Differential Expression in Testis and Liver Transcriptomes from Four Species of Peromyscus (Rodentia: Cricetidae)

The genus Peromyscus represents a rapidly diverged clade of Cricetid rodents that contains multiple cryptic species and has a propensity for morphologic conservation across its members. The unresolved relationships in previously proposed phylogenies reflect a suspected rapid adaptive radiation. To identify functional groups of genes that may be important in reproductive isolation in a reoccurring fashion across the Peromyscus phylogeny, liver and testis transcriptomes from four species (P. attwateri, P. boylii, P. leucopus, and P. maniculatus) were generated and differential expression (DE) tests were conducted. Taxa were selected to represent members diverged from a common ancestor: P. attwateri + P. boylii (common ancestor A), and P. leucopus + P. maniculatus (common ancestor B). Comparison of clades (A vs B) suggested 346 transcripts had significant DE in the liver dataset whereas significant DE was identified for 929 transcripts in the testis dataset. Further, 66 genes had DE isoforms in the 929 testis transcripts and most of these functioned in major reproductive roles such as acrosome assembly, binding to the zona pellucida, and spermatogenesis. DE transcripts in the testis mapped to specific GO terms (binding of sperm to zona pellucida, sperm-egg recognition, and cell-cell recognition), whereas DE transcripts in the liver mapped to more broad GO terms (metabolic processes, response to chemical, and triglyceride mobilization). These results suggest that a suite of genes that conduct similar functions in the testes may be responsible for the adaptive radiation events and potential reoccurring speciation of Peromyscus in terms of reproduction through varying expression levels.