Meeting Abstract

99-6  Saturday, Jan. 6 14:45 – 15:00  Circadian Clock Proteins in the Nudibranch Mollusks Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea. COOK, GM*; GRUEN, AE; MORRIS, J; PANKEY, MS; SENATORE, A; KATZ, PS; WATSON, WH; NEWCOMB, JM; New England College, Henniker, NH; University of New Hampshire, Durham; New England College, Henniker, NH; University of New Hampshire, Durham; University of Toronto, Mississauga, ON; University of Massachusetts, Amherst; University of New Hampshire, Durham; New England College, Henniker, NH gcook@nec.edu http://www.nec.edu/

While many studies have reported on the molecular clocks underlying circadian rhythms in vertebrates and ecdysozoan invertebrates, such as arthropods, much less is known about these clocks in lophotrocozoan invertebrates. The goal of this project was to identify the RNA and protein products of putative clock genes in the central nervous system of three nudibranchs, Hermissenda crassicornis, Melibe leonina, and Tritonia diomedea. Using transcriptomics, we identified orthologs in each species for the products of five canonical clock genes: bmal1, clock, non-photoreceptive cryptochrome, period, and timeless. Orthologous sequences for the products of four related genes—photoreceptive cryptochrome, cryptochrome DASH, 6-4 photolyase, and timeout—were also recovered. All of the resulting nudibranch proteins contained conserved functional domains found in their orthologs in other species. Phylogenetic analyses indicated that the nudibranch proteins were most closely related to the limited examples in other lophotrochozoan groups. A clock-related gene repertoire in the nudibranchs that includes both timeless and timeout, as well as both photoreceptive and non-photoreceptive cryptochromes, resembles what is seen in non-drosopholid insects and oysters, and may represent the ancestral circadian clock for bilaterians.