Analyses of Corallimorpharian Transcriptomes Provide New Perspectives on the Evolution of Calcification in the Scleractinia (Corals).
Corallimorpharians (coral-like anemones) have a close phylogenetic relationship with scleractinians (hard corals) and can potentially provide novel perspectives on the evolution of biomineralization within the anthozoan subclass Hexacorallia. A survey of the transcriptomes of three representative corallimorpharians led to the identification of homologs of some skeletal organic matrix proteins (SOMPs) previously considered to be restricted to corals.Carbonic anhydrases (CAs), which are ubiquitous proteins involved in CO2 trafficking, are involved in both coral calcification and photosynthesis by endosymbiotic Symbiodinium (zooxanthellae). These multiple roles are assumed to place increased demands on the CA repertoire and have presumably driven the elaboration of the complex CA repertoires typical of corals (note that "corals" are defined here as reef-building Scleractinia). Comparison of the CA inventories of corallimorpharians with those of corals reveals that corals have specifically expanded the secreted and membrane-associated type CAs, whereas similar complexity is observed in the two groups with respect to other CA types.Comparison of the CA complement of the nonsymbiotic corallimorph Corynactis australis with that of Ricordea yuma, a corallimorph which normally hosts Symbiodinium, reveals similar numbers and distribution of CA types and suggests that an expansion of the CA repertoire has been necessary to enable calcification but may not be a requirement to enable symbiosis. Consistent with this idea, preliminary analysis suggests that the CA complexity of zooxanthellate and nonzooxanthellate sea anemones is similar.The comparisons above suggest that although there are relatively few new genes in the skeletal organic matrix of corals (which controls the skeleton deposition process), the evolution of calcification required an expanded repertoire of secreted and membrane-associated CAs.
Comparative Genomics Centre, Department of Molecular and Cell Biology, James Cook University, Townsville, Queensland, Australia.|ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.
Mei-Fang
MF
Lin
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.
Aurelie
A
Moya
Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
Hua
H
Ying
Biodiversity Research Centre, Academia Sinica, Nangang, Taipei, Taiwan.|Taiwan International Graduate Program (TIGP)-Biodiversity, Academia Sinica, Nangang, Taipei, Taiwan.
Chaolun Allen
CA
Chen
Comparative Genomics Centre, Department of Molecular and Cell Biology, James Cook University, Townsville, Queensland, Australia.
Ira
I
Cooke
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.|Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
Eldon E
EE
Ball
ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.|Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
Sylvain
S
Forêt
Comparative Genomics Centre, Department of Molecular and Cell Biology, James Cook University, Townsville, Queensland, Australia.|ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, Australia.
David J
DJ
Miller
D000818:Animals; D037421:Anthozoa / Q000235:genetics*; D005075:Biological Evolution; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism*; D010802:Phylogeny; D017422:Sequence Analysis, DNA / Q000379:methods*; D059467:Transcriptome
D002118:Calcium
carbonic anhydrase; coral calcification; corallimorpharian; molecular evolution; skeletal organic matrix proteins