FLOW‐INDUCED CHANGES IN DINOFLAGELLATE MEMBRANE FLUIDITY

Latz, M. I. 1 , von Dassow, P. 1 , Mallipatt, S. 2 , Haiddeker, M. 2 & Frangos, J. 21 Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093‐0202 USA; 2 Department of Bioengineering, University of California San Diego, San Diego, CA 92093 USA Dinoflagellates are among the most flow‐sensitive organisms known, with physiological responses including changes in swimming, population growth, morphology, and the stimulation of bioluminescence. The mechanotransduction pathways involved in flow sensing by dinoflagellates are unknown. Studies of flow‐sensitive mammalian cells have suggested that the plasma membrane is a primary mechanosensor and that flow‐induced changes in membrane fluidity activate signal transduction pathways. In the present study, flow‐induced changes in membrane fluidity of the dinoflagellate, Lingulodinium polyedrum, were monitored using the dye DCVJ (9‐(dicyanovinyl)‐julolidine), which has a fluorescence yield that is proportional to viscosity. Flow exposure resulted in a reversible decrease in DCVJ fluorescence consistent with an increase in membrane fluidity. The change in fluorescence occurred on the time scale of seconds suggesting it was not due to changes in the cytoskeleton. The magnitude of fluorescence decrease was proportional to flow rate as previously described for mammalian endothelial cells. The similar flow‐induced changes in membrane fluidity for dinoflagellates and mammalian cells suggest shared mechanotransduction mechanisms.