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A testis‐specific gene within a widely expressed gene: Contrasting evolutionary patterns of two differentially expressed mammalian proteins encoded by a single gene, CAMK 4
Author(s) -
Padhi Abinash,
Ma Li
Publication year - 2015
Publication title -
animal genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 81
eISSN - 1365-2052
pISSN - 0268-9146
DOI - 10.1111/age.12358
Subject(s) - biology , gene , negative selection , genetics , camk , lineage (genetic) , protein kinase a , genome , kinase , autophosphorylation
Summary Understanding the patterns of genetic variations within fertility‐related genes and the evolutionary forces that shape such variations is crucial in predicting the fitness landscapes of subsequent generations. This study reports distinct evolutionary features of two differentially expressed mammalian proteins [Ca MKIV (Ca 2+ /calmodulin‐dependent protein kinase IV ) and CaS (calspermin)] that are encoded by a single gene, CAMK 4 . The multifunctional Ca MKIV , which is expressed in multiple tissues including testis and ovary, is evolving at a relatively low rate (0.46–0.64 × 10 −9 nucleotide substitutions/site/year), whereas the testis‐specific CaS gene, which is predominantly expressed in post‐meiotic cells, evolves at least three to four times faster (1.48–1.98 × 10 −9 substitutions/site/year). Concomitantly, maximum‐likelihood‐based selection analyses revealed that the ubiquitously expressed Ca MKIV is constrained by intense purifying selection and, therefore, remained functionally highly conserved throughout the mammalian evolution, whereas the testis‐specific CaS gene is under strong positive selection. The substitution rates of different mammalian lineages within both genes are positively correlated with GC content, indicating the possible influence of GC ‐biased gene conversion on the estimated substitution rates. The observation of such unusually high GC content of the CaS gene (≈74%), particularly in the lineage that comprises the bovine species, suggests the possible role of GC ‐biased gene conversion in the evolution of CaS that mimics positive selection.