Meeting Abstract
P1.163 Friday, Jan. 4 Origin of luciferase genes in cypridinid ostracods (Crustacea) LEUNG, N.L.*; TAKETA, D.A.; TORRES, E.; OAKLEY, T.H.; UCSB; UCSB; California State Univ. Los Angeles; UCSB nleung@lifesci.ucsb.edu
How new features originate is a central question in evolutionary biology, but the molecular changes that lead to evolutionary novelty are difficult to surmise. Our goal is to identify the molecular changes that gave rise to bioluminescence in cypridinid ostracods. Bioluminescence is a convenient system for understanding the molecular basis of origins because biochemical assays of protein function are tractable. Cypridinid bioluminescence occurs when light-reaction catalyzing enzymes (luciferases) are secreted from the upper lip, a glandular structure above the mouth also involved in digestion. To date, only two luciferases are described in cypridinid ostracods, even though bioluminescence is present in approximately 100 species in the family. Here, we obtain sequences similar to known luciferases from 454 transcriptomes of a luminescent and a non-luminescent cypridinid species. We confirm luciferase function of a gene from the luminescent species Vargula tsujii by expressing the protein in cell culture and performing a light reaction assay. Amino acid sequence comparisons of Vargula tsujii luciferase indicate only 47% sequence identity to known luciferases from V. hilgendorfii and Cypridina noticula. We confirm that all three cypridinid luciferases contain two von Willebrand Factor type D (vWF-D) domains. We next analyzed a 454 transcriptome of non-bioluminescent cypridinid Skogsbergia lerneri and found several genes with single vWF-D domains. We hypothesize that cypridinid luciferase originated by duplication of vWF-D containing digestive proteins secreted from the upper lip of non-luminescent ostracods. We also hypothesize that subsequent duplication of the vWF-D domains itself increased efficiency of the light reaction. Future research will localize expression of vWF-D genes in the non-luminescent species, and test efficiency of their light reaction in in vitro assays.
