title: Analysis of evolutionarily conserved innate immune components in coral links immunity and symbiosis.
abstract: Reef-building corals are representatives of one of the earliest diverging metazoan lineages and are experiencing increases in bleaching events (breakdown of the coral-Symbiodinium symbiosis) and disease outbreaks. The present study investigates the roles of two pattern recognition proteins, the mannose binding lectin Millectin and a complement factor C3-like protein (C3-Am), in the coral Acropora millepora. The results indicate that the innate immune functions of these molecules are conserved and arose early in evolution. C3-Am is expressed in response to injury, and may function as an opsonin. In contrast, Millectin expression is up-regulated in response to lipopolysaccharide and peptidoglycan. These observations, coupled with localization of Millectin in nematocysts in epidermal tissue, and reported binding of pathogens, are consistent with a key role for the lectin in innate immunity. Furthermore, Millectin was consistently detected binding to the symbiont Symbiodinium in vivo, indicating that the Millectin function of recognition and binding of non-self-entities may have been co-opted from an ancient innate immune system into a role in symbiosis.
authors.affiliation: Centre for Marine Studies, The University of Queensland, St. Lucia, QLD 4072, Australia. c.kvennefors@uq.edu.au
authors.forename: E Charlotte E
authors.initials: EC
authors.lastname: Kvennefors
authors.forename: William
authors.initials: W
authors.lastname: Leggat
authors.forename: Caroline C
authors.initials: CC
authors.lastname: Kerr
authors.forename: Tracy D
authors.initials: TD
authors.lastname: Ainsworth
authors.forename: Ove
authors.initials: O
authors.lastname: Hoegh-Guldberg
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Barnes
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D037421:Anthozoa; D003001:Cloning, Molecular; D003176:Complement C3 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017124:Conserved Sequence / Q000235:genetics; D019143:Evolution, Molecular; D007113:Immunity, Innate / Q000235:genetics; D007114:Immunization; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism; D037601:Mannose-Binding Lectin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D058894:Nematocyst / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D009895:Opsonin Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010587:Phagocytosis / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D051192:Receptors, Pattern Recognition / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics / Q000276:immunology; D015854:Up-Regulation; D014947:Wounds and Injuries / Q000276:immunology
chemical_list: D003176:Complement C3; D008070:Lipopolysaccharides; D037601:Mannose-Binding Lectin; D009895:Opsonin Proteins; D051192:Receptors, Pattern Recognition