CALCIUM RELEASE FROM INTRACELLULAR STORES IS NECESSARY FOR THE PHOTOPHOBIC RESPONSE IN THE BENTHIC DIATOM NAVICULA PERMINUTA (BACILLARIOPHYCEAE)1 |
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Authors: | Graham J C Underwood Colin Brownlee |
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Institution: | 1. Department of Biological Sciences, University of Essex, Colchester, CO7 3SQ, UK;2. Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB, UK |
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Abstract: | Complex photoreceptor pathways exist in algae to exploit light as a sensory stimulus. Previous studies have implicated calcium in blue‐light signaling in plants and algae. A photophobic response to high‐intensity blue light was characterized in the marine benthic diatom Navicula perminuta (Grunow) in van Heurck. Calcium modulators were used to determine the involvement of calcium in the signaling of this response, and the fluorescent calcium indicator Calcium Crimson was used to image changes in intracellular Ca2+] during a response. A localized, transient elevation of Calcium Crimson fluorescence was seen at the cell tip at the time of cell reversal. Intracellular calcium release inhibitors produced a significant decrease in the population photophobic response. Treatments known to decrease influx of extracellular calcium had no effect on the population photophobic response but did cause a significant decrease in average cell speed. As the increase in intracellular Ca2+] at the cell tip corresponded to the time of direction change rather than the onset of the light stimulus, it would appear that Ca2+ constitutes a component of the switching mechanism that leads to reversal of the locomotion machinery. Our current evidence suggests that the source of this Ca2+ is intracellular. |
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Keywords: | blue light calcium diatom motility signaling |
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