The involvement of a protein kinase in phototaxis and gravitaxis of Euglena gracilis
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The unicellular flagellate Euglena gracilis shows positive phototaxis at low-light intensities (<10 W/m2) and a negative one at higher irradiances (>10 W/m2). 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.
KeywordsEuglena Gravitaxis Phototaxis Protein kinase Signal transduction
Photoactivated adenylyl cyclase
Rapid amplification of cDNA ends
The authors gratefully acknowledge the skillful technical assistance of Jennifer Tebart, Ulrike Trenz and Martin Schuster.
- Checcucci A, Colombetti G, Ferrara R, Lenci F (1976) Further analysis of the mass photoresponses of Euglena gracilis Klebs (Flagellata euglenoidina). Monitore Zool Ital N S 10:271–277Google Scholar
- Lebert M, Häder D-P (1999) Image analysis: a versatile tool for numerous applications. G I T Imaging Microsc 1:5–6Google Scholar
- Merchant SS, Prochnik SE, Vallon O, Harris EH, Karpowicz SJ, Witman GB, Terry A, Salamov A, Fritz-Laylin LK, Maréchal-Drouard L, Marshall WF, Qu L-H, Nelson DR, Sanderfoot AA, Spalding MH, Kapitonov VV, Ren Q, Ferris P, Lindquist E, Shapiro H, Lucas SM, Grimwood J, Schmutz J, Cardol P, Cherutti H, Chanfreau G, Chen C-L, Cognat V, Croft MT, Dent R, Dutcher S, Fernández E, Fukuzawa H, González-Ballester D, González-Halphen D, Hallmann A, Hanikenne M, Hippler M, Inwood W, Jabbari K, Kalanon M, Kuras R, Lefebvre PA, Lemaire SD, Lobanov AV, Lohr M, Manuell A, Meier I, Mets L, Mittag M, Mittelmeier T, Moroney JV, Moseley J, Napoli C, Nedelcu AM, Niyogi K, Novoselov SV, Paulsen IT, Pazour G, Purton S, Ral J-P, Riaño-Pachón DM, Riekhof W, Rymarquis L, Schroda M, Stern D, Umen J, Willows R, Wilson N, Zimmer SL, Allmer J, Balk J, Bisova K, Chen C-J, Elias M, Gendler K, Hauser C, Lamb MR, Ledford H, Long JC, Minagawa J, Page MD, Pan J, Pootakham W, Roje S, Rose A, Stahlberg E, Terauchi AM, Yang P, Ball S, Bowler C, Dieckmann CL, Gladyshev VN, Green P, Jorgensen R, Mayfield S, Mueller-Roeber B, Rajamani S, Sayre RT, Brokstein P, Dubchak I, Goodstein D, Hornick L, Huang YW, Jhaveri J, Luo Y, Martínez D, Ngau WCA, Otillar B, Poliakov A, Porter A, Szajkowski L, Werner G, Zhou K, Grigoriev IV, Rokhsar DS, Grossman AR (2007) The Chlamydomonas genome reveals the evolution of key animal and plant functions. Science 318:245–250PubMedCentralPubMedCrossRefGoogle Scholar
- Richter P, Häder D-P (2000) Calcium imaging in living cells. In: Häder D-P (ed) Image analysis: methods and applications. CRC Press, Boca Raton, pp 373–389Google Scholar
- Richter PR, Streb C, Ntefidou M, Lebert M, Häder D-P (2003) High light-induced sign change of gravitaxis in the flagellate Euglena gracilis is mediated by reactive oxygen species. Acta Protozool 42:197–204Google Scholar
- Schlösser UG (1994) SAG-Sammlung von Algenkulturen at the University of Göttingen. Catalogue of Strains 1994. Bot Acta 107:113–186Google Scholar
- Schmidt M, Geßner G, Luff M, Heiland I, Wagner V, Kaminski M, Geimer S, Eitzinger N, Reißenweber T, Voytsekh O, Fiedler M, Mittag M, Kreimer G (2006) Proteomic analysis of the eyespot of Chlamydomonas reinhardtii provides novel insights into its components and tactic movements. Plant Cell 18:1908–1930PubMedCentralPubMedCrossRefGoogle Scholar
- Tahedl H, Richter P, Lebert M, Häder D-P (1998) cAMP is involved in gravitaxis signal transduction of Euglena gracilis. Microgravity Sci Technol 11:173–178Google Scholar
- Vogel K, Häder D-P (1990) Simultaneous tracking of flagellates in real time by image analysis. In: Proc Fourth European Symposium on Life Science Research in Space (ESA SP-307), pp 541–545Google Scholar