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The role of calcium in flow-stimulated bioluminescence of dinoflagellates Peter von Dassow*; MI Latz Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, 92093-0202, USA      *(pvondass@ucsd.edu) Many dinoflagellates emit bright discrete flashes of light nearly instantaneously in response to either laminar or turbulent flows as well as direct mechanical stimulation. We are interested in using dinoflagellate bioluminescence as a proxy for the initial cellular mechanotransduction events triggered by flow. Flash production is known to be mediated by a proton-mediated action potential across the vacuolar membrane, but the mechanotranduction process initiating this action potential is unknown. We report on an investigation of the role of Ca2+ in the mechanotransduction process regulating bioluminescence in the red tide dinoflagellate Lingulodinium polyedrum. Calcium ionophores and digitonin stimulated bioluminescence in a calcium-dependent manner. Several known calcium channel blockers and also gadolinium, a blocker of many stretch-activated ion channels, inhibited mechanical stimulation of bioluminescence but did not reduce luminescent capacity. Experiments with a shear flow demonstrated that flow-stimulated bioluminescence depends on the presence of extracellular calcium. Luminescent dinoflagellates are a potential model system to study how flow triggers calcium signaling in suspended cells. [Poster: vondasso.peter.89412]

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