An association between differential expression and genetic divergence in the Patagonian olive mouse (Abrothrix olivacea)

Abstract

Recent molecular studies have found striking differences between desert-adapted species and model mammals regarding water conservation. In particular, aquaporin 4, a classical gene involved in water regulation of model species, is absent or not expressed in the kidneys of desert-adapted species. To further understand the molecular response to water availability, we studied the Patagonian olive mouse Abrothrix olivacea, a species with an unusually broad ecological tolerance that exhibits a great urine concentration capability. The species is able to occupy both the arid Patagonian steppe and the Valdivian and Magellanic forests. We sampled 95 olive mouse specimens from four localities (two in the steppe and two in the forests) and analysed both phenotypic variables and transcriptomic data to investigate the response of this species to the contrasting environmental conditions. The relative size of the kidney and the ratio of urine to plasma concentrations were, as expected, negatively correlated with annual rainfall. Expression analyses uncovered nearly 3,000 genes that were differentially expressed between steppe and forest samples and indicated that this species resorts to the "classical" gene pathways for water regulation. Differential expression across biomes also involves genes that involved in immune and detoxification functions. Overall, genes that were differentially expressed showed a slight tendency to be more divergent and to display an excess of intermediate allele frequencies, relative to the remaining loci. Our results indicate that both differential expression in pathways involved in water conservation and geographical allelic variation are important in the occupation of contrasting habitats by the Patagonian olive mouse.

Environment predicts repeated body size shifts in a recent radiation of Australian mammals*

“…Specifically among rodents, kidney function (MacMillen and Lee ; Giorello et al. ), diet (Degen et al. ), burrowing (Walsberg ), and sociality (Ebensperger ) are likely often associated with environment, particularly as adaptations to arid environments.…”

“…This variation in body mass may be the result of selection toward different fitness optima in disparate biomes, for example, through conferring advantages in thermoregulation or water conservation (Gür and Kart Gür ; Giorello et al. ). Using occurrence data, body mass as a measure of body size, and Bayesian phylogenetic multilevel modeling, we test whether body size in the Pseudomys Division can be predicted by their biome association and by continuous environmental variables.…”

Comparative and population genomics approaches reveal the basis of adaptation to deserts in a small rodent

“…To identify genes associated with desert adaptation and to investigate the factors affecting adaptation using the cactus mouse as a model, we first generated a chromosome-level genome assembly and then integrated comparative, population, and functional genomics approaches. As dehydration is a primary challenge desert animals face, we expected to identify signatures of selection associated with metabolism and sodium-water balance (i.e.adaptations that either enhance production of metabolic water or prevent fluid loss via excretion) in line with previous studies in the cactus mouse and other desert-adapted species (Bactrian Camels Genome Sequencing and Analysis Consortium et al, 2012;Giorello et al, 2018;Marra et al, 2014;Takei et al, 2012;Wu et al, 2014;Yang et al, 2016) . Our analyses of gene family evolution and selective sweeps point instead to regulation of protein synthesis and degradation as the main target of selection.…”

“…This pathway regulates water retention and reabsorption in the kidney, primarily through changes in reno-vascular tone. Aquaporins, transmembrane water channel proteins, are also involved in water reabsorption and urine concentration, and changes in their expression levels have been associated with dry environments in kangaroo rats (Marra et al, 2014(Marra et al, , 2012 and the Patagonian olive mouse (Giorello et al, 2018) .…”

Contrasting patterns of divergence at the regulatory and sequence level in European Daphnia galeata natural populations

“…Correlating expression profiles with sequence divergence helps to identify transcripts that are potentially under the influence of local adaptation at both gene expression and sequence level. Linking gene expression profiles with sequence polymorphisms and their associated functions aids in understanding the genetic basis of adaptation as seen in the desert‐adapted mouse ( Peromyscus eremicus ; MacManes & Eisen, ) and in the Patagonian olive mouse ( Abrothrix olivacea ; Giorello et al, ). Our results revealed ~30% of the transcripts to share divergence at both sequence and regulatory level (Figure ).…”