Key features in the circadian rhythm and biochemistry of bioluminescence have
been found to differ among species. In Lingulodinium polyedrum (Stein) J. D. Dodge,
one of the best-studied species in terms of bioluminescence, cellular levels of both
luciferase and LBP fluctuate in a circadian manner. However, in others such as
Pyrocystis sp., the daily levels of luciferase remain constant and there is no LBP. This
is in contrast to L. polyedrum, in which LBP has been shown to be a necessary component
in the biochemical reaction (Knaust et al. 1998). Analysis of the full-length
luciferase from multiple species of dinoflagellates has shown that all possess a single
polypeptide comprised of an N-terminal region of unknown function followed
by three homologous domains, each possessing catalytic activity. Differences exist
among gene structure and organization such as a dramatic reduction in synonymous
substitution rates in some species, including L. polyedrum, while Pyrocystis sp. exhibit
a higher rate of synonymous substitutions that are uniform along the domains
(Liu et al. 2004).