title: A horizontal gene transfer supported the evolution of an early metazoan biomineralization strategy.
abstract: BACKGROUND
  The synchronous and widespread adoption of the ability to biomineralize was a defining event for metazoan evolution during the late Precambrian/early Cambrian 545 million years ago. However our understanding on the molecular level of how animals first evolved this capacity is poor. Because sponges are the earliest branching phylum of biomineralizing metazoans, we have been studying how biocalcification occurs in the coralline demosponge Astrosclera willeyana.
  
  
  RESULTS
  We have isolated and characterized a novel protein directly from the calcified spherulites of A. willeyana. Using three independent lines of evidence (genomic architecture of the gene in A. willeyana, spatial expression of the gene product in A. willeyana and genomic architecture of the gene in the related demosponge Amphimedon queenslandica), we show that the gene that encodes this protein was horizontally acquired from a bacterium, and is now highly and exclusively expressed in spherulite forming cells.
  
  
  CONCLUSIONS
  Our findings highlight the ancient and close association that exists between sponges and bacteria, and provide support for the notion that horizontal gene transfer may have been an important mechanism that supported the evolution of this early metazoan biomineralisation strategy.
authors.affiliation: Courant Research Centre Geobiology, Georg-August-University of Göttingen, Goldschmidtstrasse 3, Göttingen, Germany. djackso@uni-goettingen.de
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Jackson
authors.forename: Luciana
authors.initials: L
authors.lastname: Macis
authors.forename: Joachim
authors.initials: J
authors.lastname: Reitner
authors.forename: Gert
authors.initials: G
authors.lastname: Wörheide
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D005075:Biological Evolution; D002113:Calcification, Physiologic; D022761:Gene Transfer, Horizontal; D008903:Minerals / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011161:Porifera / Q000235:genetics / Q000502:physiology*; D011506:Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D008903:Minerals; D011506:Proteins