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1.
Suga H Koyanagi M Hoshiyama D Ono K Iwabe N Kuma K Miyata T 《Journal of molecular evolution》1999,48(6):646-653
To know whether genes involved in cell–cell communication typical of multicellular animals dramatically increased in concert
with the Cambrian explosion, the rapid evolutionary burst in the major groups of animals, and whether these genes exist in
the sponge lacking cell cohesiveness and coordination typical of eumetazoans, we have carried out cloning of the G-protein
α subunit (Gα) and the protein tyrosine kinase (PTK) cDNAs from Ephydatia fluviatilis (freshwater sponge) and Hydra magnipapillata strain 105 (hydra). We obtained 13 Gα and 20 PTK cDNAs. Generally animal gene families diverged first by gene duplication
(subtype duplication) that gave rise to diverse subtypes with different primary functions, followed by further gene duplication
in the same subtype (isoform duplication) that gave rise to isoform genes with virtually identical function. Phylogenetic
trees of Gα and PTK families including cDNAs from sponge and hydra revealed that most of the present-day subtypes had been
established in the very early evolution of animals before the parazoan–eumetazoan split, the earliest branching among the
extant animal phyla, by extensive subtype duplication: for PTK and Gα families, 23 and 9 subtype duplications were observed
in the early stage before the parazoan–eumetazoan split, respectively, and after that split, only 2 and 1 subtype duplications
were found, respectively. After the separation from arthropods, vertebrates underwent frequent isoform duplications before
the fish–tetrapod split. Furthermore, rapid amino acid changes appear to have occurred in concert with the extensive subtype
duplication and isoform duplication. Thus the pattern of gene diversification during animal evolution might be characterized
by bursts of gene duplication interrupted by considerably long periods of silence, instead of proceeding gradually, and there
might be no direct link between the Cambrian explosion and the extensive gene duplication that generated diverse functions
(subtypes) of these families.
Received: 4 November 1998 / Accepted: 17 November 1998 相似文献
2.
3.
Protein tyrosine phosphatases (PTPs) regulate various physiological events in animal cells. They comprise a diverse family
which are classified into two categories, receptor type and nonreceptor type. From the domain organization and phylogenetic
tree, we have classified known PTPs into 17 subtypes (9 receptor-type and 8 nonreceptor-type PTPs) which are characterized
by different organization of functional domain and independent cluster in tree. The receptor type PTPs are thought to be implicated
in cell–cell adhesion by association of cell adhesion molecules. Since sponges are the most primitive multicellular animals
and are thought to be lacking cell cohesiveness and coordination typical of eumetazoans, cloning and sequencing of PTP cDNAs
of Ephydatia fluviatilis (freshwater sponge) have been conducted by RT-PCR to determine whether or not sponges have PTP genes in their genomes. We
have isolated nine PTPs, of which five are possibly receptor type. A phylogenetic tree including the sponge PTPs revealed
that most of the gene duplications that gave rise to the 17 subtypes had been completed in the very early evolution of animals
before the parazoan–eumetazoan split, the earliest branching among extant animal phyla. The family tree also revealed the
rapid evolutionary rate of PTP subtypes in the early stage of animal evolution.
Received: 22 October 1998 / Accepted: 27 November 1998 相似文献
4.
Cristian Cañestro Ricard Albalat Lars Hjelmqvist Laura Godoy Hans Jörnvall Roser Gonzàlez-Duarte 《Journal of molecular evolution》2002,54(1):81-89
The alcohol dehydrogenase (ADH) family has evolved into at least eight ADH classes during vertebrate evolution. We have characterized
three prevertebrate forms of the parent enzyme of this family, including one from an urochordate (Ciona intestinalis) and two from cephalochordates (Branchiostoma floridae and Branchiostoma lanceolatum). An evolutionary analysis of the family was performed gathering data from protein and gene structures, exon–intron distribution,
and functional features through chordate lines. Our data strongly support that the ADH family expansion occurred 500 million
years ago, after the cephalochordate/vertebrate split, probably in the gnathostome subphylum line of the vertebrates. Evolutionary
rates differ between the ancestral, ADH3 (glutathione-dependent formaldehyde dehydrogenase), and the emerging forms, including
the classical alcohol dehydrogenase, ADH1, which has an evolutionary rate 3.6-fold that of the ADH3 form. Phylogenetic analysis
and chromosomal mapping of the vertebrate Adh gene cluster suggest that family expansion took place by tandem duplications, probably concurrent with the extensive isoform
burst observed before the fish/tetrapode split, rather than through the large-scale genome duplications also postulated in
early vertebrate evolution. The absence of multifunctionality in lower chordate ADHs and the structures compared argue in
favor of the acquisition of new functions in vertebrate ADH classes. Finally, comparison between B. floridae and B. lanceolatum Adhs provides the first estimate for a cephalochordate speciation, 190 million years ago, probably concomitant with the beginning
of the drifting of major land masses from the Pangea.
Received: 10 April 2001 / Accepted: 23 May 2001 相似文献
5.
Edward L. Braun Seogchan Kang Mary Anne Nelson Donald O. Natvig 《Journal of molecular evolution》1998,47(5):531-543
Annexin homologues have been found in animals, plants, and distinct protist lineages. We report the identification of the
first fungal annexin, encoded by the anx14 gene of the filamentous ascomycete Neurospora crassa. Annexins have a complex evolutionary history and exhibit a large number of gene duplications and gene losses in various taxa,
including the complete loss of annexin sequences from another ascomycete, the budding yeast Saccharomyces cerevisiae. Surprisingly, the N. crassa annexin homologue is most closely related to the annexin homologue of the slime mold Dictyostelium discoideum, suggesting a phylogenetic link between cellular slime molds and true fungi. Both of these annexin homologues are closely
related to the family of annexin homologues present in animals, an observation consistent with the existence of the animal–fungal
clade. These data further suggest that the gene duplications that generated the family of annexin sequences present in animals,
fungi, and slime molds began prior to the divergence of these taxa.
Received: 10 December 1997 / Accepted: 17 April 1998 相似文献
6.
We have compared all available deduced protein sequences of the ErbB family of receptors and their ligands. Analysis of the
aligned sequences of the receptors indicates that there are some differences in the receptors that are specific to invertebrates.
In addition, comparison of the vertebrate ErbB receptors suggest that a gene duplication event generated two ancestral receptors,
the ErbB3/ErbB4 precursor and the ErbB1/ErbB2 precursor. Subsequent gene duplications of these precursors generated the four
receptors present in mammals. Analysis of the sequences for the known ligands of the ErbB receptors suggests that the vertebrate
ligands segregate into the ErbB1 ligands and the ErbB3/ErbB4 ligands, paralleling the evolution of the receptors; however,
it is difficult to ascertain any correlation between the invertebrate and the vertebrate ligands. Even though ErbB3 is kinase-impaired,
there is significant conservation of the kinase domain within the vertebrate lineage (human, rat, and F. rubripes), suggesting some function for this domain other than kinase activity, such as mediating protein–protein interactions that
are involved in receptor dimerization and/or activation of the kinase domain of the heterodimerization partner. To date, no
ligand for ErbB2 has been identified, and comparison of the extracellular domains of ErbB2 reveals two regions that are not
conserved across the mammalian species. These two regions of divergence align with sequences in ErbB1 that have been shown
to be proximal to the amino-terminus and to the carboxyl-terminal region, respectively, of bound EGF. Further, one of these
regions contains an insertion, relative to the other members of the mammalian ErbB family, which might affect the ligand binding
site and provide a structural basis for this receptor's apparent inability to bind ligand independently.
Received: 8 September 1999 / Accepted: 17 January 2000 相似文献
7.
Evolution of the Integrin α and β Protein Families 总被引:4,自引:0,他引:4
Hughes AL 《Journal of molecular evolution》2001,52(1):63-72
A phylogenetic analysis of vertebrate and invertebrate α integrins supported the hypothesis that two major families of vertebrate
α integrins originated prior to the divergence of deuterostomes and protostomes. These two families include, respectively,
the αPS1 and αPS2 integrins of Drosophila melanogaster, and each family has duplicated repeatedly in vertebrates but not in Drosophila. In contrast, a third family (including αPS3) has duplicated in Drosophila but is absent from vertebrates. Vertebrate αPS1 and αPS2 family members are found on human chromosomes 2, 12, and 17. Linkage
of these family members may have been conserved since prior to the origin of vertebrates, and the two genes duplicated simultaneously.
A phylogenetic analysis of β integrins did not clearly resolve whether vertebrate β integrin genes duplicated prior to the
origin of vertebrates, although it suggested that at least the gene encoding vertebrate β4 may have done so. In general, the
phylogeny of neither α nor β integrins showed a close correspondence with patterns of α–β heterodimer formation or other functional
characteristics. One major exception to this trend involved αL, αM, αX, and αD, a monophyletic group of immune cell-expressed
α integrins, which share a number of common functional characteristics and have evolved in coordinated fashion with their
β integrin partners.
Received: 22 June 2000 / Accepted: 11 September 2000 相似文献
8.
Naruo Nikoh Naoyuki Iwabe Kei-ichi Kuma Mutsuhito Ohno Tsutomu Sugiyama Yoko Watanabe Kinya Yasui Zhang Shi-cui Katsuji Hori Yoshiro Shimura Takashi Miyata 《Journal of molecular evolution》1997,45(1):97-106
Previously we suggested that four proteins including aldolase and triose phosphate isomerase (TPI) evolved with approximately
constant rates over long periods covering the whole animal phyla. The constant rates of aldolase and TPI evolution were reexamined
based on three different models for estimating evolutionary distances. It was shown that the evolutionary rates remain essentially
unchanged in comparisons not only between different classes of vertebrates but also between vertebrates and arthropods and
even between animals and plants, irrespective of the models used. Thus these enzymes might be useful molecular clocks for
inferring divergence times of animal phyla. To know the divergence time of Parazoa and Eumetazoa and that of Cephalochordata
and Vertebrata, the aldolase cDNAs from Ephydatia fluviatilis, a freshwater sponge, and the TPI cDNAs from Ephydatia fluviatilis and Branchiostoma belcheri, an amphioxus, have been cloned and sequenced. Comparisons of the deduced amino acid sequences of aldolase and TPI from the
freshwater sponge with known sequences revealed that the Parazoa–Eumetazoa split occurred about 940 million years ago (Ma)
as determined by the average of two proteins and three models. Similarly, the aldolase and TPI clocks suggest that vertebrates
and amphioxus last shared a common ancestor around 700 Ma and they possibly diverged shortly after the divergence of deuterostomes
and protostomes. 相似文献
9.
Peter E.M. Gibbs Werner F. Witke Achilles Dugaiczyk 《Journal of molecular evolution》1998,46(5):552-561
The serum albumin gene family is composed of four members that have arisen by a series of duplications from a common ancestor.
From sequence differences between members of the gene family, we infer that a gene duplication some 580 Myr ago gave rise
to the vitamin D–binding protein (DBP) gene and a second lineage, which reduplicated about 295 Myr ago to give the albumin
(ALB) gene and a common precursor to α-fetoprotein (AFP) and α-albumin (ALF). This precursor itself duplicated about 250 Myr
ago, giving rise to the youngest family members, AFP and ALF. It should be possible to correlate these dates with the phylogenetic
distribution of members of the gene family among different species. All four genes are found in mammals, but AFP and ALF are
not found in amphibia, which diverged from reptiles about 360 Myr ago, before the divergence of the AFP-ALF progenitor from
albumin.
Although individual family members display an approximate clock-like evolution, there are significant deviations—the rates
of divergence for AFP differ by a factor of 7, the rates for ALB differ by a factor of 2.1. Since the progenitor of this gene
family itself arose by triplication of a smaller gene, the rates of evolution of individual domains were also calculated and
were shown to vary within and between family members. The great variation in the rates of the molecular clock raises questions
concerning whether it can be used to infer evolutionary time from contemporary sequence differences.
Received: 28 February 1995 / Accepted: 6 October 1997 相似文献
10.
The extracellular hemoglobins of cladocerans derive from the aggregation of 12 two-domain globin subunits that are apparently
encoded by four genes. This study establishes that at least some of these genes occur as a tandem array in both Daphnia magna and Daphnia exilis. The genes share a uniform structure; a bridge intron separates two globin domains which each include three exons and two
introns. Introns are small, averaging just 77 bp, but a longer sequence (2.2–3.2 kb) separates adjacent globin genes. A survey
of structural diversity in globin genes from other daphniids revealed three independent cases of intron loss, but exon lengths
were identical, excepting a 3-bp insertion in exon 5 of Simocephalus. Heterogeneity in the extent of nucleotide divergence was marked among exons, largely as a result of the pronounced diversification
of the terminal exon. This variation reflected, in part, varying exposure to concerted evolution. Conversion events were frequent
in exons 1–4 but were absent from exons 5 and 6. Because of this difference, the results of phylogenetic analyses were strongly
affected by the sequences employed in this construction. Phylogenies based on total nucleotide divergence in exons 1–4 revealed
affinities among all genes isolated from a single species, reflecting the impact of gene conversion events. In contrast, phylogenies
based on total nucleotide divergence in exons 5 and 6 revealed affinities among orthologous genes from different taxa.
Received: 8 March 1999 / Accepted: 14 July 1999 相似文献
11.
Diversity, Distribution, and Ancient Taxonomic Relationships Within the TIR and Non-TIR NBS-LRR Resistance Gene Subfamilies 总被引:1,自引:0,他引:1
Cannon SB Zhu H Baumgarten AM Spangler R May G Cook DR Young ND 《Journal of molecular evolution》2002,54(4):548-562
Phylogenetic relationships among the NBS-LRR (nucleotide binding site–leucine-rich repeat) resistance gene homologues (RGHs)
from 30 genera and nine families were evaluated relative to phylogenies for these taxa. More than 800 NBS-LRR RGHs were analyzed,
primarily from Fabaceae, Brassicaceae, Poaceae, and Solanaceae species, but also from representatives of other angiosperm
and gymnosperm families. Parsimony, maximum likelihood, and distance methods were used to classify these RGHs relative to
previously observed gene subfamilies as well as within more closely related sequence clades. Grouping sequences using a distance
cutoff of 250 PAM units (point accepted mutations per 100 residues) identified at least five ancient sequence clades with
representatives from several plant families: the previously observed TIR gene subfamily and a minimum of four deep splits
within the non-TIR gene subfamily. The deep splits in the non-TIR subfamily are also reflected in comparisons of amino acid
substitution rates in various species and in ratios of nonsynonymous-to-synonymous nucleotide substitution rates (K
A/K
S values) in Arabidopsis thaliana. Lower K
A/K
S values in the TIR than the non-TIR sequences suggest greater functional constraints in the TIR subfamily. At least three
of the five identified ancient clades appear to predate the angiosperm–gymnosperm radiation. Monocot sequences are absent
from the TIR subfamily, as observed in previous studies. In both subfamilies, clades with sequences separated by approximately
150 PAM units are family but not genus specific, providing a rough measure of minimum dates for the first diversification
event within these clades. Within any one clade, particular taxa may be dramatically over- or underrepresented, suggesting
preferential expansions or losses of certain RGH types within particular taxa and suggesting that no one species will provide
models for all major sequence types in other taxa.
Received: 13 June 2001 / Accepted: 22 October 2001 相似文献
12.
In this paper we have analyzed 49 vertebrate gene families that were generated in the early stage of vertebrates and/or shortly
before the origin of vertebrates, each of which consists of three or four member genes. We have dated the first (T1) and second (T2) gene duplications of 26 gene families with 3 member genes. The means of T1 (594 mya) and T2 (488 mya) are largely consistent to a well-cited version of two-round (2R) genome duplication theory. Moreover, in most cases,
the time interval between two successive gene duplications is large enough that the fate of duplicate genes generated by the
first gene duplication was likely to be determined before the second one took place. However, the phylogenetic pattern of
23 gene families with 4 members is complicated; only 5 of them are predicted by 2R model, but 11 families require an additional
gene (or genome) duplication. For the rest (7 families), at least one gene duplication event had occurred before the divergence
between vertebrate and Drosophila, indicating a possible misleading of the 4:1 rule (member gene ratio between vertebrates and invertebrates). Our results show
that Ohno's 2R conjecture is valid as a working hypothesis for providing a most parsimonious explanation. Although for some
gene families, additional gene duplication is needed, the credibility of the third genome duplication (3R) remains to be investigated.
Received: 13 December 1999 / Accepted: 7 April 2000 相似文献
13.
Satoru Kanai Reiko Kikuno Hiroyuki Toh Haruko Ryo Takeshi Todo 《Journal of molecular evolution》1997,45(5):535-548
The photolyase–blue-light photoreceptor family is composed of cyclobutane pyrimidine dimer (CPD) photolyases, (6-4) photolyases,
and blue-light photoreceptors. CPD photolyase and (6-4) photolyase are involved in photoreactivation for CPD and (6-4) photoproducts,
respectively. CPD photolyase is classified into two subclasses, class I and II, based on amino acid sequence similarity. Blue-light
photoreceptors are essential light detectors for the early development of plants. The amino acid sequence of the receptor
is similar to those of the photolyases, although the receptor does not show the activity of photoreactivation. To investigate
the functional divergence of the family, the amino acid sequences of the proteins were aligned. The alignment suggested that
the recognition mechanisms of the cofactors and the substrate of class I CPD photolyases (class I photolyases) are different
from those of class II CPD photolyases (class II photolyases). We reconstructed the phylogenetic trees based on the alignment
by the NJ method and the ML method. The phylogenetic analysis suggested that the ancestral gene of the family had encoded
CPD photolyase and that the gene duplication of the ancestral proteins had occurred at least eight times before the divergence
between eubacteria and eukaryotes.
Received: 23 October 1996 / Accepted: 1 April 1997 相似文献
14.
To understand the question of whether divergence of eukaryotic genes by gene duplications and domain shufflings proceeded gradually or intermittently during evolution, we have cloned and sequenced Giardia lamblia cDNAs encoding kinesins and kinesin-related proteins and have obtained 13 kinesin-related cDNAs, some of which are likely homologs of vertebrate kinesins involved in vesicle transfer to ER, Golgi, and plasma membrane. A phylogenetic tree of the kinesin family revealed that most gene duplications that gave rise to different kinesin subfamilies with distinct functions have been completed before the earliest divergence of extant eukaryotes. This suggests that the complex endomembrane system has arisen very early in eukaryotic evolution, and the diminutive ER and Golgi apparatus recognized in the giardial cells, together with the absence of mitochondria, might be characters acquired secondarily during the evolution of parasitism. To understand the divergence pattern of the kinesin family in the lineage leading to vertebrates, seven more Unc104-related cDNAs have been cloned from sponge, amphioxus, hagfish, and lamprey. The divergence pattern of the animal Unc104/KIF1 subfamily is characterized by two active periods in gene duplication interrupted by a considerably long period of silence, instead of proceeding gradually: animals underwent extensive gene duplications before the parazoan-eumetazoan split. In the early evolution of vertebrates around the cyclostome-gnathostome split, further gene duplications occurred, by which a variety of genes with similar structures over the entire regions were generated. This pattern of divergence is similar to those of animal genes involved in cell-cell communication and developmental control. 相似文献
15.
A full-length cytochrome b pseudogene was found in rodents; it has apparently been translocated from a mitochondrion to the nuclear genome in the subfamily
Arvicolinae. The pseudogene (ψcytb) differed from its mitochondrial counterpart at 201 of 1143 sites (17.6%) and by four indels. Cumulative evidence suggests
that the pseudogene has been translocated to the nucleus. Phylogenetic reconstruction indicates that the pseudogene arose
before the diversification of M. arvalis/M. rossiaemeridionalis from M. oeconomus, but after the divergence of the peromyscine/sigmodontine/arvicoline clades some ∼10 MYA. Published rates of divergence between
mitochondrial genes and their nuclear pseudogenes suggest that the translocation of this mitochondrial gene to the nuclear
genome occurred some 6 MYA, in agreement with the phylogenetic evidence.
Received: 16 January 1998 / Accepted: 18 July 1998 相似文献
16.
Of Worms and Men: An Evolutionary Perspective on the Fibroblast Growth Factor (FGF) and FGF Receptor Families 总被引:6,自引:0,他引:6
François Coulier Pierre Pontarotti Régine Roubin Helge Hartung Mitchell Goldfarb Daniel Birnbaum 《Journal of molecular evolution》1997,44(1):43-56
FGFs (fibroblast growth factors) play major roles in a number of developmental processes. Recent studies of several human
disorders, and concurrent analysis of gene knock-out and properties of the corresponding recombinant proteins have shown that
FGFs and their receptors are prominently involved in the development of the skeletal system in mammals. We have compared the
sequences of the nine known mammalian FGFs, FGFs from other vertebrates, and three additional sequences that we extracted
from existing databases: two human FGF sequences that we tentatively designated FGF10 and FGF11, and an FGF sequence from
C?norhabditis elegans. Similarly, we have compared the sequences of the four FGF receptor paralogs found in chordates with four non-chordate FGF
receptors, including one recently identified in C. elegans. The comparison of FGF and FGF receptor sequences in vertebrates and nonvertebrates shows that the FGF and FGF receptor families
have evolved through phases of gene duplications, one of which may have coincided with the emergence of vertebrates, in relation
with their new system of body scaffold.
Received: 6 April 1996 / Accepted: 5 July 1996 相似文献
17.
The phylogenetic position of hagfishes in vertebrate evolution is currently controversial. The 18S and 28S rRNA trees support
the monophyly of hagfishes and lampreys. In contrast, the mitochondrial DNAs suggest the close association of lampreys and
gnathostomes. To clarify this controversial issue, we have conducted cloning and sequencing of the four nuclear DNA–coded
single-copy genes encoding the triose phosphate isomerase, calreticulin, and the largest subunit of RNA polymerase II and
III. Based on these proteins, together with the Mn superoxide dismutase for which hagfish and lamprey sequences are available
in database, phylogenetic trees have been inferred by the maximum likelihood (ML) method of protein phylogeny. It was shown
that all the five proteins prefer the monophyletic tree of cyclostomes, and the total log-likelihood of the five proteins
significantly supports the cyclostome monophyly at the level of ±1 SE. The ML trees of aldolase family comprising three nonallelic
isoforms and the complement component group comprising C3, C4, and C5, both of which diverged during vertebrate evolution
by gene duplications, also suggest the cyclostome monophyly.
Received: 28 April 1999 / Accepted: 30 June 1999 相似文献
18.
Calpains, the Ca2+-dependent intracellular proteinases, are involved in the regulation of distinct cellular pathways including signal transduction
and processing, cytoskeleton dynamics, and muscle homeostasis. To investigate the evolutionary origin of diverse calpain subfamilies,
a phylogenetic study was carried out. The topology of the calpain phylogenetic tree has shown that some of the gene duplications
occurred before the divergence of the protostome and deuterostome lineages. Other gene doublings, leading to vertebrate-specific
calpain forms, took place during early chordate evolution and coincided with genome duplications as disclosed by the localization
of calpain genes to paralogous chromosome regions in the human genome. On the basis of the phylogenetic tree, the time of
gene duplications, and the localization of calpain genes, we propose a model of tandem and chromosome duplications for the
evolution of vertebrate-specific calpain forms. The data presented here are consistent with scenarios proposed for the evolution
of other multigene families.
Received: 17 November 1998 / Accepted: 30 April 1999 相似文献
19.
The pairs of nitrogen fixation genes nifDK and nifEN encode for the α and β subunits of nitrogenase and for the two subunits of the NifNE protein complex, involved in the biosynthesis
of the FeMo cofactor, respectively. Comparative analysis of the amino acid sequences of the four NifD, NifK, NifE, and NifN
in several archaeal and bacterial diazotrophs showed extensive sequence similarity between them, suggesting that their encoding
genes constitute a novel paralogous gene family. We propose a two-step model to reconstruct the possible evolutionary history
of the four genes. Accordingly, an ancestor gene gave rise, by an in-tandem paralogous duplication event followed by divergence,
to an ancestral bicistronic operon; the latter, in turn, underwent a paralogous operon duplication event followed by evolutionary
divergence leading to the ancestors of the present-day nifDK and nifEN operons. Both these paralogous duplication events very likely predated the appearance of the last universal common ancestor.
The possible role of the ancestral gene and operon in nitrogen fixation is also discussed.
Received: 21 June 1999 / Accepted: 1 March 2000 相似文献
20.
The complete nucleotide sequence of the mitochondrial genome was determined for a conger eel, Conger myriaster (Elopomorpha: Anguilliformes), using a PCR-based approach that employs a long PCR technique and many fish-versatile primers.
Although the genome [18,705 base pairs (bp)] contained the same set of 37 mitochondrial genes [two ribosomal RNA (rRNA), 22
transfer RNA (tRNA), and 13 protein-coding genes] as found in other vertebrates, the gene order differed from that recorded
for any other vertebrates. In typical vertebrates, the ND6, tRNAGlu, and tRNAPro genes are located between the ND5 gene and the control region, whereas the former three genes, in C. myriaster, have been translocated to a position between the control region and the tRNAPhe gene that are contiguously located at the 5′ end of the 12S rRNA gene in typical vertebrates. This gene order is similar
to the recently reported gene order in four lineages of birds in that the latter lack the ND6, tRNAGlu, and tRNAPro genes between the ND5 gene and the control region; however, the relative position of the tRNAPro to the ND6–tRNAGlu genes in C. myriaster was different from that in the four birds, which presumably resulted from different patterns of tandem duplication of gene
regions followed by gene deletions in two distantly related groups of organisms. Sequencing of the ND5–cyt b region in 11 other anguilliform species, representing 11 families, plus one outgroup species, revealed that the same gene
order as C. myriaster was shared by another 4 families, belonging to the suborder Congroidei. Although the novel gene orders of four lineages of
birds were indicated to have multiple independent origins, phylogenetic analyses using nucleotide sequences from the mitochondrial
12S rRNA and cyt b genes suggested that the novel gene orders of the five anguilliform families had originated in a single ancestral species.
Received: 13 July 2000 / Accepted: 30 November 2000 相似文献