Evolution and Adaptation of Aquaporin Genes in Rodents along a Habitat Moisture Gradient: A Case Study of Eothenomys miletus

To elucidate the adaptive evolution of aquaporin (AQP) genes in arid habitats, this study performed phylogenetic and selection pressure analyses on AQP1 to AQP11 across 15 rodent species, with subsequent experimental validation of candidate genes under positive selection.

In the present study, phylogenetic trees were constructed using MEGA-X and the iTOL online platform, while selection pressure analysis was performed via PAML and the Datamonkey website. Finally, using Eothenomys miletus inhabiting the Hengduan Mountains as the research subject, water stress experiments were conducted by measuring AQP expression levels through ELISA.

Phylogenetic reconstruction using MEGA-X and iTOL indicated that species from humid environments clustered into a distinct clade, implying that moisture availability may have influenced the divergence of AQP genes. Selection analyses implemented in PAML identified one positively selected site each in AQP1, AQP5 and AQP7. Furthermore, signals of positive selection were detected in AQP10 and AQP11 among species from arid habitats. Given the substantial existing literature on AQP1, AQP5 and AQP7 and the limited phenotypic consequences of AQP10 deficiency in mice, this study focused on validating AQP11. After subjecting the endemic species of the Hengduan Mountains, E. miletus, to water deprivation treatment, the protein expression levels of AQP11 were measured using enzyme-linked immunosorbent assay (ELISA). Findings demonstrated significantly elevated AQP11 levels in seven tissues-kidney, brain, liver, heart, small intestine, white adipose tissue (WAT) and brown adipose tissue (BAT)-in the water- deprived group compared to controls. Based on existing evidence, we propose that AQP11 is involved in cellular water stress responses across multiple organs by mediating H₂O₂ transport across the endoplasmic reticulum membrane. Thus, it is hypothesized that the AQP11 gene may play a critical role in the adaptation of rodents to arid environments. This research offers a theoretical basis for further elucidating the mechanisms by which organisms adapt to environmental water stress.