Evolution of biomineralization proteins in Cnidaria

Recently, the effects of ocean acidification on coral calcification have received significant interest. However, similar information is lacking for soft corals, which produce internal calcite sclerites. This poor understanding of the calcifying mechanisms makes it difficult to predict the response of soft corals to increased ocean acidification. In order to better understand the potential effects of increased atmospheric CO₂, it is crucial that we expand and enhance our knowledge of soft coral calcification biomolecules. Toward this end, we use molecular biology techniques to understand the evolutionary history of a Cnidarian highly acidic protein, previously thought to be limited to stony corals. Coral acid rich protein (CARP) 4, is a coralspecific protein exhibiting a high proportion (>20%) of the acidic amino acids (aspartic and glutamic acids). Previously thought to be stony coral-specific, the partial sequence of a soft coral sclerite protein appears similar to CARP4. An alignment of homologues of four stony corals and CARP4 proteins with an N-terminal peptide from Lobophytum crassum sclerites suggests that soft corals possess a member of the CARP4 subfamily. Through a series of molecular biology techniques, the presence of CARP4 in soft corals can be verified. If L. crassum does indeed possess the CARP4 gene, phylogenetic comparison of soft versus stony coral CARP4 will be performed to trace the evolutionary track of this Cnidarian-specific biomineralization protein.