Two components of photoreceptor potential in phototaxis of the flagellated green alga Haematococcus pluvialis

Sineshchekov, Oleg A.; Litvin, F. F.; Keszthelyi, L.

doi:10.1016/s0006-3495(90)82504-2

Cited by 69 publications

(64 citation statements)

References 12 publications

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“…Analyses by suction pipette techniques support the hypothesis of Nultsch (1983) that excitation of rhodopsin triggers rapid opening of Ca z+ channels in the plasma membrane region of the eyespot apparatus, which in turn initiates signal spread towards the flagella (Litvin et al, 1978;Harz & Hegemann, 1991). The fast photoreceptor current consists of at least two components, which have been correlated with early and late receptor potentials in vision (Sineshchekov et al, 1990). Key factors in the visual transduction cascades of vertebrates and invertebrates * To whom correspondence and offprint requests should be addressed.…”

Section: Introductionmentioning

confidence: 68%

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Schlicher¹,

Lindén²,

Calenberg³

et al. 1995

European Journal of Phycology

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Knowledge about possible elements involved in signal transduction and adaptational phenomena during phototaxis of flagellate green algae is limited. In order to identify such putative elements we present here: (i) the isolation and characterisation of an enriched plasma membrane fraction of Spermatozopsis similis, and (ii) a comparison of the distribution of Ca2+-dependent putative kinases and G proteins, as recognised by antibodies directed against mammalian Gc~-subunits, in the plasma membrane preparation and isolated eyespot apparatuses of this green alga. In western blot analyses a 54 kDa protein reacted with an antiserum against a conserved sequence of G protein c~-subunits (anti-c~ common). A 43 kDa protein was recognised by a serum against the G~-subunit of transducin. These proteins were enriched in the eyespot fraction and to a lesser extent in the plasma membrane fraction. Two polyclonal antisera against C-terminal peptides of animal G(~-subunits also labelled a 43 kDa and 54 kDa protein in the eyespot preparations. Additionally, four putative Ca2+-dependent kinases or their catalytic subunits (47, 48, 77 and 82 kDa) were identified in the plasma membrane fraction by a gel kinase assay following electrophoretic separation. The 82 kDa protein was specifically enriched in the plasma membrane fraction, while the other putative kinases were also enriched in the eyespot fraction but not in other subcellutar fractions. Monoclonal antibodies directed against a soybean CaZ+-dependent protein kinase cross-reacted with a 6I kDa protein in the plasma membrane and a 60 kDa protein in the soluble fraction. Only a very faint response was observed in the fraction enriched in eyespot apparatuses. Our results indicate (i) a low cross-contamination of the eyespot apparatus preparation by normal plasma membrane constituents and (ii) the regulatory potential for the identified kinases and G proteins in blue/green-light-dependent photoresponses of Spermatozopsis similis.

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Section: Introductionmentioning

confidence: 68%

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Schlicher¹,

Lindén²,

Calenberg³

et al. 1995

European Journal of Phycology

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“…CSRA generates a faster photoreceptor current that saturates at high light intensities, and CSRB generates a slower (delayed) current, saturating at much lower intensities. Superposition of the CSRA-and CSRBgenerated currents gives rise to the complex electrical response described in wild-type cells (9,13). Analysis of the currents in RNAi transformants, which allowed assigning specific currents to CSRA and CSRB, has made clear the relationship between the kinetic components of the current and the saturation phases of the fluence-response curve, which was difficult to resolve in the wild type (18).…”

Section: Discussionmentioning

confidence: 99%

“…Photoreceptor current generation is the earliest detected consequence of light absorption by the phototaxis-receptor molecules, occurring Ͻ3 s after a laser flash (9,13). The localization of the current to the eyespot region of the cell corresponds to the expected location of the pigments (10,11), and its action spectrum measured in vivo matches that of phototaxis (8) and of the photophobic response (14).…”

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confidence: 99%

Two rhodopsins mediate phototaxis to low- and high-intensity light in Chlamydomonas reinhardtii

Sineshchekov

Jung

Spudich

2002

Proc. Natl. Acad. Sci. U.S.A.

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513

437

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We demonstrate that two rhodopsins, identified from cDNA sequences, function as low-and high-light-intensity phototaxis receptors in the eukaryotic alga Chlamydomonas reinhardtii. Each of the receptors consists of an Ϸ300-residue seven-transmembrane helix domain with a retinal-binding pocket homologous to that of archaeal rhodopsins, followed by Ϸ400 residues of additional membraneassociated portion. The function of the two rhodopsins, Chlamydomonas sensory rhodopsins A and B (CSRA and CSRB), as phototaxis receptors is demonstrated by in vivo analysis of photoreceptor electrical currents and motility responses in transformants with RNA interference (RNAi) directed against each of the rhodopsin genes. The kinetics, fluence dependencies, and action spectra of the photoreceptor currents differ greatly in transformants in accord with the relative amounts of photoreceptor pigments expressed. The data show that CSRA has an absorption maximum near 510 nm and mediates a fast photoreceptor current that saturates at high light intensity. In contrast, CSRB absorbs maximally at 470 nm and generates a slow photoreceptor current saturating at low light intensity. The relative wavelength dependence of CSRA and CSRB activity in producing phototaxis responses matches precisely the wavelength dependence of the CSRA-and CSRB-generated currents, demonstrating that each receptor mediates phototaxis. The saturation of the two photoreceptor currents at different light fluence levels extends the range of light intensity to which the organism can respond. Further, at intensities where both operate, their light signals are integrated at the level of membrane depolarization caused by the two photoreceptor currents.retinal protein ͉ photoreceptor ͉ receptor currents ͉ signal transduction U nicellular flagellate algae optimize their light environment by motility responses. Phototaxis (or oriented movement) guides them toward or away from a light source, whereas photophobic responses prevent their crossing a light͞dark border (1). In Chlamydomonas reinhardtii these photomotility responses are mediated by retinal-containing receptor(s), as shown by retinal reconstitution studies in blind mutants (2-5). Moreover, it has been established that the native chromophore of the photoreceptor protein(s) is 6-s-trans all-trans-retinal, as in archaeal rhodopsins, and its alltrans͞13-cis isomerization is required for triggering behavioral responses (3,4,6).A complex photoreceptor apparatus is used to track the light source. The photoreceptor molecules appear to be localized in a small portion of the plasma membrane overlying the eyespot. Light absorption͞reflection by the eyespot modulates the photoreceptor illumination during helical swimming if the helix axis does not coincide with the light direction (7). This modulated illumination serves as a signal for the correction of the swimming path.A cascade of electrical phenomena plays a key role in the signal transduction. Photoexcitation of the receptor molecules results in the generation of photoreceptor...

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“…The onset of the photoreceptor current occurs within 30 ps after the flash stimulus, which is the time resolution of the recording equipment (Sineshchekov et al, 1990;Holland et al, 1996). This is significantly less than the delay times of rhodopsinmediated membrane conductance changes found in animal photoreceptors, and far less than those typical for electric responses in other plant cells.…”

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confidence: 95%

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

1997

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Photoexcitation of rhodopsin in Chlamydomonas reinhardtii triggers a complex of rapid bioelectric processes in the cell membrane. Photoreceptor and flagellar currents are the major components of this cascade and are the basis for the phototaxis and photoshock response, respectively. Desensitization and dark recovery of the extracellularly recorded photoreceptor current were investigated in double-flash excitation experiments. l h e data obtained show that the desensitization is determined by membrane depolarization rather than by rhodopsin bleaching. At external K+ concentrations less than 0.6 mM, generation of the flagellar current triggers a transient, depolarization-activated K+ efflux that contributes to membrane repolarization after light excitation. Acceleration of the dark recovery at 5 to 10 mM Ca2+ can be partially attributed to a blockade of K+ influx, which is triggered at higher external K+ concentrations. K+ currents constitute a nove1 component of the rhodopsin-mediated signaling system in C. reinhardtii that is involved in the process of dark adaptation of the system.

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Two components of photoreceptor potential in phototaxis of the flagellated green alga Haematococcus pluvialis

Cited by 69 publications

References 12 publications

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Two rhodopsins mediate phototaxis to low- and high-intensity light in Chlamydomonas reinhardtii

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

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Two components of photoreceptor potential in phototaxis of the flagellated green alga Haematococcus pluvialis

Cited by 69 publications

References 12 publications

G proteins and Ca2+-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca2+-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

Two rhodopsins mediate phototaxis to low- and high-intensity light in Chlamydomonas reinhardtii

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

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G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)

G proteins and Ca²⁺-modulated protein kinases of a plasma membrane-enriched fraction and isolated eyespot apparatuses ofSpermatozopsis similis(chlorophyceae)