Multiple Independent Recruitment of Sodefrin Precursor-like Factors in Anuran Sexually Dimorphic Glands.

Chemical signaling in animals often plays a central role in eliciting a variety of responses during reproductive interactions between males and females. One of the best known vertebrate courtship pheromone systems is that of Sodefrin Precursor-like Factors (SPFs), a family of two-domain three-finger proteins with a female-receptivity enhancing function, currently known only from salamanders. We combined whole transcriptome sequencing, proteomics, histology and molecular phylogenetics in a comparative approach to investigate SPF use during courtship across the evolutionary tree of anurans (frogs and toads).Since male frogs use different courtship or amplexus (i.e. the embrace of the female by the male) strategies to deliver the secretion of these glands to the female (Table 1), we investigated gene expression (RNA sequencing) in a wide variety of tissues (sexually dimorphic breeding glands and microgland-containing skins from different male body parts, such as chin, fingers and thumbs, armpits, thighs, and trunk) to search for a potential wider utilization of SPFs in sexual chemical signaling.