title: A comparative view of early development in the corals Favia lizardensis, Ctenactis echinata, and Acropora millepora - morphology, transcriptome, and developmental gene expression.
abstract: BACKGROUND
  Research into various aspects of coral biology has greatly increased in recent years due to anthropogenic threats to coral health including pollution, ocean warming and acidification. However, knowledge of coral early development has lagged. The present paper describes the embryonic development of two previously uncharacterized robust corals, Favia lizardensis (a massive brain coral) and Ctenactis echinata (a solitary coral) and compares it to that of the previously characterized complex coral, Acropora millepora, both morphologically and in terms of the expression of a set of key developmental genes.
  
  
  RESULTS
  Illumina sequencing of mixed age embryos was carried out, resulting in embryonic transcriptomes consisting of 40605 contigs for C.echinata (N50 = 1080 bp) and 48536 contigs for F.lizardensis (N50 = 1496 bp). The transcriptomes have been annotated against Swiss-Prot and were sufficiently complete to enable the identification of orthologs of many key genes controlling development in bilaterians. Developmental series of images of whole mounts and sections reveal that the early stages of both species contain a blastocoel, consistent with their membership of the robust clade. In situ hybridization was used to examine the expression of the developmentally important genes brachyury, chordin and forkhead. The expression of brachyury and forkhead was consistent with that previously reported for Acropora and allowed us to confirm that the pseudo-blastopore sometimes seen in robust corals such as Favia spp. is not directly associated with gastrulation. C.echinata chordin expression, however, differed from that seen in the other two corals.
  
  
  CONCLUSIONS
  Embryonic transcriptomes were assembled for the brain coral Favia lizardensis and the solitary coral Ctenactis echinata. Both species have a blastocoel in their early developmental stages, consistent with their phylogenetic position as members of the robust clade. Expression of the key developmental genes brachyury, chordin and forkhead was investigated, allowing comparison to that of their orthologs in Acropora, Nematostella and bilaterians and demonstrating that even within the Anthozoa there are significant differences in expression patterns.
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT, 0200, Australia. nokubo@tku.ac.jp.|Current Address: Department of Economics, Tokyo Keizai University, 1-7-34 Minamimachi, Kokubunji, Tokyo, Japan. nokubo@tku.ac.jp.
authors.forename: Nami
authors.initials: N
authors.lastname: Okubo
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT, 0200, Australia. david.hayward@anu.edu.au.
authors.forename: David C
authors.initials: DC
authors.lastname: Hayward
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT, 0200, Australia. sylvain.foret@anu.edu.au.|ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811, Australia. sylvain.foret@anu.edu.au.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Forêt
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT, 0200, Australia. eldon.ball@anu.edu.au.|ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811, Australia. eldon.ball@anu.edu.au.
authors.forename: Eldon E
authors.initials: EE
authors.lastname: Ball
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D005326:Fetal Proteins / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D050437:Genes, Developmental; D006023:Glycoproteins / Q000378:metabolism; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D010802:Phylogeny; D020825:T-Box Domain Proteins / Q000378:metabolism; D059467:Transcriptome; D000098908:Brachyury Protein
chemical_list: D005326:Fetal Proteins; D051858:Forkhead Transcription Factors; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein; C054234:chordin