# New Insights Into the Evolution of Immune Adaptors in Murid Rodents

## TL;DR

This study explores how immune adaptors evolved in murid rodents, finding evidence of purifying selection and adaptive changes in specific genes.

## Contribution

The study provides new insights into the molecular evolution of immune adaptors in murid rodents across multiple timescales.

## Key findings

- Immune adaptors in murid rodents are mostly under purifying selection, with some positively selected sites in MAL and MyD88.
- Genetic diversity in adaptor genes is reduced in Rattus tanezumi and Rattus norvegicus compared to noncoding regions.
- Identical or nearly identical allelic variants were found between Rattus tanezumi and Rattus norvegicus in adaptor genes.

## Abstract

The evolutionary dynamics of immune adaptors in wildlife remain poorly understood, despite their critical role in host–pathogen interactions. In this study, we investigated the molecular evolution of five TIR domain‐containing adaptors (MAL, MyD88, SARM, TRAM, and TRIF) in murid rodents across both interspecific and population levels to provide an integrative view of their evolutionary trajectories. Our analyses demonstrate that these adaptors are predominantly under purifying selection in murids, yet contain specific positively selected sites in MAL and MyD88, indicating localized adaptive fine‐tuning. These positively selected amino acid sites exhibited substantial genetic divergence among murid species. Within populations, we observed reduced genetic diversity in the adaptor genes compared with noncoding regions across the whole genome in both
Rattus tanezumi
and
Rattus norvegicus
, and no significant signals of recent positive or negative selection were detected in either species. Notably, we identified identical or nearly identical allelic variants between these two rat species across all five adaptor genes. Collectively, this study delineates the evolution of immune adaptors in murids across both deep and recent timescales, advancing our understanding of adaptive evolution in multilevel immune systems.

TIR domain‐containing adaptors were evolved under purifying selection in murine. Positively selected sites were identified in Mal and Myd88 genes. Reduced genetic diversity of each adaptor gene was observed in two rat populations. Shared polymorphisms were common phenomena in rat adaptors.