Supplementary materials and methods from Evidence for parallel evolution of a gene involved in the regulation of spermatogenesis

<i>PHD finger protein 7</i> (<i>Phf7</i>) is a male germline specific gene in <i>Drosophila melanogaster</i> that can trigger the male germline sexual fate and regulate spermatogenesis, and its human homologue can rescue fecundity defects in male flies lacking this gene. These findings prompted us to investigate conservation of reproductive strategies through studying the evolutionary origin of this gene. We find that <i>Phf7</i> is present only in select species including mammals and some insects whereas the closely related <i>G2/M-phase specific E3 ubiquitin protein ligase</i> (<i>G2e3</i>) is in the genome of most metazoans. Interestingly, phylogenetic analyses showed that vertebrate and insect <i>Phf7</i> genes did not evolve from a common <i>Phf7</i> ancestor but rather through independent duplication events from an ancestral <i>G2e3</i>. This is an example of parallel evolution in which a male germline factor evolved at least twice from a pre-existing template to develop new regulatory mechanisms of spermatogenesis.