The centromeric protein CENP-C is a base component of the kinetochore. This protein, along with CENP-A has been shown to adaptively evolve in a number of animal and plant species. In order to determine if CENP-C also evolves in fish species, I attempted to retrieve fish CENP-C sequences from GenBank. No Teleostei CENP-C sequences were found either by name or by BLASTP searches with the vertebrate CENP-C motif sequence. A number of putative Teleostei protein sequences were identified in GenBank that have homology to the C-terminal cupin domain of vertebrate CENP-C. These proteins only have partial homology to the CENP-C motif, but evidence is presented that makes it likely that these fish proteins are orthologs of CENP-C. Interestingly, it was also discovered that the CENP-C motif sequence is also mostly present in M18BP1 proteins of fish and some other vertebrates but not in mammals. This finding may have implications for CENP-C and M18BP1 assembly in centromeric regions of different vertebrate taxa.

The centromeric protein CENP-C is a base component of the kinetochore. This protein, along with CENP-A has been shown to adaptively evolve in a number of animal and plant species. In order to determine if CENP-C also evolves in fish species, I attempted to retrieve fish CENP-C sequences from GenBank. No Teleostei CENP-C sequences were found either by name or by BLASTP searches with the vertebrate CENP-C motif sequence. A number of putative Teleostei protein sequences were identified in GenBank that have homology to the C-terminal cupin domain of vertebrate CENP-C. These proteins only have partial homology to the CENP-C motif, but evidence is presented that makes it likely that these fish proteins are orthologs of CENP-C. Interestingly, it was also discovered that the CENP-C motif sequence is also mostly present in M18BP1 proteins of fish and some other vertebrates but not in mammals. This finding may have implications for CENP-C and M18BP1 assembly in centromeric regions of different vertebrate taxa.

Centromeric protein A (CENP-A) is the epigenetic determinant of centromeres. This protein has been shown to be adaptively evolving in a number of animal and plant species. In a previous communication we were able to demonstrate that signs of adaptive evolution were detected in the comparison of CENP-A sequences from three percid fish species. In this study we isolated the CENP-A gene from eight additional species from the Percidae family. With these sequences and those previously obtained, we carried out a more robust statistical analysis of codon specific positive selection in CENP-A coding sequences of eleven percid species. We were able to demonstrate that at least two amino acid positions within the N-terminal tail are under strong positive selection and that one of these positions is potentially a substrate for phosphorylation. While nonsynonymous substitutions were detected in the histone fold domain, these were not statistically supported as resulting from positive selection.

Both centromeric alpha-satellite sequences as well as centromeric protein A (CENP-A) are highly variable in eukaryotes. CENP-A, a histone H3 variant, is thought to act as the epigenetic “mark” for assembly of centromeric proteins. While most of the histone fold domain (HFD) of the CENP-A is fairly well conserved, a portion of this HFD as well as the N-terminal tail show adaptive variation in both plants and animals. Such variation may establish reproductive barriers that may lead to speciation. The family Percidae contains over 200 species most of which are within the subfamily Etheostomatinae. This subfamily represents a species rich radiation of freshwater fishes in North America and these species exhibit both allopatric and sympatric distributions. In order to study the evolution of CENP-A in percid fish species, we have isolated and characterized the CENP-A gene from Etheostoma tallapoosae by PCR based gene walking. As a result of this study we have demonstrated that the Tallapoosa darter CENP-A gene HFD sequences can be isolated from genomic DNA by nested PCR in a manner that does not lead to the amplification of the highly sequence related histone H3 gene. We also demonstrated that PCR based walking can be subsequently used to isolate the rest of the CENP-A gene and adjacent gene sequences. These adjacent gene sequences provide us with a primer binding sites for PCR isolation of the CENP-A gene from other percid species of fishes. An initial comparison of three percid species shows that the N-terminal tail of the percid CENP-A gene shows adaptive evolution.

Background:Mitochondrial DNA of vertebrates contains genes for 13 proteins involved in oxidative phosphorylation. Some of these genes have been shown to undergo adaptive evolution in a variety of species. This study examines all mitochondrial protein coding genes in 11 darter species to determine if any of these genes show evidence of positive selection. Methods:The mitogenome from four darter was sequenced and annotated. Mitogenome sequences for another seven species were obtained from GenBank. Alignments of each of the protein coding genes were subject to codon-based identification of positive selection by Selecton, MEME and FEL. Results:Evidence of positive selection was obtained for six of the genes by at least one of the methods.CYTBwas identified as having evolved under positive selection by all three methods at the same codon location. Conclusions:Given the evidence for positive selection of mitochondrial protein coding genes in darters, a more extensive analysis of mitochondrial gene evolution in all the extant darter species is warranted.

Background: Mitochondrial DNA of vertebrates contains genes for 13 proteins involved in oxidative phosphorylation. Some of these genes have been shown to undergo adaptive evolution in a variety of species. This study examines all mitochondrial protein coding genes in 11 darter species to determine if any of these genes show evidence of positive selection. Methods: The mitogenome from four darter was sequenced and annotated. Mitogenome sequences for another seven species were obtained from GenBank. Alignments of each of the protein coding genes were subject to codon-based identification of positive selection by Selecton, MEME and FEL. Results: Evidence of positive selection was obtained for six of the genes by at least one of the methods. CYTB was identified as having evolved under positive selection by all three methods at the same codon location. Conclusions: Given the evidence for positive selection of mitochondrial protein coding genes in darters, a more extensive analysis of mitochondrial gene evolution in all the extant darter species is warranted.