Revisiting convergence: in bioluminescent enzymes (Introduction)

by David Turell , Wednesday, July 26, 2017, 16:26 (2676 days ago) @ David Turell

Glowing enzymes that are the same are found in different unrelated organisms:

http://www.the-scientist.com/?articles.view/articleNo/49850/title/The-Unlikely-Relation...

"Although the long-tentacled brittle star (Amphiura filiformis) differs from the stout sea pansy (Renilla) in both appearance and phylogeny, researchers have now demonstrated that they share a similar luciferase—an enzyme that catalyzes the light-producing reaction that results in the invertebrates’ bioluminescence.

"When an international group of researchers searched the brittle star’s genome and transcriptome for known luciferase sequences, they detected sequences in the echinoderm that were homologous to those of the luciferase of the sea pansy—a cnidarian. The sequences were so similar, in fact, that antibodies specific to the sea pansy luciferase could also detect the brittle star luciferase.  

"Conventional dogma states that every taxonomic group has its own distinct luciferase, explains lead author Jérôme Delroisse of the University of Mons; but previous work has found similar homologies in distantly related species. How such different species acquired similar luciferases remains unclear, however.

"The sea pansy’s luciferase has known homology to a nonbioluminescent bacterial enzyme, and the authors uncovered similar proteins in other nonluminous organisms. The data suggest that both brittle star and sea pansy luciferases evolved “from a common ancestral protein originally not involved in light emission,” says Delroisse, and that the gene for this protein horizontally transferred from bacteria to a common ancestor. It’s becoming clearer that “not all independently evolved bioluminescent enzymes have to be structurally different,” says Miriam Sharpe of the University of Otago who was not involved in the study."

Comment: The study's tortured explanation is an attempt to stick with standard Darwinism. There are bioluminescent bacteria that have symbiotic relationships with other organisms. Invoking horizontal transfer is an attempt to get around the issue of the size and complexity of enzymes and the improbability of chance discovery of the same molecule by chance mutation. Convergence is a theory that suggests there is an overall underlying plan for evolution, championed by Simon Conway Morris. Makes as much sense as the author's suggestion or perhaps more sense.