title: The abundant retinal protein of the Chlamydomonas eye is not the photoreceptor for phototaxis and photophobic responses.
abstract: The chlamyopsin gene (cop) encodes the most abundant eyespot protein in the unicellular green alga Chlamydomonas reinhardtii. This opsin-related protein (COP) binds retinal and was thought to be the photoreceptor controlling photomovement responses via a set of photoreceptor currents. Unfortunately, opsin-deficient mutants are not available and targeted disruption of non-selectable nuclear genes is not yet possible in any green alga. Here we show that intron-containing gene fragments directly linked to their intron-less antisense counterpart provide efficient post-transcriptional gene silencing (PTGS) in C. reinhardtii, thus allowing an efficient reduction of a specific gene product in a green alga. In opsin-deprived transformants, flash-induced photoreceptor currents (PC) are left unchanged. Moreover, photophobic responses as studied by motion analysis and phototaxis tested in a light-scattering assay were indistinguishable from the responses of untransformed wild-type cells. We conclude that phototaxis and photophobic responses in C. reinhardtii are triggered by an as yet unidentified rhodopsin species.
authors.affiliation: Institut für Biochemie I, Universität Regensburg, 93040 Regensburg, Germany. markus.fuhrmann@vkl.uni-regensburg.de
authors.forename: M
authors.initials: M
authors.lastname: Fuhrmann
authors.forename: A
authors.initials: A
authors.lastname: Stahlberg
authors.forename: E
authors.initials: E
authors.lastname: Govorunova
authors.forename: S
authors.initials: S
authors.lastname: Rank
authors.forename: P
authors.initials: P
authors.lastname: Hegemann
mesh_terms: D020418:Algal Proteins; D000818:Animals; D001059:Apoproteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D020868:Gene Silencing; D047908:Intracellular Signaling Peptides and Proteins; D008027:Light; D010786:Photoreceptor Cells / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000032:analysis; D016337:RNA, Catalytic; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D012160:Retina / Q000378:metabolism*; D017299:Rod Opsins / Q000378:metabolism*; D014170:Transformation, Genetic
chemical_list: D020418:Algal Proteins; D001059:Apoproteins; D002352:Carrier Proteins; D005136:Eye Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015800:Protozoan Proteins; D016337:RNA, Catalytic; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D017299:Rod Opsins; C097338:chlamyopsin protein, Chlamydomonas reinhardtii; C418481:hairpin ribozyme; D012313:RNA