Pharmacological investigation of the bioluminescence signaling pathway of the dinoflagellate Lingulodinium polyedrum: evidence for the role of stretch‐activated ion channels

Abstract

Dinoflagellate bioluminescence serves as a whole-cell reporter of mechanical stress, which activates a signaling pathway that appears to involve the opening of voltage-sensitive ion channels and release of calcium from intracellular stores. However, little else is known about the initial signaling events that facilitate the transduction of mechanical stimuli. In the present study using the red tide dinoflagellate Lingulodinium polyedrum (Stein) Dodge, two forms of dinoflagellate bioluminescence, mechanically stimulated and spontaneous flashes, were used as reporter systems to pharmacological treatments that targeted various predicted signaling events at the plasma membrane level of the signaling pathway. Pretreatment with 200 μM Gadolinium III (Gd(3+) ), a nonspecific blocker of stretch-activated and some voltage-gated ion channels, resulted in strong inhibition of both forms of bioluminescence. Pretreatment with 50 μM nifedipine, an inhibitor of L-type voltage-gated Ca(2+) channels that inhibits mechanically stimulated bioluminescence, did not inhibit spontaneous bioluminescence. Treatment with 1 mM benzyl alcohol, a membrane fluidizer, was very effective in stimulating bioluminescence. Benzyl alcohol-stimulated bioluminescence was inhibited by Gd(3+) but not by nifedipine, suggesting that its role is through stretch activation via a change in plasma membrane fluidity. These results are consistent with the presence of stretch-activated and voltage-gated ion channels in the bioluminescence mechanotransduction signaling pathway, with spontaneous flashing associated with a stretch-activated component at the plasma membrane.

Microalgae: Current Research and Applications

“…The action potential produced by these processes leads to an influx of protons from the acidic vacuole into the scintillons that protrude into the acidic vacuole, decreasing their internal pH from ~8 to ~6 (Fogel & Hastings, 1972). Voltage gated proton channels are involved in this process (Jin et al, 2013), presumably such as that recently characterized in another (nonbioluminescent) dinoflagellate (Smith et al, 2011). Recently, a role for stretch activated ion channels has also been revealed.…”

“…Meanwhile, in the field, bioluminescence has been used to study ecological dynamics within the plankton and to monitor toxic blooms (Moline et al, 2009;Shulman et al, 2011;Le Tortorec et al, 2013). Studies on dinoflagellate bioluminescence have shed like on fundamental processes like cellular mechanotransduction (von Dassow & Latz, 2002;Chen et al, 2007;Jin et al, 2013), circadian rhythms (Hastings, 2009) and evolution of gene structure (Liu et al, 2004;Liu & Hastings, 2007). The molecular components of the reaction have been used as reporters in biomedical applications (Suzuki et al, 2005;Li et al, 2010) and whole cells have been used to visualize fluid flow (Rohr et al, 2002;Watanabe & Tanaka, 2011).…”

“…Recently, a role for stretch activated ion channels has also been revealed. These are activated by changes in the fluidity of the plasma membrane, for example by shear stress, which has now been shown to be the primary self-stimulator of spontaneous bioluminescence (Jin et al, 2013).…”

Analysis of Statoliths Displacement in Chara Rhizoids for Validating the Microgravity-Simulation Quality of Clinorotation Modes

“…Clear evidence for the negative impact of the real-random mode on cellular activities comes from experiments with the fast and sensitive shear stress reporter system of dinoflagellates (Hauslage et al 2017). Shear stress and hydrodynamic gradients trigger a luciferin/luciferase reaction in dinoflagellates probably via a calcium mediated signaling cascade (Mallipattu et al 2002;Jin et al 2013;Von Dassow and Latz 2002). Bioluminescence is part of the defense mechanism of these dinoflagellates.…”

The artistry of dinoflagellate bioluminescence

“…The entire pathway, from mechanical stimulation to light production, is extremely rapid with a duration of less than 20 ms [7,11,12]. Our current research is investigating the signaling proteins involved in this pathway, in the process identifying elements of mechanical sensing that have been conserved in higher organisms [13].…”