No abstract

The CYP8B1 gene is known to catalyse reactions that determine the ratio of primary bile salts 2 and the loss of this gene has recently been linked to lack of cholic acid in the bile of naked-2 mole rats, elephants and manatees using forward genomics approaches. We screened the 2 CYP8B1 gene sequence of more than 200 species and test for relaxation of selection along 3 each terminal branch. The need for retaining a functional copy of the CYP8B1 gene is 3 established by the presence of a conserved open reading frame across most species screened 3 in this study. Interestingly, the dietary switch from bovid to cetacean species is accompanied 3 by an exceptional ten amino-acid extension at the C-terminal end through a single base 3 frame-shift deletion. We also verify that the coding frame disrupting mutations previously 3 reported in the elephant are correct, are shared by extinct Elephantimorpha species and 3 coincide with the dietary switch to herbivory. Relaxation of selection in the CYP8B1 gene of 3 the wombat (Vombatus ursinus) also corresponds to drastic change in diet. In summary, our 3 forward genomics based screen of bird and mammal species identifies recurrent changes in 3 the selection landscape of the CYP8B1 gene concomitant with a change in dietary lipid 4 content.

3 1 established by the presence of a conserved open reading frame across most species screened 3 2 in this study. Interestingly, the dietary switch from bovid to cetacean species is accompanied 3 3by an exceptional ten amino-acid extension at the C-terminal end through a single base 3 4 frame-shift deletion. We also verify that the coding frame disrupting mutations previously 3 5 reported in the elephant are correct, are shared by extinct Elephantimorpha species and 3 6 coincide with the dietary switch to herbivory. Relaxation of selection in the CYP8B1 gene of 3 7 the wombat (Vombatus ursinus) also corresponds to drastic change in diet. In summary, our 3 8 forward genomics based screen of bird and mammal species identifies recurrent changes in 3 9 the selection landscape of the CYP8B1 gene concomitant with a change in dietary lipid 4 0 content. 4 1

Functional diversification, a higher evolutionary rate, and intense positive selection help a limited number of immune genes interact with many continuously evolving pathogens. Repeats in protein-coding regions are a well-known source of rapid functional diversification, adaptive variation, and evolutionary novelty. Repeats play a crucial role in biochemical functions like functional diversification of transcription regulation, protein kinases, cell adhesion, signaling pathways, morphogenesis, DNA repair, recombination, and RNA processing. Repeat length variation can change the associated protein's interaction, efficacy, and overall protein network. Repeats have an intrinsic unstable nature and can potentially evolve rapidly and expedite the acquisition of complex phenotypic traits and functions. Because of their ability to generate rapid, adaptive variations over short evolutionary distances, repeats are considered "tuning knobs." Repeat length variation in specific genes, like RUNX2 and ALX4, is associated with morphological and physiological changes across vertebrates. Here we study repeat length variation as a potent source of species-specific immune diversification across several clades of tetrapods. Moreover, we provide a clade-wise comprehensive list of immune genes with repeat types for future studies of morphological/evolutionary changes within species groups. We observe significant repeat length variation of FASLG in Rodentia and C1QC in Primates' contrasting species groups.