Evolution of the Male-Determining Gene SRY Within the Cat Family Felidae

摘要

In most placental mammals, SRY is a single-copy gene located on the Y chromosome and is the triggernfor male sex determination during embryonic development. Here, we present comparative genomicnanalyses of SRY (705 bp) along with the adjacent noncoding 59 flank (997 bp) and 39 flank (948 bp) in 36nspecies of the cat family Felidae. Phylogenetic analyses indicate that the noncoding genomic flanks andnSRY closely track species divergence. However, several inconsistencies are observed in SRY. Overall, thengene exhibits purifying selection to maintain function (v ?0.815) yet SRY is under positive selection inntwo of the eight felid lineages. SRY has low numbers of nucleotide substitutions, yet most encode aminonacid changes between species, and four different species have significantly altered SRY due to insertiondeletions. Moreover, fixation of nonsynonymous substitutions between sister taxa is not consistent andnmay occur rapidly, as in the case of domestic cat, or not at all over long periods of time, as observed withinnthe Panthera lineage. The former resembles positive selection during speciation, and the latter purifyingnselection to maintain function. Thus, SRY evolution in cats likely reflects the different phylogeographicnhistories, selection pressures, and patterns of speciation in modern felids.