title: The organizer in evolution-gastrulation and organizer gene expression highlight the importance of Brachyury during development of the coral, Acropora millepora.
abstract: Organizer activity, once thought to be restricted to vertebrates, has ancient origins. However, among non-bilaterians, it has only been subjected to detailed investigation during embryonic development of the sea anemone, Nematostella vectensis. As a step toward establishing the extent to which findings in Nematostella can be generalized across the large and diverse phylum Cnidaria, we examined the expression of some key organizer and gastrulation genes during the embryonic development of the coral Acropora millepora. Although anemones and corals both belong to the cnidarian class Anthozoa, the two lineages diverged during the Cambrian and the morphological development of Acropora differs in several important respects from that of Nematostella. While the expression patterns of the key genes brachyury, bmp2/4, chordin, goosecoid and forkhead are broadly similar, developmental differences between the two species enable novel observations, and new interpretations of their significance. Specifically, brachyury expression during the flattened prawnchip stage before gastrulation, a developmental peculiarity of Acropora, leads us to suggest that it is the key gene demarcating ectoderm from endoderm in Acropora, and by implication in other cnidarians, whereas previous studies in Nematostella proposed that forkhead plays this role. Other novel observations include the transient expression of Acropora forkhead in scattered ectodermal cells shortly after gastrulation, and in the developing mesenterial filaments, with no corresponding expression reported in Nematostella. In addition, the expression patterns of goosecoid and bmp2/4 confirm the fundamental bilaterality of the Anthozoa.
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia.
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.
authors.forename: Lauretta C
authors.initials: LC
authors.lastname: Grasso
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia; School of Molecular Biosciences, The University of Adelaide, Adelaide, SA 5005, Australia.
authors.forename: Robert
authors.initials: R
authors.lastname: Saint
authors.affiliation: ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia; School of Pharmacy and Molecular Sciences, James Cook University, Townsville, QLD 4811, Australia.
authors.forename: David J
authors.initials: DJ
authors.lastname: Miller
authors.affiliation: Evolution, Ecology and Genetics, Bldg 46, Research School of Biology, Australian National University, Canberra, ACT 0200, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia. Electronic address: eldon.ball@anu.edu.au.
authors.forename: Eldon E
authors.initials: EE
authors.lastname: Ball
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000196:embryology* / Q000378:metabolism; D005075:Biological Evolution; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004475:Ectoderm / Q000196:embryology / Q000378:metabolism; D004707:Endoderm / Q000196:embryology / Q000378:metabolism; D005326:Fetal Proteins / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D051956:Goosecoid Protein / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D020897:Organizers, Embryonic / Q000378:metabolism*; D013045:Species Specificity; D020825:T-Box Domain Proteins / Q000378:metabolism*; D000098908:Brachyury Protein
chemical_list: D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D017931:DNA Primers; D018076:DNA, Complementary; D005326:Fetal Proteins; D051858:Forkhead Transcription Factors; D051956:Goosecoid Protein; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein
keywords: Acropora; Brachyury; Coral; Gastrulation; Nematostella; Organizer