Cytochrome Oxidase Subunit II Gene Research Articles

Disclosure of genetic diversity of mackerel fish (Scomberomorus spp.) in Indonesian waters based on the mitochondrial cytochrome oxidase subunit II (COII) gene.

Mackerel fish (Scomberomorus spp.) represents a significant marine fisheries commodity in Indonesia, characterized by its high commercial value and nutritional content. To understand the intraspecific interactions and genetic variability of Scomberomorus spp., a more extensive research of Scomberomorus spp. populations, including both cultivated and wild specimens, is required. This study aimed to explore the genetic diversity of mackerel fish in Indonesian waters, focusing on the mitochondrial DNA (mtDNA) cytochrome oxidase subunit II (COII) gene, which encodes the second subunit of cytochrome c oxidase (complex IV), is essential for aerobic respiration and energy transformation. Muscle tissue samples from 18 individual mackerel fish collected from various regions in Indonesia, including Palembang, Cilacap, Rembang, Banjarmasin, Ambon, and Fak-Fak Regencies, were utilized. The genomic DNA was isolated and amplified using specific primers: CO2TF (5'-ACCGCTCTGTCACTTTCTTC-3') and CO2TR (5'-ATGTCACTAAGGGTGGTTGG-3'). Subsequently, the obtained amplicons were subjected to sequencing. The sequence data were then analyzed using the MEGA11 and DnaSP 6 software. Our findings revealed 120 variable sites within the 691 base pairs of mtDNA COII sequences, resulting in a nucleotide diversity (Pi) of 0.07169. Furthermore, we identified eight haplotypes, demonstrating a haplotype diversity (Hd) of 0.8889. Remarkably, all mackerel samples from Palembang and Cilacap clustered into discrete haplotypes, specifically haplotype 1 and haplotype 2, respectively. Our phylogenetic analysis delineated three distinct clades. Clade I, closely related to Scomberomorus cavalla, encompassed all individuals from Ambon, Palembang, Rembang, and one from Banjarmasin. Clade II, associated with Scomberomorus niphonius, included individuals from Cilacap and two from Banjarmasin. Clade III, linked to Scomberomorus semifasciatus, exclusively consisted of individuals from Fak-Fak (Papua). In conclusion, Indonesian waters harbor diverse genetic variations within Scomberomorus spp., and population relationships based on the mtDNA COII gene exhibit notable complexities. Future research endeavors should focus on further elucidating the diversity and relationships among Scomberomorus spp. in diverse Indonesian populations.

Cytochrome Oxidase Subunit II: Potential Marker for the Identification of Forensically Significant Species of Coleoptera—A Preliminary Study

The foremost concern in forensic entomology is the explicit identification of the species recovered from the crime scene. From the different orders of insects, Diptera is the prime focus in this field, followed by Coleoptera, whose identification can be extremely helpful for corpses in later decomposition stages. In this study, cytochrome oxidase subunit II (COII) was used to check its adequacy as a genetic marker and to create a reference database for eleven species belonging to five families of Coleoptera, namely, Silphidae, Staphylinidae, Histeridae, Dermestidae and Scarabaeidae, from two different states in India to assist in the accurate identification of imperative beetle species in medico-legal entomology. To achieve this, standard protocols of DNA isolation, amplification and sequencing were followed. We concluded that the COII gene can be used as a molecular marker for the identification of forensically relevant species, as observed from the similarities between the phylogenetic relationship constructed by COII and morphological data.

Study on the Genetic Differentiation of Geographic Populations of Calliptamus italicus (Orthoptera: Acrididae) in Sino-Kazakh Border Areas Based on Mitochondrial COI and COII Genes.

Calliptamus italicus L. is an important pest on the desert and semidesert steppes along the Sino-Kazakh border. To elucidate the molecular mechanism of its continuous outbreaks, we studied 11 different geographic populations of C. italicus to determine: 1) the complete sequences of the entire mitochondrial cytochrome oxidase subunit I (COI) and mitochondrial cytochrome oxidase subunit II (COII) genes, and 2) performed genetic diversity, differentiation, gene flow, and molecular variation analyses. Of the 11 populations, the Yining County (YNX) population had the highest haplotype diversity and Pi values. There are significant differences in Tajima’s D and Fu’s Fs (P < 0.05). The fixation index Fst values of the total C. italicus population were 0.03352, and its gene flow Nm values of the total C. italicus population were 15.32. Taken together, there were five main findings: 1) the current genetic differentiation of C. italicus arose within populations; 2) genetic exchange levels were high between geographical populations; 3) genetic variation level was low; 4) C. italicus populations likely expanded in recently, and 5) there was no significant correlation between genetic distance and geographic distance for any geographic population. Findings from this study indicate that frequent gene exchange between populations may enhance the adaptability of C. italicus along the Sino-Kazakh border, leading to frequent outbreaks.

Morphological and Genetic Evidence for the Synonymy ofReticulitermesSpecies:Reticulitermes dichrousandReticulitermes guangzhouensis(Isoptera: Rhinotermitidae)

The taxonomy of Reticulitermes Holmgren (Isoptera: Rhinotermitidae) in China is problematic and in need of revision. Most Chinese Reticulitermes species were described in the 1980s and 1990s, and have never been studied since then. In this study, morphological characteristics including coloration, pilosity, shape, and morphometric characteristics of Reticulitermes dichrous Ping and Reticulitermes guangzhouensis Ping were compared. In addition, a portion of the ribosomal RNA large subunit 16S (16S rRNA) and the mitochondrial DNA cytochrome oxidase subunit II (COII) genes from different populations of the 2 species were sequenced and analyzed. Morphological comparisons revealed the similarities between the 2 species in both discrete and morphometric characteristics. In the molecular phylogenetic trees inferred from COII and 16S rRNA genes, all of the examined populations of the 2 species clustered into a common clade with a high bootstrap value. Based on the morphological comparisons and the molecular analyses, it is proposed that R. dichrous is a junior synonym of R. guangzhouensis.

Mitochondrial DNA-based genetic diversity of Anopheles nivipes in North East India

Malaria is a major public health problem in north-east India mainly transmitted by Anopheles baimai and An. minimus while Anopheles nivipes plays an important supportive role. The genetic diversity of An. nivipes in north-east India was investigated by employing two mitochondrial DNA markers namely NADH dehydrogenase 5 (ND5) and cytochrome oxidase sub unit II (COII). High genetic diversity in An. nivipes was observed by the detection of 16 haplotypes among 30 sequences of ND5 gene and 29 haplotypes among 29 COII sequences. Anopheles nivipes of north-east India was significantly differentiated genetically with that of neighboring South-east Asian An. nivipes as revealed by pairwise FST values of 0.127 (p < 0.01) and 0.044 (p < 0.001) for ND5 and COII genes, respectively, suggesting geographical barriers to gene flow in this species between the two geographical areas resulting in significant population structuring.

PCR-RFLP-based method for reliable discrimination of cryptic species within Mecinus janthinus species complex (Mecinini, Curculionidae) introduced in North America for biological control of invasive toadflaxes

Several populations of the stem-mining weevil Mecinus janthinus Germar species complex (Mecinini, Curculionidae), identified based on morphological characteristics, have been introduced in North America for the biological control of invasive toadflaxes of European origin: Linaria vulgaris Miller and L. dalmatica (L.) Miller (Plantaginaceae). According to the mitochondrial cytochrome oxidase subunit II (COII) gene haplotype divergence of Mecinus janthinus species complex, a total of 20 M. janthinus s.s., 3 M. janthinus s.l. of the ‘speciosa’ genotype and 29 M. janthiniformis haplotypes have been recorded across their native range in central and southeastern Europe. A polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) diagnostic assay of COII gene using Hpy188III and MnlI enzyme-mix, was developed for fast and cost-effective discrimination of these morphologically very similar cryptic weevil species. It is shown that digestion generates unique 4-fragment restriction profile in M. janthinus s.s., 2-fragment profile in M. janthiniformis and 3-fragment profile in M. janthinus s.l. ‘speciosa’ group of haplotypes, allowing precise identification of each species or genotype. The proposed method represents a practical tool for fast and accurate identification of the target biocontrol agents and should prevent using inappropriate weevil species in redistribution programs for biological control of invasive toadflax species.

Genetic population structure of the malaria vector Anopheles baimaii in north-east India using mitochondrial DNA

BackgroundAnopheles baimaii is a primary vector of human malaria in the forest settings of Southeast Asia including the north-eastern region of India. Here, the genetic population structure and the basic population genetic parameters of An. baimaii in north-east India were estimated using DNA sequences of the mitochondrial cytochrome oxidase sub unit II (COII) gene.MethodsAnopheles baimaii were collected from 26 geo-referenced locations across the seven north-east Indian states and the COII gene was sequenced from 176 individuals across these sites. Fifty-seven COII sequences of An. baimaii from six locations in Bangladesh, Myanmar and Thailand from a previous study were added to this dataset. Altogether, 233 sequences were grouped into eight population groups, to facilitate analyses of genetic diversity, population structure and population history.ResultsA star-shaped median joining haplotype network, unimodal mismatch distribution and significantly negative neutrality tests indicated population expansion in An. baimaii with the start of expansion estimated to be ~0.243 million years before present (MYBP) in north-east India. The populations of An. baimaii from north-east India had the highest haplotype and nucleotide diversity with all other populations having a subset of this diversity, likely as the result of range expansion from north-east India. The north-east Indian populations were genetically distinct from those in Bangladesh, Myanmar and Thailand, indicating that mountains, such as the Arakan mountain range between north-east India and Myanmar, are a significant barrier to gene flow. Within north-east India, there was no genetic differentiation among populations with the exception of the Central 2 population in the Barail hills area that was significantly differentiated from other populations.ConclusionsThe high genetic distinctiveness of the Central 2 population in the Barail hills area of the north-east India should be confirmed and its epidemiological significance further investigated. The lack of genetic population structure in the other north-east Indian populations likely reflects large population sizes of An. baimaii that, historically, were able to disperse through continuous forest habitats in the north-east India. Additional markers and analytical approaches are required to determine if recent deforestation is now preventing ongoing gene flow. Until such information is acquired, An. baimaii in north-east India should be treated as a single unit for the implementation of vector control measures.

Phylogeny of Rhus gall aphids (Hemiptera : Pemphigidae) based on combined molecular analysis of nuclear EF1α and mitochondrial COII genes

Abstract Rhus gall aphids (Fordinae : Melaphidini) have a disjunct distribution in East Asia and North America and have specific host plant relationships. Some of them are of economic importance and all species form sealed galls which show great variation in shape, size, structure, and galling‐site. We present a phylogeny incorporating ten species and four subspecies of Rhus gall aphids based on 1694 base pairs of nuclear elongation factor‐1α (EF1α) and mitochondrial cytochrome oxidase subunit II (COII) DNA sequence data. The results suggest that Melaphidini is monophyletic and at the genus level, Schlechtendalia, Nurudea, and Floraphis were each monophyletic. Kaburagia and Meitanaphis were not monophyletic and therefore inconsistent with the current classification. The North American sumac gall aphid, Melaphis rhois, was most closely related to the East Asian Floraphis species, although this was poorly supported. The conservation of gall morphology with respect to aphid phylogeny rather than their host plants suggests that gall morphology is largely determined by the aphids. While there is no evidence of strict co‐speciation between the aphids and their primary host plants, switching between recently diverged host plants may be involved in the speciation process in Melaphidini.

Limited variation in mitochondrial DNA of maize-associated Ostrinia nubilalis (Lepidoptera: Crambidae) in Russia, Turkey and Slovenia

A sequence analysis of the mitochondrial cytochrome oxidase subunit II (COII) gene in Russian and Turkish maize- associated populations of Ostrinia nubilalis and a Slovenian population of O. nubilalis probably infesting maize revealed little diver- sity. This lack of diversity may have resulted from bottleneck event(s) when the maize-associated population of O. nubilalis expanded from small population(s) in association with the cultivation of maize in Europe ca. 500 years ago. In the genealogy of COII genes obtained in the present and previous studies, Eurasian samples were substantially differentiated from North American samples. Since the North American population of O. nubilalis came from Europe, our finding suggests that there is geographical dif- ferentiation in European maize-associated O. nubilalis, and that maize-associated populations of O. nubilalis expanded multiple times in Europe. Finally, a phylogenetic analysis of the COII gene did not support that O. nubilalis and O. furnacalis are the closest relatives within the O. furnacalis species group.

Two mitochondrial lineages occur in the Asian corn borer,Ostrinia furnacalis(Lepidoptera: Crambidae), in Japan

The genealogy and diversity of the mitochondrial cytochrome oxidase subunit II (COII) gene were investigated for Ostrinia furnacalis in Japan. A preliminary examination of mitochondrial lineages in China and the Philippines was also made. Two lineages (A and B) were found in the COII gene. Lineage A was frequent throughout the Japanese main islands (Hokkaido, Honshu, Shikoku and Kyushu), while the frequency of lineage B varied among these islands. No clear patterns of geographical population structure were found. Population genetic features suggested that the O. furnacalis population harboring the lineage A mitochondria expanded in the recent past, while lineage B showed weak signals of a population expansion. It is not clear whether the two lineages of mtDNA evolved in separate or identical geographical regions. We discuss two hypotheses regarding the two lineages of mtDNA: a cryptic race/species hypothesis and a selective sweep hypothesis.

The molecular events occur during MK-801-induced cytochrome oxidase subunit II down-regulation in GT1-7 cells

Previously, we showed that predominant expression of the N-methyl-D-aspartate (NMDA) receptor in the neurons of the sexually dimorphic nucleus of the preoptic area of male rats plays an important role in preventing neurons from apoptosis during sexual development. Blocking of the NMDA receptor by dizocilpine ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d] cyclohepten-5,10-iminemaleate (MK-801) causes down-regulation of some survival-related genes including cytochrome oxidase subunit II (COII), a mitochondria-encoded complex IV subunit, which in turn induces ATP depletion and the occurrence of apoptosis. The aim of this study is to investigate the molecular events during down-regulation of the COII gene expression induced by blocking of the NMDA receptor. Treatment of the GnRH cell line (GT1-7) with MK-801 caused 1) a decrease of intracellular calcium concentration ([Ca2+]i) after 20 h; 2) significant decreases of the levels of peroxisome proliferator-activated receptor coactivator-1 (PGC-1) mRNA and protein after 24 h; 3) down-regulation of COII mRNA after 36 h; and 4) the occurrence of neuronal apoptosis after 48 h. Accordingly, we hypothesize that blocking of the NMDA receptor may cause a decrease of the [Ca2+]i, which in turn inhibits the expressions of PGC-1 and COII and then leads to subsequent neuronal apoptosis.

The complete sequence of mitochondrial COII gene of Fenneropenaeus chinensis and its applicability as a marker for phylogenetic analysis

The complete mitochondrial cytochrome oxidase subunit II (COII) gene of Penaeinae shrimp Fenneropenaeus chinensis was cloned and sequenced. The gene is 688 bp in length and codes for 229 amino acids. It shows 83.2%, 87.0% and 83.8% sequence similarity to Marsupenaeus japonicus, Penaeus monodon and Farfantepenaeus notialis, respectively. The A+T content of the whole gene and that at the third position of codons are 64.7% and 78.2%, respectively. The phylogenetic relationship between F. chinensis and three other species representing genera Farfanatepenaeus, Marsupenaeus and Penaeus was analyzed. Results showed that the genetic distances among the four taxa ranged from 0.144 0 to 0.200 5, exceeding those estimated with COI and partial 16S rRNA gene sequences among Marsupenaeus, Litopenaeus and Melicertus, and being therefore larger than the value among subgenera. It has been suggested that the COII gene has a faster evolutionary rate than that of the COI gene and partial 16S rRNA gene and could be used for phylogenetic analysis at genus or species level. The results of the present study indicated that Farfantepenaeus, Fenneropenaeus, Marsupenaeus and Penaeus are at a higher phylogenetic level than subgenus, which supports the opinion of the elevation of phylogenetic status of the four subgenera to genus level.

Molecular phylogeny of the subgenus Drosophila (Diptera, Drosophilidae) with an emphasis on Neotropical species and groups: A nuclear versus mitochondrial gene approach

The genus Drosophila has played an essential role in many biological studies during the last 100 years but much controversy and many incompletely addressed issues still remain to be elucidated regarding the phylogeny of this genus. Because information on the Neotropical species contained in the subgenus Drosophila is particularly incomplete, with this taxonomic group being underrepresented in many studies, we designed a study to answer some evolutionary questions related to these species. We subjected at least 41 Drosophilidae taxa to a phylogenetic analysis using a 516-base pair (bp) fragment of the α-methyldopa ( Amd) nuclear gene and a 672 bp fragment of the mitochondrial cytochrome oxidase subunit II ( COII) gene both individually and in combination. We found that the subgenus Drosophila is paraphyletic and subdivided into two main clusters: the first containing species traditionally placed in the virilis-repleta radiation and the second assembling species of the immigrans-Hirtodrosophila radiation. Inside the first of these clusters we could detect the monophyly of both the flavopilosa (the sister-clade of the annulimana group) and the mesophragmatica (closely related to the repleta group) species groups. Concerning the immigrans-Hirtodrosophila lineage, Zaprionus, Liodrosophila, Samoaia, and Hirtodrosophila were the early offshoots, followed by the immigrans, quinaria, testacea, and funebris species groups. The tripunctata radiation appears to be a derived clade, composed of a paraphyletic tripunctata group, intimately interposed with members of the cardini, guarani, and guaramunu species groups. Overall, the COII gene yielded a poor phylogenetic performance when compared to the Amd gene, the evolutionary hypothesis of which agreed with the total evidence tree. This phenomenon can be explained by the fast saturation of transitional substitutions in COII, due to strong biases in both base composition and substitution patterns, as also by its great among-site rate variation heterogeneity.

Sources of Incongruence among Mammalian Mitochondrial Sequences: COII, COIII, and ND6 Genes Are Main Contributors

To investigate the origins of incongruence among mammalian mitochondrial protein-coding genes, we compiled a matrix that included 13 protein-coding-genes for 41 mammals from 14 different orders. This matrix was examined for congruence using different partitioning strategies. The incongruence length difference test showed significant incongruence among the 13 gene partitions used simultaneously, and the result was not affected by third codon or transversion weighting. In the pair-wise comparisons, significant incongruence was detected between NADH:ubiquinone oxidoreductase subunit 6 gene (ND6), cytochrome oxidase subunit II (COII), or cytochrome oxidase subunit III (COIII) gene partitioned individually against the rest of the genes. Omission of any of the 14 mammalian orders alone or in combinations from the matrix did not result in a statistically significant improvement of congruence, suggesting that taxonomic sampling will not improve congruence among the data sets. However, omission of the ND6, COII, and COIII significantly improved congruence in our data matrix. Possible origins of unusual phylogenetic properties of the three genes are discussed.

Molecular phylogeny of cockroaches (Blattaria) based on mitochondrial COII gene sequences

SummaryPhylogenetic relationships among five cockroach families (Cryptocercidae, Polyphagidae, Blattidae, Blattellidae and Blaberidae) using seventeen species, were estimated based on the DNA sequences of the mitochondrial cytochrome oxidase subunit II (COII) gene. A cladogram inferred using the neighbour‐joining method indicated that Polyphagidae and Cryptocercidae are closely related to each other, and that these two groups are a sister group to the remaining cockroach families. The monophyly of this clade, however, was not strongly supported in terms of bootstrap percentages. Blaberidae and Blattellidae were shown to be sister groups as previously proposed, with Blattidae as a sister group to that clade. Non‐weighted and weighted parsimony analyses were also performed following analyses of nucleotide substitution patterns that indicated saturation of the COII gene among these taxa had occurred. These parsimonious cladograms suggested that Polyphagidae was the basal family, and Polyphaginae, including Cryptocercus as proposed by Grandcolas 1994a), was not monophyletic. The inferred relationships among cockroach families (Polyphagidae, Cryptocercidae + (Blattidae + (Blattellidae + Blaberidae))) is partly in agreement with some previously published analyses. Additionally, based on molecular data, Asian and American Cryptocercus are suggested to have diverged from one another before the Oligocene (∼20 mya).

Transcription and editing of cytochrome oxidase II RNAs in Trypanosoma cruzi.

The cytochrome oxidase subunit II (COII) gene is one of the maxicircle cryptogenes of kinetoplastids whose primary transcripts are sometimes modified by RNA editing to produce mature mRNAs. We determined the sequence of the COII gene in three strains of Trypanosoma cruzi (Y, Corpus Christi, and Tulahuén) and examined its developmental expression. Comparison of the RNA and DNA sequences encoding COII indicated that in the three strains of T. cruzi, four uridines are inserted in the pre-mRNA at the same positions as they are in the COII pre-mRNAs of Trypanosoma brucei, Leishmania tarentolae, and Crithidia fasciculata. The putative guide RNA (gRNA) sequence that serves as a template for the four uridine insertions is located in the 3'-untranslated region of the T. cruzi COII mRNA. Analysis of editing intermediates demonstrates that the COII gRNA remains attached to the pre-mRNA while participating in the formation of chimeric RNAs. Northern blots used to investigate stage-specific expression of the COII gene revealed RNAs of 800 and 900 nucleotides, similar in size to those present in T. brucei. In contrast to the differential expression observed in T. brucei, no difference occurs between the COII mRNA levels of insect and mammalian stages of T. cruzi.

Mitochondrial COII sequences and modern human origins.

The aim of this study is to measure human mitochondrial sequence variability in the relatively slowly evolving mitochondrial gene cytochrome oxidase subunit II (COII) and to estimate when the human common ancestral mitochondrial type existed. New COII gene sequences were determined for five humans (Homo sapiens), including some of the most mitochondrially divergent humans known; for two pygmy chimpanzees (Pan paniscus); and for a common chimpanzee (P. troglodytes). COII sequences were analyzed with those from another relatively slowly evolving mitochondrial region (ND4-5). From class 1 (third codon position) sequence data, a relative divergence date for the human mitochondrial ancestor is estimated as 1/27 th of the human-chimpanzee divergence time. If it is assumed that humans and chimpanzees diverged 6 Mya, this places a human mitochondrial ancestor at 222,000 years, significantly different from 1 Myr (the presumed time of an H. erectus emergence from Africa). The mean coalescent time estimated from all 1,580 sites of combined mitochondrial data, when a 6-Mya human-chimpanzee divergence is assumed, is 298,000 years, with 95% confidence interval of 129,000-536,000 years. Neither estimate is compatible with a 1-Myr-old human mitochondrial ancestor. The mitochondrial DNA sequence data from COII and ND4-5 regions therefore do not support this multiregional hypothesis for the emergence of modern humans.

Mitochondrial DNA sequence analysis of the cytochrome oxidase subunit II gene from Podospora anserina: A group IA intron with a putative alternative splice site

A 5 kb region of the 95 kb mitochondrial genome of Podospora anserina race s has been mapped and sequenced (1 kb = 10 3 base-pairs). This DNA region is continuous with the sequence for the ND4L and ND5 gene complex in the accompanying paper. We show that this sequence contains the gene for cytochrome oxidase subunit II (COII). This gene is 4 kb in length and is interrupted by a subgroup IB intron (1267 base-pairs (bp) in length) and a subgroup IA intron (1992 bp in length). This group IA intron has a long open reading frame (ORF; 472 amino acid residues) discontinuous with the upstream exon sequence. A putative alternative splice site is present, which brings the ORF into phase with the 5′ exon sequence. The 5′- and 3′-flanking regions of the COII gene contain G + C-rich palindromic sequences that resemble similar sequences flanking many Neurospora crassa mitochondrial genes.

Structure and evolution of primate cytochrome c oxidase subunit II gene.

The sequence of cytochrome oxidase subunit II (COII) mRNA from the cynomolgus macaque has been determined. Availability of the sequence from a non-human primate has allowed examination of the evolution of the COII gene and protein along the primate lineage. Comparison with existing protein and DNA sequences, combined with estimates of divergence derived from calculations designed to compensate for multiple mutation and reversion events, indicates that although the rate of fixation of nucleotide substitutions at silent sites is somewhat lower in primates than non-primates, the rate of fixation at replacement sites is 4-5-fold higher. The data also suggest that the rate of divergence at replacement sites along the primate lineage has not been uniform, but has decreased 2-2.5-fold since the higher primate branch point, in the absence of a comparable change in the rate substitution at silent sites. Both primate mRNAs differ from their non-primate homologues in having 3'-untranslated regions of 20-25 nucleotides. Examination of the monkey and human untranslated sequences suggests that these regions have evolved by duplication events occurring in both cases within 2-3 nucleotides following the translational stop codon. The primate mRNAs are also exceptional in that both can form stable stem and loop structures immediately preceding the postulated duplication site that may have played a role in facilitating the mutational events involved. Comparison of the human and monkey protein sequences has revealed regions conserved in primates that are significantly more hydrophobic than their non-primate counterparts. The possible effects of these alterations on the interaction between COII and cytochrome c are discussed.

Cytochrome Oxidase Subunit II Gene from Carrot Contains an Intron

Introns in the cytochrome oxidase subunit II (COXII) gene of plant mitochondrial DNA (mtDNA) have been observed only in monocots. The COXII genes in dicots investigated to date do not contain introns. This is the first report of an intron in the COXII gene of a dicot. The presence of an intron in the carrot COXII intron was verified by restriction mapping and hybridization using specific maize and wheat COXII probes. Regions of the carrot COXII intron are homologous to the maize COXII intron and homologous to the wheat COXII intron-insert as demonstrated by hybridization. Homology of these regions was confirmed by sequencing portions of the gene. A comparison of the restriction map of the carrot COXII gene with the restriction maps of the COXII genes from pea, Oenothera, maize, wheat, and rice revealed that the carrot map coincides with the rice restriction map.