Exaptation as a mechanism for functional reinforcement of an animal pheromone system.
We investigated the evolutionary trajectory of a series of 15 kDa proteins – termed persuasins – that were co-opted more recently alongside the ancient sodefrin precursor-like factor (SPF) courtship pheromone system in salamanders. Expression, genomic and molecular phylogenetic analyses show that persuasins originated from a gene that is expressed as a multi-domain protein in internal organs where it has no pheromone function, but underwent gene duplication and neofunctionalisation. The subsequent evolution combined domain-loss and the introduction of a proteolytic cleavage site in the duplicated gene to give rise to two-domain cysteine rich proteins with structural properties similar to SPF pheromones In the absence of an NCBI database for sequences assembled by third party analyses (assembly of publicly available reads, RNA sequencing), we deposited nucleotide and amino acid sequences of persuasin and DUF-persuasin transcripts assembled from publicly available short reads (NCBI: SRA) on the Mendeley Data repository. Sources of publicly available SRA datasets are cited in the main article and supplemental information (Maex et al. (2018) Exaptation as a mechanism for functional reinforcement of an animal pheromone system).