Conserved Signatures in Protein Sequences Reliably Demarcate Different Clades of Rodents/Glires Species and Consolidate Their Evolutionary Relationships.

The grandorder Glires, consisting of the orders Rodentia and Lagomorpha, encompasses a significant portion of the extant mammalian species including Rat, Mouse, Squirrel, Guinea pig and Beaver. Glires species play an important role in the ecosystem and provide valuable animal models for genetic studies and animal testing. Thus, it is important to reliably determine their evolutionary relationships and identify molecular characteristics that are specific for different species groups within the Glires. In this work, we have constructed a phylogenetic tree for >30 genome sequenced Glires species based on concatenated sequences of 25 conserved proteins. In this tree, members of different orders, suborders, and families within Glires formed strongly supported clades, and their interrelationships were also generally reliably resolved. In parallel, we conducted comparative analyses on more than 1500 protein sequences from Glires species to identify highly conserved molecular markers. These markers were comprised of conserved signature indels (CSIs) in proteins, which are specific for different Rodentia/Glires clades. Of the 41 novel CSIs identified in this work, some are specific for the entire Glires, Rodentia, or Lagomorpha clades, whereas many others reliably demarcate different family/suborder level clades of Rodentia (viz. Myomorpha, Castorimorpha, Sciuromorpha, Hystricomorpha, and Muroidea). Additionally, some of the CSIs also provide information regarding the interrelationships among Rodentia subgroups. Our analysis has also identified one CSI that is commonly shared by the Glires and Scandentia species (tree shrew), however, its evolutionary significance is unclear. Several of the identifed rodents-specific CSIs are present in conserved disease-related proteins. Thus, they provide novel molecular markers for genetic and biochemical studies on the functions of these proteins.