Kordonowy, L. | bioRxiv Science

bioRxiv2018

Transcriptomic analyses reveal tissue-specific selection on genes related to apoptotic processes in the subterranean rodent, Ctenomys sociabilis

Specialization for a subterranean existence is expected to impact multiple aspects of an organisms biology, including behavior, physiology, and genomic structure. While the phenotypic correlates of life underground have been extensively characterized, the genetic bases for these traits are not well understood, due in part to the challenges of generating large, multi-locus data sets using traditional DNA sequencing strategies. To begin exploring the genomic architecture of adaptation to a subterranean existence, we generated high-quality de novo transcriptome assemblies for 8 different tissue types (hippocampus, hypothalamus, kidney, liver, spleen, ovary, testis, skin) obtained from the colonial tuco-tuco (Ctenomys sociabilis), a group-living species of subterranean rodent that is endemic to southwestern Argentina. From these transcriptomes, we identified genes that are evolving more rapidly in the C. sociabilis lineage compared to other subterranean species of rodents. These comparisons suggest that genes associated with immune response, cell-cycle regulation, and heavy metal detoxification have been subject to positive selection in C. sociabilis. Comparisons of transcripts from different tissues suggest that the spleen and liver - organs involved in immune function and detoxification - may be particularly important sites for these adaptations, thereby underscoring the importance of including multiple tissue types in analyses of transcriptomic variation. In addition to providing an important resource for future genomic studies of C. sociabilis, our analyses generate new insights into the genomic architecture of functionally significant phenotypic traits in free-living mammals.

genomics↗

bioRxiv2016

Transcriptomic Evidence for Reproductive Suppression in Male Peromyscus eremicus (Cactus Mouse) Subjected to Acute Dehydration

The understanding of genomic and physiological mechanisms related to how organisms living in extreme environments survive and reproduce is an outstanding question facing evolutionary and organismal biologists. One interesting example of adaptation is related to the survival of mammals in deserts, where extreme water limitation is common. Research on desert rodent adaptations has focused predominantly on adaptations related to surviving dehydration, while potential reproductive physiology adaptations for acute and chronic dehydration have been relatively neglected. This study aims to explore the reproductive consequences of acute dehydration by utilizing RNAseq data in the desert-specialized cactus mouse (Peromyscus eremicus). Specifically, we exposed 22 male cactus mice to either acute dehydration or control (fully hydrated) treatment conditions, quasimapped testes-derived reads to a cactus mouse testes transcriptome, and then evaluated patterns of differential transcript and gene expression. Following statistical evaluation with multiple analytical pipelines, nine genes were consistently differentially expressed between the hydrated and dehydrated mice. We hypothesized that male cactus mice would exhibit minimal reproductive responses to dehydration; therefore, this low number of differentially expressed genes between treatments aligns with current perceptions of this species extreme desert specialization. However, these differentially expressed genes include Insulin-like 3 (Insl3), a regulator of male fertility and testes descent, as well as the solute carriers Slc45a3 and Slc38a5, which are membrane transport proteins that may facilitate osmoregulation. Together, these results suggest that in male cactus mice, acute dehydration may be linked to reproductive modulation via Insl3, but not through gene expression differences in the subset of other a priori tested reproductive hormones. Although water availability is a reproductive cue in desert-rodents exposed to chronic drought, potential reproductive modification via Insl3 in response to acute water-limitation is a result which is unexpected in an animal capable of surviving and successfully reproducing year-round without available external water sources. Indeed, this work highlights the critical need for integrative research that examines every facet of organismal adaptation, particularly in light of global climate change, which is predicted, amongst other things, to increase climate variability, thereby exposing desert animals more frequently to the acute drought conditions explored here.

evolutionary biology↗