CALCIUM RELEASE FROM INTRACELLULAR STORES IS NECESSARY FOR THE PHOTOPHOBIC RESPONSE IN THE BENTHIC DIATOM NAVICULA PERMINUTA (BACILLARIOPHYCEAE)1

Complex photoreceptor pathways exist algae to exploit light as a sensory stimulus. Previous studies have implicated calcium blue-light signaling plants and algae. A photophobic response to high-intensity blue light was characterized the marine benthic diatom Navicula perminuta (Grunow) van Heurck. Calcium modulators were used to determine the involvement of calcium the signaling of this response, and the fluorescent calcium indicator Calcium Crimson was used to image changes intracellular [Ca 2+] 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 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 average cell speed. As the increase intracellular [Ca 2+] at the cell tip corresponded to the time of direction change rather than the onset of the light stimulus, it would appear that Ca 2+ constitutes a component of the switching mechanism that leads to reversal of the locomotion machinery. Our current evidence suggests that the source of this Ca 2+ is intracellular. © 2012 Phycological Society of America.