Photomotile responses

Photoreceptor structures, dedicated to the detection of the environmental light stimuli, have been shown to be present in some known photoreactive eucaryotes, such as for instance Euglena gracilis. In other cases, such as, for example, Ochromonas danica, no information was until now available on its photomotile responses, but ultrastructural research has shown the presence of possible photoreceptor structures, as we will see below therefore, we decided to investigate whether Ochromonas showed a photomotile behavior and our preliminary results are reported in what follows. 

Single-cell photomotile responses were examined using a Leitz Ortholux II optical microscope, coupled to a Philips B/N LDH 25 videocamera equipped with a IR sensitive SIVICON LDM 4461/00 tube,... 

ScevoH, R, Bisi, E, Colombetti, G., Ghetti, E, Lenci, F., and PassareUi, V., Photomotile responses of Blepharisma Japonicum I action spectra determination and time-resolved fluorescence of photoreceptor pigments, /. Photochem. Photobiol B Biol, 1, 75,1987. 

Photomotile Responses Photoreceptor Organelles Light-Tracking Strategies 122-2... 

The investigation of the photomotile responses in these organisms requires careful attention many stimuH, in fact, are often present at the same time, so that it is necessary to be able to isolate the response relative to only one stimulus, and rule out the contribution of others. In the study of photomotile reactions, this is usuaUy done by trying to keep under control, as much as possible, aU the environmental conditions (temperature, pH, chemicals) and by varying the characteristics of Hght (fluence rate, spectral composition, polarization) at wiU. 

There is general consensus that photomotile responses can be divided into three main types ... 

To summarize what is known of the nature of the photoreceptor pigments involved in photomotile responses in ciliates, the results reported in the Hterature seem to roughly indicate three main types of photoreceptor pigments. ... 

A protein that binds radiolabeled retinal was isolated from Chlamydomonas eyespot preparations. For several years, this abundant protein in the eyespot membranes was considered the photoreceptor for photomotile responses. However, its gene-predicted primary sequence, as well as that of a similar Volvox protein, suggest two to four transmembrane helices and no homology to archaeal opsins. Moreover, recently, the so-caUed chlamyrhodopsin was ruled out as a photoreceptor pigment for phototaxis or photophobic responses in Chlamydomonas. ... 

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