Abstracts

Bioluminescence, defined as the production of visible light by a living organism, is a fascinating phenomenon that has attracted the curiosity of scientists since antiquity. Resulting from a biochemical reaction involving a substrate (a luciferin) oxidized by a specific enzyme (the luciferase), bioluminescence sustains various ecological functions such as defense against predation, attraction of prey, and intra/interspecific communication.Light production in benthic anthozoan has been known for a long time, and particular attention was paid to the sea pansy genus, Renilla. The knowledge of the Renilla luminous system led to the extensive use of its luciferase, the so-called RLuc, as a tool for biotechnologies. Nevertheless, information on other sea pens remains scarce, notably concerning light emission control. Through morphological, transcriptomic, pharmacological, and biochemical analyses, we worked on two anthozoan sea pens, Pennatula phosphorea and Funiculina quadrangularis, living in sympatry within Swedish fjords, to shed light on their bioluminescence physiology. We highlighted (i) the conservation of the luciferase and coelenterazine requirement in the bioluminescence system among anthozoans, (ii) the expression site of the luciferase, (iii) the involvement of calcium and coelenterazine-binding protein in the light emission process, (iv) a catecholaminergic control of the light production. Besides, through the maintenance in captivity of P. phosphorea with coelenterazine-free food for a year, we demonstrated the ability of this sea pen to synthesize the coelenterazine substrate to maintain its luminous status. The two investigated species produce light in different wavelengths (i.e. green at 510 nm for P. phosphorea and blue at 485 nm for F. quadrangularis). Transcriptomic and morphological analyses pinpointed the use of a green fluorescent protein for P. phosphorea. A comparative analysis was performed with another Pennatuloidea, Anthoptilum murrayi. Although these new data unveiled the luminescence physiology and evolutive conservation of light production in sea pens, questions remain on the ecological function of the light emitted by these species.