Meeting Abstract
Carbonic anhydrase (CA) is a metalloenzyme responsible for catalyzing the reversible hydration of carbon dioxide into bicarbonate. The CA-gene superfamily consists of five unique families (that arose independently from one another), with vertebrate and invertebrate lineages occupying the alpha-CA family. Although the original function of &alpha-CAs appears to have been as a pH regulator, due to its ability to regulate bicarbonate production, it has also been co-opted for biomineralization processes in calcifying animals. Until now, no study has tested for the presence or expression of alpha-CAs in a calcifying marine annelid. The tube building polychaete, Hydroides elegans, is an ideal candidate for studying calcification, because it forms a calcium carbonate tube that adheres tightly to submerged marine surfaces. We have identified ten unique alpha-CA transcripts in transcriptomes from H. elegans, consistent with the eleven total isoforms found in a non-calcifying polychaete, Capitella teleta. Furthermore, we report the successful cloning, expression, and localization of a secreted and a cytosolic CA isoform, HeCA1 and HeCA2 in H. elegans. Transcripts of both genes were localized in the calcifying collar segment of competent larvae and juveniles, suggesting that a combination of externally and internally mediated calcification may be occurring. Finally, we constructed a model for protein evolution that supports extensive gene duplication events that took place within the alpha-CA family.
