• Main Authors: Streb, Christine, Richter, Peter, Ntefidou, Maria, Lebert, Michael, Häder, Donat-P.
• Format: Journal Article
• Language: English
• Published: Jena Elsevier GmbH 2002; Elsevier; Elsevier Science Ltd
• Subjects: Biological and medical sciences; calmodulin; Cell motion; Cell physiology; cyclic nucleotides; Euglena gracilis; flagellates; Fundamental and applied biological sciences. Psychology; gravitaxis; Plant physiology and development; sensory transduction; cyclic nucleotides; flagellates; gravitaxis; sensory transduction; calmodulin; Euglena gracilis; Euglenophyta; Signal transduction; Regulation(control); Algae; Taxis; Mechanism of action; Calmodulin; Thallophyta; Gravity
• ISSN: 0176-1617; 1618-1328
• DOI: 10.1078/0176-1617-00769

Euglena gracilis is a single-celled freshwater flagellate which shows, among other movement behaviors, a negative gravitaxis (cells swim upward in the water column) and a pronounced phototaxis. Gravitaxis is most likely an active physiological mechanism, and the influence of various inhibitors on the gravitaxis in
Euglena gracilis was tested using the fully automatic image analysis system ECOTOX to elucidate the possible cellular mechanism of gravity perception and signal transduction. Substances such as the phosphodiesterase inhibitors theophylline, IBM-X and forskolin, which increase the intracellular cAMP concentration, enhance the precision of graviorientation of the cells measured shortly after incubation. Indomethacin, which decreases the intracellular cAMP concentration by inhibition of the adenylate cyclase, inhibited graviorientation. All inhibitors of calmodulin metabolism tested reduced the precision of gravitaxis in
Euglena gracilis. Heparin and LiCl, which inhibit the IP
3-pathway (block IP
3 channels or formation of IP
3, respectively) had no effect. The potassium channel blockers BaCl
2 and CsCl showed an effect on the orientation behavior, while tetraethylammonium (TEA) had no influence. The protein phosphatase inhibitor, ocadaic acid, inhibited graviorientation at low concentrations. The data are discussed with respect to the current working model for gravitaxis in
Euglena gracilis