title: Origin and diversification of a salamander sex pheromone system.
abstract: Sex pheromones form an important facet of reproductive strategies in many organisms throughout the Animal Kingdom. One of the oldest known sex pheromones in vertebrates are proteins of the Sodefrin Precursor-like Factor (SPF) system, which already had a courtship function in early salamanders. The subsequent evolution of salamanders is characterized by a diversification in courtship and reproduction, but little is known on how the SPF pheromone system diversified in relation to changing courtship strategies. Here, we combined transcriptomic, genomic, and phylogenetic analyses to investigate the evolution of the SPF pheromone system in nine salamandrid species with distinct courtship displays. First, we show that SPF originated from vertebrate three-finger proteins and diversified through multiple gene duplications in salamanders, while remaining a single copy in frogs. Next, we demonstrate that tail-fanning newts have retained a high phylogenetic diversity of SPFs, whereas loss of tail-fanning has been associated with a reduced importance or loss of SPF expression in the cloacal region. Finally, we show that the attractant decapeptide sodefrin is cleaved from larger SPF precursors that originated by a 62 bp insertion and consequent frameshift in an ancestral Cynops lineage. This led to the birth of a new decapeptide that rapidly evolved a pheromone function independently from uncleaved proteins.
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Sunita
authors.initials: S
authors.lastname: Janssenswillen
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Vandebergh
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Dag
authors.initials: D
authors.lastname: Treer
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Bert
authors.initials: B
authors.lastname: Willaert
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Margo
authors.initials: M
authors.lastname: Maex
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
authors.forename: Ines
authors.initials: I
authors.lastname: Van Bocxlaer
authors.affiliation: Amphibian Evolution Lab, Biology Department, Vrije Universiteit Brussel (VUB), Brussels, Belgium fbossuyt@vub.ac.be.
authors.forename: Franky
authors.initials: F
authors.lastname: Bossuyt
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D012724:Sex Attractants / Q000145:classification / Q000235:genetics*; D014562:Caudata / Q000235:genetics* / Q000378:metabolism*
chemical_list: D012724:Sex Attractants
keywords: SPF pheromone system; amphibians; evolution