This Article Full Text Full Text (PDF) All Versions of this Article: 133/4/1517    most recent pp.103.034223v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Physiol. Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Web of Science (28) Citing Articles via Google Scholar Google Scholar Articles by Ntefidou, M. Articles by Häder, D.-P. Search for Related Content PubMed PubMed Citation Articles by Ntefidou, M. Articles by Häder, D.-P. Agricola Articles by Ntefidou, M. Articles by Häder, D.-P.

Photoactivated Adenylyl Cyclase Controls Phototaxis in the Flagellate Euglena gracilis

Department of Plant Ecophysiology, Friedrich-Alexander University, Staudtstrasse 5, 91058 Erlangen, Germany (M.N., M.L., D.-P.H.); National Institute for Basic Biology, Okazaki, Aichi, 444-8585 Japan (M.I., M.W.); Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi Saitama, 332-0012 Japan (M.I.); and Department of Photoscience, School of Advanced Sciences, Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa, 240-0193 Japan (M.W.)

Euglena gracilis, a unicellular freshwater protist exhibits different photomovement responses, such as phototaxis (oriented movement toward or away from the light source) and photophobic (abrupt turn in response to a rapid increase [step-up] or decrease [step-down] in the light fluence rate) responses. Photoactivated adenylyl cyclase (PAC) has been isolated from whole-cell preparations and identified by RNA interference (RNAi) to be the photoreceptor for step-up photophobic responses but not for step-down photophobic responses (M. Iseki, S. Matsunaga, A. Murakami, K. Ohno, K. Shiga, C. Yoshida, M. Sugai, T. Takahashi, T. Hori, M. Watanabe [2002] Nature 415: 1047-1051). The present study shows that knockdown of PAC by RNAi also effectively suppresses both positive and negative phototaxis, indicating for the first time that PAC or a PAC homolog is also the photoreceptor for photoorientation of wild-type E. gracilis. Recovery from RNAi occurred earlier for step-up photophobic responses than for positive and negative phototaxis. In addition, we investigated several phototaxis mutant strains of E. gracilis with different cytological features regarding the stigma and paraxonemal body (PAB; believed to be the location for the phototaxis photoreceptor) as well as Astasia longa, a close relative of E. gracilis. All of the E. gracilis mutant strains had PAC mRNAs, whereas in A. longa, a different but similar mRNA was found and designated AlPAC. Consistently, all of these strains showed no phototaxis but performed step-up photophobic responses, which were suppressed by RNAi of the PAC mRNA. The fact that some of these strains possess a cytologically altered or no PAB demonstrates that at least in these strains, the PAC photoreceptor responsible for the step-up photophobic responses is not located in the PAB.

^* Corresponding author; e-mail dphaeder{at}biologie.uni-erlangen.de; fax 49-9131-852-8215.

Received October 2, 2003; returned for revision October 7, 2003; accepted October 9, 2003.

Related articles in Plant Physiol.:

Light Signaling

Edgar P. Spalding
Plant Physiol. 2003 133: 1417-1419. [Full Text]  

This article has been cited by other articles:

				G. Jekely Evolution of phototaxis Phil Trans R Soc B, October 12, 2009; 364(1531): 2795 - 2808. [Abstract] [Full Text] [PDF]

				V. Gradinaru, K. R. Thompson, F. Zhang, M. Mogri, K. Kay, M. B. Schneider, and K. Deisseroth Targeting and Readout Strategies for Fast Optical Neural Control In Vitro and In Vivo J. Neurosci., December 26, 2007; 27(52): 14231 - 14238. [Full Text] [PDF]