Photophobic responses and phototaxis in <i>Chlamydomonas</i> are triggered by a single rhodopsin photoreceptor

Kröger, Petra; Hegemann, Peter

doi:10.1016/0014-5793(94)80229-7

Cited by 32 publications

(21 citation statements)

References 22 publications

(14 reference statements)

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“…All-trans retinal and alltrans retinol are by far the most dominant retinoids in whole cells and in putative eyespot membranes. In general, the data suggest that the photoreceptor for both behavioural responses is the same rhodopsin with an all-trans retinal chromophore which is activated by an all-trans to 13-cis isomerization (Kroger and Hegemann, 1994; Zacks and Spudich, 1994).…”

Section: Introductionmentioning

confidence: 88%

Chlamyrhodopsin represents a new type of sensory photoreceptor.

et al. 1995

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In order to find optimal light conditions for photosynthetic growth, the green alga Chlamydomonas uses a visual system. An optical device, a rhodopsin photoreceptor and an electrical signal transduction chain that mediates between photoreceptor and flagella comprise this system. Here we present an improved strategy for the preparation of eyespot membranes. These membranes contain a retinal binding protein, which has been proposed to be the apoprotein of the phototaxis receptor. The retinal binding protein, which we named chlamyopsin, was purified and opsin‐specific antibodies were raised. Using these antibodies, the opsin was localized in the eyespot region of whole cells during growth and cell division. The opsin cDNA was purified and sequenced. The sequence reveals that chlamyopsin is not a typical seven helix receptor. It shows some homology to invertebrate opsins but not to opsins from halobacteria. It contains many polar and charged residues and might function as a light‐gated ion channel complex. It is likely that this lower plant rhodopsin diverged from animal opsins early in opsin evolution.

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Section: Introductionmentioning

confidence: 88%

Chlamyrhodopsin represents a new type of sensory photoreceptor.

et al. 1995

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“…The most extensively studied chlorophycian member, ChIamydomonas reinhardtii, exhibits similar action spectra for positive and negative phototaxis at the visible region (Nultsch et al 1971); however, the action spectrum at the UV-B/C region was not yet reported. Because the involvement of a rhodopsin-like photoreceptor was demonstrated in the latter organism (Foster et al 1984, Takahashi et al 1991, Lawson et al 1991, Kr6ger and Hegemann 1994, Kreimer 1994, Deininger etal. 1995, it is interesting that the result in Tetraselmis suggests the possibility that the signaling effect of UV-B/C light is observable not only in the UV-A/blue-type responses but also in the green-light-type response mediated by rhodopsin.…”

Section: The Signaling Effect Of the Uv-b/c Lightmentioning

confidence: 98%

Discovery of signaling effect of UV-B/C light in the extended UV-A/blue-type action spectra for step-down and step-up photophobic responses in the unicellular flagellate algaEuglena gracilis

et al. 1998

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Summary. Cultures of unicellular algal flagellate Euglena gracilisgrown in different conditions were subjected to action spectroscopy for step-down and step-up photophobic responses, respectively. The spectral region was extended into the UV-B/C as well as in the UV-A and visible regions with the Okazaki Large Spectrograph as the monochromatic light source. The photophobic responses of the cells were measured with an individual-cell assay method with the aid of a computerized video motion analyzer. In the UV-A and visible regions, the shapes of the action spectra were the so-called UV-A/blue type. In the newly studied UV-B/C region, new action peaks were found at 270 nm for the step-down response and at 280 nm for the step-up one. The absorption spectrum of flavin adenine dinucleotide (FAD) appeared to fit the action spectrum for the stepup response, whereas the shape of the step-down action spectrum, which has a UV-A peak (at 370 nm) higher than the blue peak (at 450 rim), appeared to be mimicked by the absorption spectrum of a mixed solution of 6-biopterin and FAD. These observations might also account for the fact that the UV-B/C peak wavelength at 270 nm of the action spectrum for the step-down response is shorter by 10 nm than the action spectrum for the step-up response at 280 nm.

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“…The deduced protein sequence is 61% identical to chlamyopsin if aligned without gaps (Figure 2), and it definitely belongs to the same algal opsin family. Chlamyopsin is the only detectable retinal binding protein in the unicellular flagellate alga C. reinhardtii (Kröger and Hegemann, 1994) and the most abundant protein in eyespot preparations of this species (Deininger et al, 1995). Chlamyopsin and the encoded opsinlike V. carteri protein are 89% similar between residues 69 and 205, whereas they differ significantly at their N termini and considerably more at their C termini.…”

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confidence: 99%

Volvoxrhodopsin, a Light-Regulated Sensory Photoreceptor of the Spheroidal Green Alga Volvox carteri

et al. 1999

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Somatic cells of the multicellular alga Volvox carteri contain a visual rhodopsin that controls the organism's phototactic behavior via two independent photoreceptor currents. Here, we report the identification of an opsinlike gene, designated as volvoxopsin ( vop ). The encoded protein exhibits homologies to the opsin of the unicellular alga Chlamydomonas reinhardtii (chlamyopsin) and to the entire animal opsin family, thus providing new perspectives on opsin evolution. Volvoxopsin accumulates within the eyes of somatic cells. However, the vop transcript is detectable only in the reproductive eyeless gonidia and embryos. vop mRNA levels increase 400-fold during embryogenesis, when embryos develop in darkness, whereas the vop transcript does not accumulate when embryos develop in the light. An antisense transformant, T3, was generated. This transformant produces 10 times less volvoxopsin than does the wild type. In T3, the vop transcript is virtually absent, whereas the antisense transcript is predominant and light regulated. It follows that vop expression is under light-dependent transcriptional control but that volvoxopsin itself is not the regulatory photoreceptor. Transformant T3 is phototactic, but its phototactic sensitivity is reduced 10-fold relative to the parental wild-type strain HK10. Thus, we offer definitive genetic evidence that a rhodopsin serves as the photoreceptor for phototaxis in a green alga. INTRODUCTIONVolvox carteri is a simple spheroidal multicellular alga with many features that recommend it as a model for studying the process of cytodifferentiation (Kirk and Harper, 1986) and the development of photoreception in lower eukaryotes. Individuals of this species contain only two distinct cell types-16 large reproductive cells (gonidia) and 2000 to 4000 somatic cells that cannot divide. The somatic cells are arranged in a single layer at the surface of the transparent sphere, whereas the 16 gonidia are located below the surface, where they have no direct contact with the external medium (Kirk et al., 1991). All somatic cells are biflagellate and possess eyespots, which, together with the photoreceptor and the downstream signaling machinery, form the functional eye. The eyes are responsible for guiding the organism to places of optimal light conditions. The orientation of the individual somatic cells within the spheroid combined with the three-dimensional pattern in which their flagella beat cause the spheroid to rotate in a counterclockwise direction as it moves (Hoops, 1993). The two flagella of each cell beat synchronously and in an almost precisely parallel fashion, but they beat toward the posterior of the spheroid and slightly to the right, causing the spheroid to rotate to the left as it moves forward (Hoops, 1993(Hoops, , 1997. Anterior cells possess larger and more sensitive eyes than do posterior ones (Sakaguchi and Iwasa, 1979; Hoops, 1997).In V. carteri , the photophobic response involves a cessation of flagellar movement (on-off response) and not a switch to a different beati...

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Photophobic responses and phototaxis in Chlamydomonas are triggered by a single rhodopsin photoreceptor

Cited by 32 publications

References 22 publications

Chlamyrhodopsin represents a new type of sensory photoreceptor.

Chlamyrhodopsin represents a new type of sensory photoreceptor.

Discovery of signaling effect of UV-B/C light in the extended UV-A/blue-type action spectra for step-down and step-up photophobic responses in the unicellular flagellate algaEuglena gracilis

Volvoxrhodopsin, a Light-Regulated Sensory Photoreceptor of the Spheroidal Green Alga Volvox carteri

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