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1.
J Eukaryot Microbiol ; 58(2): 171-7, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-21332875

RESUMEN

Expressed rhodopsins were detected by proteomic analysis in an investigation of potential signal receptors in the cell membrane of the marine heterotrophic dinoflagellate Oxyrrhis marina (CCMP604). We inferred these to be sensory rhodopsins, a type of G-protein-coupled receptor trans-membrane signaling molecule. Because phototactic behavior based on sensory rhodopsins has been reported in other protists, we investigated the photosensory response of O. marina. This dinoflagellate exhibited strongest positive phototaxis at low levels (2-3 µE/m(2)/s) of white light when the cells were previously light adapted and well fed. Positive phototaxis was also found for blue (450 nm), green (525 nm), and red (680 nm) wavelengths. In a further test, O. marina showed significantly greater phototaxis toward concentrated algal food illuminated by blue light to stimulate red chlorophyll-a autofluorescence in the prey, compared with using bleached algae as prey. Concentration of a cytoplasmic downstream messenger molecule, cyclic adenosine monophosphate, a component of the signaling pathway of G-protein-coupled receptor molecules, rapidly increased in O. marina cells after exposure to white light. In addition, treatment with hydroxylamine, a rhodopsin signaling inhibitor, significantly decreased their phototactic response. Our results demonstrate that a heterotrophic marine dinoflagellate can orient to light based on rhodopsins present in the outer cell membrane and may be able to use photosensory response to detect algal prey based on chlorophyll autofluorescence.


Asunto(s)
Dinoflagelados/metabolismo , Dinoflagelados/efectos de la radiación , Agua de Mar/parasitología , Dinoflagelados/genética , Procesos Heterotróficos , Luz , Procesos Fototróficos , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Rodopsina/genética , Rodopsina/metabolismo , Transducción de Señal
2.
J Eukaryot Microbiol ; 55(1): 18-21, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-18251798

RESUMEN

Phagotrophic protists are major consumers of microbial biomass in aquatic ecosystems. However, biochemical mechanisms underlying prey recognition and phagocytosis by protists are not well understood. We investigated the potential roles of cell signaling mechanisms in chemosensory response to prey, and in capture of prey cells, by a marine ciliate (Uronema sp.) and a heterotrophic dinoflagellate (Oxyrrhis marina). Inhibition of protein kinase signal transduction biomolecules caused a decrease in both chemosensory response and predation. Inhibition of G-protein coupled receptor signaling pathways significantly decreased chemosensory response but had no effect on prey ingestion. Inhibitor compounds did not appear to affect general cell health, but had a targeted effect. These results support the idea that cell signaling pathways known in other eukaryotic organisms are involved in feeding behavior of free-living protists.


Asunto(s)
Cilióforos/fisiología , Dinoflagelados/fisiología , Fagocitosis/efectos de los fármacos , Agua de Mar/parasitología , Transducción de Señal/efectos de los fármacos , Animales , Apoptosis , Quimiotaxis , Cilióforos/efectos de los fármacos , Dinoflagelados/efectos de los fármacos , Inhibidores de Proteínas Quinasas/farmacología , Receptores Acoplados a Proteínas G/antagonistas & inhibidores
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