The tribal radiation of the family Bovidae (Artiodactyla) and the evolution of the mitochondrial cytochrome b gene

The nucleotide sequence of the complete mitochondrial cytochrome b gene has been determined and compared for 51 species of the family Bovidae and 10 potential pecoran and tragulid outgroups. A detailed saturation analysis at each codon position relative to the maximum parsimony procedure indicates that all transitions on third codon positions do not accumulate in a similar fashion: C-T are more saturated than A-G substitutions. The same trend is observed for second positions but not for first positions where A-G and C-T transitions exhibit roughly the same levels of saturation. Maximum parsimony reconstructions were weighted according to these observations. Maximum parsimony, maximum likelihood, and distance phylogenetic reconstructions all depict a major split within Bovidae. The subfamily Bovinae includes four multifurcating tribes and subtribes: Boselaphini, Tragelaphini, cattle-Bovini (Bos and Bison), and buffalo-Bovini (Bubalus and Syncerus). Its sister group is the subfamily Antilopinae, i.e., all non-Bovinae taxa, represented by seven lineages: Antilopini (including Saiga), Caprini sensu lato (i. e., Caprinae including Pantholops), Hippotragini, Alcelaphini, Reduncini (including Pelea), Aepyceros possibly linked to Neotragus, and Cephalophini possibly linked to Oreotragus (the suni and the klipspringer being members of a polyphyletic Neotragini). These various tribes and major lineages were produced by two noteworthy explosive radiations, which occurred simultaneously between 12.0 and 15.3 MY (Middle Miocene) in the subfamilies Bovinae and Antilopinae.     

Phylogenetic relationships among Nearctic shrews of the genus Sorex (Insectivora, Soricidae) inferred from combined cytochrome b and inter-SINE fingerprint data using Bayesian analysis

The field of molecular systematics has relied heavily on mitochondrial DNA (mtDNA) analysis since its inception. Despite the obvious utility of mtDNA, such data inevitably only presents a limited (i.e., single genome) perspective on species evolution. A combination of mitochondrial and nuclear markers is essential for reconstructing more robust phylogenetic trees. To evaluate the utility of one category of nuclear marker (short interspersed elements or SINEs) for resolving phylogenetic relationships, we constructed an inter-SINE fingerprint for nine putative species of the genus Sorex. In addition, we analyzed 1011 nucleotides of the cytochrome b gene. Traditional neighbor-joining and maximum parsimony analyses were applied to the individual cytochrome b and inter-SINE fingerprint data sets, along with Bayesian analysis to the combined data sets. We found inter-SINE fingerprinting to be an effective species level marker; however, we were unable to reconstruct deeper branching patterns within the Sorex genus using these data. The combined data analyzed under a Bayesian analysis showed higher levels of structuring within the Otisorex subgenus, most notably recognizing a monophyletic group consisting of sister-taxa S. palustris and S. monticolus, S. cinereus and S. haydeni, and S. hoyi. An additional noteworthy result was the detection of an historic mitochondrial introgression event between S. monticolus and S. palustris. When combining disparate data sets, we emphasize researcher diligence as certain types of data and processes may overly influence the analysis. However, there is considerable phylogenetic potential stemming from inter-SINE fingerprinting.     

Molecular evolutionary dynamics of cytochrome b in strepsirrhine primates: the phylogenetic significance of third-position transversions

DNA sequences of the complete cytochrome b gene are shown to contain robust phylogenetic signal for the strepsirrhine primates (i.e., lemurs and lorises). The phylogeny derived from these data conforms to other molecular studies of strepsirrhine relationships despite the fact that uncorrected nucleotide distances are high for nearly all intrastrepsirrhine comparisons, with most in the 15%-20% range. Cytochrome b sequences support the hypothesis that Malagasy lemuriforms and Afro-Asian lorisiforms each comprise clades that share a sister- group relationship. A study (Adkins and Honeycutt 1994) of the cytochrome c oxidase subunit II (COII) gene placed one Malagasy primate (Daubentonia) at the base of the strepsirrhine clade, thereby suggesting a diphyletic Lemuriformes. The reanalysis of COII third- position transversions, either alone or in combination with cytochrome b third-position transversions, however, yields a tree that is congruent with phylogenetic hypotheses derived from cytochrome b and other genetic data sets.      

斗鱼属鱼类亲缘关系的Cyt b基因序列和RAPD分析

采用mtDNA Cyt b基因序列分析和RAPD两种分子标记技术,研究了中国分布的叉尾斗鱼(Macropodus opercularis)、圆尾斗鱼(M.chinensis)和香港斗鱼(M.hongkongensis)以及越南的红鳍斗鱼(M.erythropterus)4种鱼类之间的亲缘关系.获得4种斗鱼14条Cyt b基因全序列(1 155 bp),结合GenBank中搜索到的近缘物种同源序列进行分析.从133条随机引物中筛选到36条引物,在优化的反应条件下,10个群体96个个体共扩增出清晰稳定的条带749条,构建矩阵进行分析和聚类.基于Cyt b全序列以邻接法和最小进化法构建的系统树及RAPD数据UPGMA聚类分析的结果都显示,香港斗鱼和红鳍斗鱼先聚为一分支,再与叉尾斗鱼聚类,圆尾斗鱼处于外缘.本研究结果反映了圆尾斗鱼与其他斗鱼的亲缘关系较远,种间遗传距离为0.184 5～0.225 3(Cyt b)和0.653 6～0.746 5(RAPD),两者为同一单系群中两个独立演化的自然类群;香港斗鱼与叉尾斗鱼间遗传分化明显,Cyt b碱基差异为11.00%,RAFD遗传距离达0.577 7,支持其为独立物种的观点,且香港斗鱼群体间遗传差异较大,Cyt b碱基差异为3.12%,RAPD遗传距离0.060 1;叉尾斗鱼群体间Nei's基因多样度和Shannon信息指数分别为0.058 2和0.086 9,而各群体内的数值分别为0.016 1～0.031 7和0.023 5～0.046 7,表明遗传差异主要来自群体间,并按分布流域分别聚类.     

Phylogeny of the Gadidae (sensu Svetovidov, 1948) based on their morphology and two mitochondrial genes

Although Codfishes are probably one of the most studied groups of all teleost fishes worldwide owing to their great importance to fisheries, their phylogeny and classification are still far from being firmly established. In this study, we present phylogenetic relationships of 19 out of 22 genera traditionally included in the Gadidae based on the analysis of entire cytochrome b and partial cytochrome oxidase I genes (1530 bp). Maximum Parsimony, Maximum Likelihood, and Bayesian analyses all recovered five main clades that correspond to traditionally recognized groupings within Gadoids. The same clades were recovered with MP analysis based on 30 morphological characters (collected from the literature). Given these findings, we propose a revised provisional classification of Gadoids: one suborder Gadoidei containing two families, the Merlucciidae (1 genus) and the Gadidae (21 genera) distributed into four subfamilies: the Gadinae (12 genera), the Lotinae (3 genera), the Gaidropsarinae (3 genera), and the Phycinae (3 genera). Lastly, nuclear inserts of mitochondrial DNA (Numts) were identified in two species, i.e., Gadiculus argenteus and Melanogrammus aeglefinus.     

Relative patterns and rates of evolution in heron nuclear and mitochondrial DNA

Mitochondrial cytochrome b sequence data from 15 species of herons (Aves: Ardeidae), representing 13 genera, were compared with DNA hybridization data of single-copy nuclear DNA (scnDNA) from the same species in a taxonomic congruence assessment of heron phylogeny. The two data sets produced a partially resolved, completely congruent estimate of phylogeny with the following basic structure: (Tigrisoma, Cochlearius, (((Zebrilus, (Ixobrychus, Botaurus)), (((Ardea, Casmerodius), Bubulcus), ((Egretta thula, Egretta caerulea, Egretta tricolor), Syrigma), Butorides, Nycticorax, Nyctanassa)))). Because congruence indicated similar phylogenetic information in the two data sets, we used the relatively unsaturated DNA hybridization distances as surrogates of time to examine graphically the patterns and rates of change in cytochrome b distances. Cytochrome b distances were computed either from whole sequences or from partitioned sequences consisting of transitions, transversions, specific codon site positions, or specific protein-coding regions. These graphical comparisons indicated that unpartitioned cytochrome b has evolved at 5-10 times the rate of scnDNA. Third-position transversions appeared to offer the most useful sequence partition for phylogenetic analysis because of their relatively fast rate of substitution (two times that of scnDNA) and negligible saturation. We also examined lineage-based rates of evolution by comparing branch length patterns between the nuclear and cytochrome b trees. The degree of correlation in corresponding branch lengths between cytochrome b and DNA hybridization trees depended on DNA sequence partitioning. When cytochrome b sequences were not partitioned, branch lengths in the cytochrome b and DNA hybridization trees were not correlated. However, when cytochrome b sequences were reduced to third-position transversions (i.e., unsaturated, relatively fast changing data), branch lengths were correlated. This finding suggests that lineage-based rates of DNA evolution in nuclear and mitochondrial genomes are influenced by common causes.     

Sequence evolution and phylogenetic signal in control-region and cytochrome b sequences of rainbow fishes (Melanotaeniidae)

The nucleotide sequences of segments of the cytochrome b gene (351 bp), the tRNA(Pro) gene (49 bp), and the control region (approximately 313 bp) of mitochondrial DNA were obtained from 26 fish representing different populations and species of Melanotaenia and one species of Glossolepis, freshwater rainbow fishes confined to Australia and New Guinea. The purpose was to investigate relative rates and patterns of sequence evolution. Overall levels of divergence were similar for the cytochrome b and tRNA control-region sequences, both ranging from < 1% within subspecies to 15%-19% between genera. However, the patterns of sequence evolution differed. For the cytochrome b gene, transitions consistently exceeded transversions, the bias ranging from 4.2:1 to 2:1, depending on the level of sequence divergence. However, in the control-region sequence, a bias toward transitions (2:1) was observed only in comparisons between very similar sequences, and transversions outnumbered transitions in comparisons of divergent sequences. Graphic comparisons suggested that the control region was saturated for transitions at relatively low levels of sequence divergence but accumulated transversions at a greater rate than did the cytochrome b sequence. These distinct patterns of base substitution are associated with differences in A+T content, which is 70% for the tRNA control- region segment versus 50% for cytochrome b. A test for skewness in the distribution of lengths of random trees indicated that both segments contained phylogenetic signal. Parsimony analyses of the data from the two regions, with or without weighting schemes appropriate to the respective patterns of sequence evolution, identified the same five groupings of sequences, but the relationships among the groups differed. However, in most cases the branches uniting different combinations of groups were poorly supported, and the differences among topologies were insignificant. Considering the observed patterns of base substitution and the results of the phylogenetic analyses, we deduce that both the control region and cytochrome b are appropriate for population genetic studies but that the control region is less effective than cytochrome b for resolving relationships among divergent lineages of rainbow fishes.      

Phylogenetic Relationships among Asian species of Petaurista (Rodentia, Sciuridae), Inferred from Mitochondrial Cytochrome b Gene Sequences

To elucidate the phylogenetic relationships among four species belonging to the genus Petaurista (P. alborufus castaneus, P. alborufus lena, P. leucogenys leucogenys, P. leucogenys nikkonis, P. petaurista melanotus, and P. philippensis grandis), we investigated the partial sequences (1,068 bp) of the mitochondrial cytochrome b gene for these giant flying squirrels. Phylogenetic trees (NJ, MP, and ML trees) constructed from cytochrome b sequences indicated that P. leucogenys was grouped independently with other species, and that P. philippensis was most closely related to P. petaurista with 99-100% bootstrap values. In addition, two subspecies of P. alborufus did not form a single clade: P. alborufus castaneus from China was most distantly related to the other species, whereas P. alborufus lena from Taiwan was closely related to P. petaurista and P. philippensis with 82-90% bootstrap values. This result suggests that it is reasonable to regard P. alborufus lena as a distinct species from P. alborufus castaneus.     

Expression of outer mitochondrial membrane cytochrome b 5 in Escherichia coli. Purification of the recombinant protein and studies of its interaction with electron-transfer partners

In the present work, we report expression in Escherichia coli, purification, and characterization of recombinant full-length cytochrome b(5) from outer mitochondrial membrane. Optimization of expression conditions for cytochrome b(5) from outer mitochondrial membrane allowed reaching expression level up to 10(4) nmol of the hemeprotein per liter of culture. Recombinant cytochrome b(5) from outer mitochondrial membrane was purified from cell lysate by using metal-affinity chromatography. It has physicochemical, spectral, and immunochemical properties similar to those of cytochrome b(5) from rat liver outer mitochondrial membrane. Immobilized recombinant mitochondrial cytochrome b(5) was used as affinity ligand to study its interaction with electron transfer proteins. By using this approach, it is shown that in interaction of NADPH:cytochrome P450 reductase with both forms of cytochrome b(5) an important role is played by hydrophobic interactions between proteins, although the contribution of these interactions in complex formation with NADPH:cytochrome P450 reductase is different for isoforms of cytochrome b(5).     

Identification of outer mitochondrial membrane cytochrome b5 as a modulator for androgen synthesis in Leydig cells

Outer mitochondrial membrane cytochrome b5 is an isoform of microsomal membrane cytochrome b5. In rat testes the outer mitochondrial membrane cytochrome b5 is present in both mitochondria and microsomes, whereas microsomal membrane cytochrome b5 is undetectable. Outer mitochondrial membrane cytochrome b5 present in the testis was localized in Leydig cells with cytochrome P-45017alpha, which catalyzes androgenesis therein. We therefore analyzed the functions of outer mitochondrial membrane cytochrome b5 in rat testis microsomes by using a proteoliposome system. In a low but physiological concentration of NADPH-cytochrome P-450 reductase and excess amount of progesterone, outer mitochondrial membrane cytochrome b5 stimulated the cytochrome P-45017alpha-catalyzed reactions, 17alpha-hydroxylation and C17-C20 bond cleavage. The effects were different from those by microsomal membrane cytochrome b5 as follows: preferential elevation of the 17alpha-hydroxylase activity by outer mitochondrial membrane cytochrome b5 in an amount-dependent manner versus that of the lyase activity by microsomal membrane cytochrome b5 at the low concentration, and the inhibition of both activities at the high concentration. At a low concentration of progesterone reflecting a physiological cholesterol supply, outer mitochondrial membrane cytochrome b5 elevated primarily the production of 17alpha-hydroxyprogesterone and then facilitated the conversion of the released intermediate to androstenedione. Thus, we demonstrated that outer mitochondrial membrane cytochrome b5 and not microsomal membrane cytochrome b5 functions as an activator for androgenesis in rat Leydig cells.     

从细胞色素b基因序列变异分析中国鲇形目鱼类的系统发育

采用PCR技术获得中国鲇形目鱼类11科24属27个代表种类细胞色素b基因1138bp全序列,比较分析了来自北美洲、非洲的部分鲇形目鱼类同一基因序列,并选取脂鲤目、鲤形目和鲱形目鱼类作外类群,采用Bayesian方法和最大简约法(MP)构建分子系统树。结果表明：(1)鲇形目鱼类细胞色素b基因序列中,与脂鲤目、鲤形目以及鲱形目鱼类相比存在3bp的缺失;(2)鲇形目鱼类各科代表种类形成一单系群;(3)两种建树方法均支持铫科、粒鲇科和钝头鮠科形成一单系群;而胡子鲇科、刀鲇科、海鲇科、鮰科、长臀鮠科、鲢科、鲇科、棘脂鲿科、鲿科形成一大的单系群;但鳗鲇科的系统位置两种建树方法没有取得一致结果;而其中长臀鲍科与北美的鮰科形成姐妹群,胡子鲇、鮰科、鲇科、鲿科和鮡科是较明显的单系群。     

A maximum-likelihood analysis of eight phylogenetic markers in gallwasps (Hymenoptera: Cynipidae): implications for insect phylogenetic studies

We assessed the utility of eight DNA sequence markers (5.8S rDNA, 18S rDNA, 28S rDNA, ITS regions, long-wavelength opsin, elongation factor 1-alpha, cytochrome b, and cytochrome oxidase I) in reconstructing phylogenetic relationships at various levels of divergence in gallwasps (Hymenoptera: Cynipidae), using a set of eight exemplar taxa. We report sequence divergence values and saturation levels and compare phylogenetic results of these sequences analyzed both separately and combined to a well-corroborated morphological phylogeny. Likelihood ratio tests were used to find the best evolutionary model fitting each of the markers. The likelihood model best explaining the data is, for most loci, parameter rich, with strong A-T bias for mitochondrial loci and strong rate heterogeneity for the majority of loci. Our data suggest that 28S rDNA, elongation factor 1-alpha, and long-wavelength opsin may be potentially useful markers for the resolution of cynipid and other insect within-family-level divergences (circa 50-100 mya old), whereas mitochondrial loci and ITS regions are most useful for lower-level phylogenetics. In contrast, the 18S rDNA marker is likely to be useful for the resolution of above-family-level relationships.     

几种鳄分子系统发生的探讨

百年来关于扬子鳄的分类学位置存在着很多争议,本测得扬子鳄、暹罗鳄和湾鳄的mtDNA ND4和Cytb基因,并从GenBank中获得密西西比鳄和海龟的DN4基因和Cytb基因相应片段。用Clustal X1.8进行对位排列,以海龟为外群构建分子进化系统树。结果显示,在鳄类动物中,扬子鳄与密西西比鳄的亲缘关系最近,两ND4基因序列碱基差异的20．68％,而Cytb基因序列碱基差异为14．43％,但扬子鳄与密西西相比与鳄的分类问题仍将有待进一步探讨。     

Multi‐gene phylogeny of jacks and pompanos (Carangidae), including placement of monotypic vadigo Campogramma glaycos

In this study, the phylogenetic trees of jacks and pompanos (Carangidae), an ecologically and morphologically diverse, globally distributed fish family, are inferred from a complete, concatenated data set of two mitochondrial (cytochrome c oxidase I, cytochrome b) loci and one nuclear (myosin heavy chain 6) locus. Maximum likelihood and Bayesian inferences are largely congruent and show a clear separation of Carangidae into the four subfamilies: Scomberoidinae, Trachinotinae, Naucratinae and Caranginae. The inclusion of the carangid sister lineages Coryphaenidae (dolphinfishes) and Rachycentridae (cobia), however, render Carangidae paraphyletic. The phylogenetic trees also show with high statistical support that the monotypic vadigo Campogramma glaycos is the sister to all other species within the Naucratinae.     

Nuclear and mitochondrial genes contain similar phylogenetic signal for pigeons and doves (Aves: Columbiformes)

Molecular systematic studies generally assume that gene trees are reasonable estimates of species trees. We tested the validity of this assumption in the pigeons and doves (Aves: Columbiformes) by comparing phylogenies derived from nuclear (beta-fibrinogen intron 7) and mitochondrial (cytochrome b) genes. Trees derived from the two genes when analyzed separately contained many nodes in common. A partition homogeneity test revealed no significant incongruence between trees derived from the two genes; so, we combined nuclear and mitochondrial data in subsequent phylogenetic analyses. The resulting tree, which was highly resolved and generally well supported, contained a strong biogeographic component. The rate of nucleotide substitution for the nuclear intron was approximately six times slower than that of cytochrome b. This resulted in a much higher consistency index for trees derived from the intron because of the low level of multiple substitution. However, the degree of resolution and support for trees reconstructed from the two genes was similar. We also examined the transition and transversion substitution rates for the genes. Third position transversions for cytochrome b accumulated linearly with intron divergence, suggesting low levels of multiple substitution for third position transversions.     

Molecular phylogeny of a cosmopolitan group of woodpeckers (genus Picoides) gased on COI and cyt b mitochondrial gene sequences.

Picoides is the largest genus of woodpeckers and member species are found on most major land masses. Current systematic arrangement of this group, based on morphological, behavioral, and plumage characters, suggests that New World species evolved from a single invasion by a Eurasian common ancestor and that all New World species form a monophyletic group. No clear link has ever been established between the relationships of Old World and New World species other than to infer that the most primitive species is Eurasian. This study employs DNA sequences for two protein-coding mitochondrial genes, cytochrome oxidase I and cytochrome b, to reconstruct phylogenetic relationships among all New World species and several Eurasian representatives of the genus Picoides. A well-resolved mitochondrial gene tree is in direct conflict with proposed species relationships based on nongenetic characters; monophyly among New World species is rejected, the evolution of New World species likely resulted from as many as three independent Eurasian invasions, and Picoides is paraphyletic with two other woodpecker genera, Veniliornis and Dendropicos. These results strongly suggest that this large, cosmopolitan genus is in need of systematic revision in order to reflect evolutionary history.     

Resolution of phylogenetic relationships among recently evolved species as a function of amount of DNA sequence: an empirical study based on woodpeckers (Aves: Picidae)

Synonymous substitutions in the 13 mitochondrial encoded protein genes form a large pool of characters that should approach the ideal for phylogenetic analysis of being independently and identically distributed. Pooling sequences from multiple mitochondrial protein-coding genes should result in statistically more powerful estimates of relationships among species that diverged sufficiently recently that most nucleotide substitutions are synonymous. Cytochrome oxidase I (COI) was sequenced for woodpecker species for which cytochrome b (cyt b) sequences were available. A pairing-design test based on the normal distribution indicated that cyt b evolves more rapidly than COI when all nucleotides are compared but their rates are equal for synonymous substitutions. Nearly all of the phylogenetically informative substitutions among woodpeckers are synonymous. Statistical support for relationships, as measured by bootstrap proportions, increased as the number of nucleotides increased from 1047 (cyt b) to 1512 (COI) to 2559 nucleotides (aggregate data set). Pseudo-bootstrap replicates showed the same trend and increasing the amount of sequence beyond the actual length of 2559 nucleotides to 5120 (2x) resulted in stronger bootstrap support, even though the amount of phylogenetic information was the same. However, the amount of sequence required to resolve an internode depends on the length of the internode and its depth in the phylogeny.     

Mitochondrial cytochrome b Sequence Variation and Phylogenetics of the Highly Specialized Schizothoracine Fishes (Teleostei: Cyprinidae) in the Qinghai-Tibet Plateau

The complete 1140 bp mitochondrial cytochrome b sequences were obtained from 39 individuals representing five species of all four genera of highly specialized schizothoracine fishes distributed in the Qinghai-Tibet plateau. Sequence variation of the cytochrome b gene was surveyed among the 39 individuals as well as three primitive schizothoracines and one outgroup. Phylogenetic analysis suggested that the group assignment based on 1140 bp of the cytochrome b sequence is obviously different from previous assignments, and the highly specialized schizothoracine fishes (Schizopygopsis pylzovi, Gymnocypris przewalskii, G. eckloni, Chuanchia labiosa, and Platypharodon extremus) form a monophyletic group that is sister to the clade formed by the primitive schizothoracine fishes (Schizothorax prenanti, S. pseudaksaiensis, and S. argentatus). The haplotypes of Schizopygopsis pylzovi and G. przewalskii were paraphyletic based on cytochrome b data, which most likely reflected incomplete sorting of mitochondrial DNA lineages. The diploid chromosome numbers of Schizothoracinae were considered in phylogenetic analysis and provided a clear pattern of relationships. Molecular dating estimated for highly specialized schizothoracine fishes suggested that the highly specialized schizothoracine fishes diverged in the late Miocene Pliocene to Pleistocene (4.5 × 10⁴–4.05 × 10⁶ years BP). The relationship between the cladogenesis of highly specialized schizothoracine fishes and geographical events of the Qinghai-Tibet plateau is discussed.     

Morphological and mitochondrial DNA characters for identification and phylogenetic analysis of the myiasis-causing flesh fly Wohlfahrtia magnifica and its relatives, with a description of Wohlfahrtia monegrosensis sp. n. Wyatt & Hall

Abstract.  Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae) is a major cause of traumatic myiasis in livestock in Central and Eastern Europe and in countries bordering the Mediterranean. The present study explored the utility of external body characters, genitalia characters and mitochondrial DNA characters for identification of this and related species in the subfamily Paramacronychiinae. Sequence analyses of the 3' terminal 273 bp of the mitochondrial cytochrome b gene revealed two lineages of W. magnifica , one from Spain and France and the other from the rest of Eurasia, differing by only two base pairs. Phylogenetic analysis of cytochrome b showed that W. magnifica and Wohlfahrtia vigil Walker were sister species; this conclusion was not contradicted by a phylogenetic analysis of the morphological characters. Based on cytochrome b , the genetic distance between specimens of W. vigil from Europe and North America was sufficiently large to justify the recognition of more than one species. A new species, Wohlfahrtia monegrosensis , from northern Spain, was described, based on morphology and cytochrome b . A unique combination of external body characters of males or females were diagnostic for W. magnifica , the W. vigil group and Wohlfahrtia bella , but only the genitalia characters were diagnostic for all nine species studied.     

The largemouth bass cytochrome b gene

The cytochrome b gene is one of the protein-coding genes of the mitochondrial genome that has gained importance because of the ease with which molecular techniques can be applied to the analysis of its structure. The nucleotide sequence of the largemouth bass ( Microplerus salmoides ) cytochrome b gene was determined and the inferred amino acid structure is presented in the form of a structural model derived originally from rat cytochrome b . The inferred amino acid sequences from divergent animal species are aligned and compared in the context of this model. The data suggest that regions of the gene may be evolving at different rates due to different selection pressures associated with functional constraints. Conserved and variable regions of cytochrome b have been identified and can be targeted for species identification, the examination of intraspeciflc variation, and phylogenetic reconstructions in future research.