title: The molecular evolution of spiggin nesting glue in sticklebacks.
abstract: Gene duplication and subsequent divergence can lead to the evolution of new functions and lineage-specific traits. In sticklebacks, the successive duplication of a mucin gene (MUC19) into a tandemly arrayed, multigene family has enabled the production of copious amounts of 'spiggin', a secreted adhesive protein essential for nest construction. Here, we examine divergence between spiggin genes among three-spined sticklebacks (Gasterosteus aculeatus) from ancestral marine and derived freshwater populations, and propose underpinning gene duplication mechanisms. Sanger sequencing revealed substantial diversity among spiggin transcripts, including alternatively spliced variants and interchromosomal spiggin chimeric genes. Comparative analysis of the sequenced transcripts and all other spiggin genes in the public domain support the presence of three main spiggin lineages (spiggin A, spiggin B and spiggin C) with further subdivisions within spiggin B (B1, B2) and spiggin C (C1, C2). Spiggin A had diverged least from the ancestral MUC19, while the spiggin C duplicates had diversified most substantially. In silico translations of the spiggin gene open reading frames predicted that spiggins A and B are secreted as long mucin-like polymers, while spiggins C1 and C2 are secreted as short monomers, with putative antimicrobial properties. We propose that diversification of duplicated spiggin genes has facilitated local adaptation of spiggin to a range of aquatic habitats.
authors.affiliation: Department of Neuroscience, Psychology and Behaviour, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK.
authors.forename: P J
authors.identifier: http://orcid.org/0000-0003-4303-5943
authors.initials: PJ
authors.lastname: Seear
authors.affiliation: Department of Genetics, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK.
authors.forename: E
authors.initials: E
authors.lastname: Rosato
authors.affiliation: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK.
authors.forename: W P
authors.initials: WP
authors.lastname: Goodall-Copestake
authors.affiliation: Department of Neuroscience, Psychology and Behaviour, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, LE1 7RH, UK.
authors.forename: I
authors.initials: I
authors.lastname: Barber
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics*; D020440:Gene Duplication; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D016366:Open Reading Frames; D017422:Sequence Analysis, DNA; D023701:Smegmamorpha / Q000235:genetics*
chemical_list: D029941:Fish Proteins; C429543:spiggin
keywords: Gasterosteus aculeatus; adaptation; gene duplication; gene family; nest building; retrotransposon