共查询到20条相似文献,搜索用时 156 毫秒
1.
Maria Pilar Fernández Neal G. Copeland Debra J. Gilbert Nancy A. Jenkins Reginald O. Morgan 《Mammalian genome》1998,9(1):8-14
Mouse annexin VIII cDNA was characterized by DNA sequencing of expressed sequence tag clones, molecular systematic analysis,
and genetic linkage mapping to investigate its evolutionary origin. Its subfamily identity, divergence pattern, and nucleotide
substitution rate were established by comparison with other annexin cDNA and deduced protein sequences. The known phylogenetic
association of annexin VIII in an evolutionary clade with annexins XI, IV, V, and VIa identified these close homologs as potential
progenitors or duplication products. Cladistic analysis confirmed the base position of annexin XI and its relationship to
annexin IV as a direct duplication product. Although annexin VIII also derived from annexin XI, the evolutionary branching
order, gene separation times, and mapping results indicated that it was probably a subsequent duplication product of annexin
IV about 300 million years ago. Dates were calibrated against the assumed separation time of 75 Mya for rodents from other
mammals, divergence rates were based on comparisons of all available annexin species, and relative rate tests implied individually
stable gene clocks for most annexins. Linkage mapping of mouse Anx8 to the centromeric region of Chromosome (Chr) 14 placed it in a more distal homology group from previously mapped Anx7 and Anx11. Despite their synteny, the combined proximity and segregation of these three annexins diminished the likelihood that they
were mutual gene duplication products.
Received: 25 May 1997 / Accepted: 13 September 1997 相似文献
2.
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
3.
《Gene》1998,207(1):43-51
Mouse annexin III cDNA was characterized from I.M.A.G.E. Consortium (LLNL) expressed sequence tag clones by molecular sequencing, chromosomal mapping and systematic analysis. cDNA sequences extended the known 5′ and 3′ untranslated regions and confirmed the location of intron 7 with respect to the human gene. The Anx3 locus mapped to the middle of mouse chromosome 5 between Areg and Fgf5. Protein-coding regions were compared with homologous annexins to establish subfamily identity, structural conservation and divergence pattern. Annexin III exhibited low functional constraint against structural change and weak phylogenetic association with known annexins. The rapid, constant divergence of human and rodent annexins III from each other and from other annexin subfamilies was used to estimate gene separation times. Phylogenetic, phenetic and structural data suggested a possible direct or indirect separation of annexin III from XI approximately 317 million years ago. 相似文献
4.
Olivier Verneau François Catzeflis Anthony V. Furano 《Journal of molecular evolution》1997,45(4):424-436
We determined ∼215 bp of DNA sequence from the 3′-untranslated region (UTR) of 240 cloned L1 (LINE-1) elements isolated from
22 species of Rattus sensu lato and Rattus sensu stricto murine rodents. The sequences were sorted into different L1 subfamilies, and oligonucleotides cognate to them
were hybridized to genomic DNA of various taxa. From the distribution of the L1 subfamilies in the various species, we inferred
the partial phylogeny of Rattus sensu lato. The four Maxomys species comprise a well-defined clade separate from a monophyletic cluster that contains the two Leopoldamys and four Niviventer species. The Niviventer/Leopoldamys clade, in turn, shares a node with the clade that contains Berylmys, Sundamys, Bandicota, and Rattus sensu stricto. The evolutionary relationships that we deduced agree with and significantly extend the phylogeny of Rattus sensu lato established by other molecular criteria. Furthermore, the L1 amplification events scored here produced a unique
phylogenetic tree, that is, in no case did a character (a given L1 amplification event) appear on more than one branch. The
lack of homoplasy found in this study supports the robustness of L1 amplification events as phylogenetic markers for the study
of mammalian evolution.
Received: 8 November 1996 / Accepted: 11 April 1997 相似文献
5.
Hofmann A Ruvinov S Hess S Schantz R Delmer DP Wlodawer A 《Protein science : a publication of the Protein Society》2002,11(8):2033-2040
The oligomeric state in solution of four plant annexins, namely Anx23(Ca38), Anx24(Ca32), Anx(Gh1), and Anx(Gh2), was characterized by sedimentation equilibrium analysis and gel filtration. All proteins were expressed and purified as amino-terminal His(n) fusions. Sequencing of the Anx(Gh1) construct revealed distinct differences with the published sequence. Sedimentation equilibrium analysis of Anx23(Ca38), Anx24(Ca32), and Anx(Gh1) suggests monomer-trimer equilibria for each protein with association constants in the range of 0.9 x 10(10)-1.7 x 10(11) M(-2). All four proteins were subjected to analytical gel filtration under different buffer conditions. Observations from this experiment series agree quantitatively with the ultracentrifugation results, and strongly suggest calcium independence of the annexin oligomerization behavior; moreover, binding of calcium ions to the proteins seems to require disassembly of the oligomers. Anx(Gh2) showed a different elution profile than the other plant annexins; while having only a very small trimer content, this annexin seems to exist in a monomer-dimer equilibrium in solution. 相似文献
6.
Yuji Inagaki Yasuko Hayashi-Ishimaru Megumi Ehara Ikuo Igarashi Takeshi Ohama 《Journal of molecular evolution》1997,45(3):295-300
The chloroplasts of euglenophytes and dinoflagellates have been suggested to be the vestiges of endosymbiotic algae acquired
during the process of evolution. However, the evolutionary positions of these organisms are still inconclusive, and they have
been tentatively classified as both algae and protozoa. A representative gene of the mitochondrial genome, cytochrome oxidase
subunit I (coxI), was chosen and sequenced to clarify the phylogenetic positions of four dinoflagellates, two euglenophytes and one apicomplexan
protist. This is the first report of mitochondrial DNA sequences for dinoflagellates and euglenophytes. Our COXI tree shows clearly that dinoflagellates are closely linked to apicomplexan parasites but not with algae. Euglenophytes and
algae appear to be only remotely related, with euglenophytes sharing a possible evolutionary link with kinetoplastids. The
COXI tree is in general agreement with the tree based on the nuclear encoded small subunit of ribosomal RNA (SSU rRNA) genes,
but conflicts with that based on plastid genes. These results support the interpretation that chloroplasts present in euglenophytes
and dinoflagellates were captured from algae through endosymbioses, while their mitochondria were inherited from the host
cell. We suggest that dinoflagellates and euglenophytes were originally heterotrophic protists and that their chloroplasts
are remnants of endosymbiotic algae.
Received: 24 March 1997 / Accepted: 21 April 1997 相似文献
7.
Andreas Hofmann Deborah P Delmer Alexander Wlodawer 《European journal of biochemistry》2003,270(12):2557-2564
The three-dimensional crystal structure of recombinant annexin Gh1 from Gossypium hirsutum (cotton fibre) has been determined and refined to the final R-factor of 0.219 at the resolution of 2.1 A. This plant annexin consists of the typical 'annexin fold' and is similar to the previously solved bell pepper annexin Anx24(Ca32), but significant differences are seen when compared to the structure of nonplant annexins. A comparison with the structure of the mammalian annexin AnxA5 indicates that canonical calcium binding is geometrically possible within the membrane loops in domains I and II of Anx(Gh1) in their present conformation. All plant annexins possess a conserved tryptophan residue in the AB loop of the first domain; this residue was found to adopt both a loop-in and a loop-out conformation in the bell pepper annexin Anx24(Ca32). In Anx(Gh1), the conserved tryptophan residue is in a surface-exposed position, half way between both conformations observed in Anx24(Ca32). The present structure reveals an unusual sulfur cluster formed by two cysteines and a methionine in domains II and III, respectively. While both cysteines adopt the reduced thiolate forms and are separated by a distance of about 5.5 A, the sulfur atom of the methionine residue is in their close vicinity and apparently interacts with both cysteine sulfur atoms. While the cysteine residues are conserved in at least five plant annexins and in several mammalian members of the annexin family of proteins, the methionine residue is conserved only in three plant proteins. Several of these annexins carrying the conserved residues have been implicated in oxidative stress response. We therefore hypothesize that the cysteine motif found in the present structure, or possibly even the entire sulfur cluster, forms the molecular basis for annexin function in oxidative stress response. 相似文献
8.
Javier García-Planells Nuria Paricio Jonathan B. Clark Rosa de Frutos Margaret G. Kidwell 《Journal of molecular evolution》1998,47(3):282-291
A phylogenetic analysis of P transposable elements in the Drosophila obscura species group is described. Multiple P sequences from each of 10 species were obtained using PCR primers that flank a conserved region of exon 2 of the transposase
gene. In general, the P element phylogeny is congruent with the species phylogeny, indicating that the dominant mode of transmission has been vertical,
from generation to generation. One manifestation of this is the distinction of P elements from the Old World obscura and subobscura subgroups from those of the New World affinis subgroup. However, the overall distribution of elements within the obscura species group is not congruent with the phylogenetic relationships of the species themselves. There are at least four distinct
subfamilies of P elements, which differ in sequence from each other by as much as 34%, and some individual species carry sequences belonging
to different subfamilies. P sequences from D. bifasciata are particularly interesting. These sequences belong to two subfamilies and both are distinct from all other P elements identified in this survey. Several mechanisms are postulated to be involved in determining phylogenetic relationships
among P elements in the obscura group. In addition to vertical transmission, these include retention of ancestral polymorphisms and horizontal transfer by
an unknown mating-independent mechanism. 相似文献
9.
Emmanuel Mertens Uri S. Ladror Jennifer A. Lee Anya Miretsky Andrea Morris Catherine Rozario Robert G. Kemp Miklós Müller 《Journal of molecular evolution》1998,47(6):739-750
The pyrophosphate-dependent phosphofructokinase (PPi-PFK) of the amitochondriate protist Trichomonas vaginalis has been purified. The enzyme is a homotetramer of about 50 kDa subunits and is not subject to allosteric regulation. The
protein was fragmented and a number of peptides were sequenced. Based on this information a PCR product was obtained from
T. vaginalis gDNA and used to isolate corresponding cDNA and gDNA clones. Southern analysis indicated the presence of five genes. One
open reading frame (ORF) was completely sequenced and for two others the 5′ half of the gene was determined. The sequences
were highly similar. The complete ORF corresponded to a polypeptide of about 46 kDa. All the peptide sequences obtained were
present in the derived sequences. The complete ORF was highly similar to that of other PFKs, primarily in its amino-terminal
half. The T. vaginalis enzyme was most similar to PPi-PFK of the mitochondriate heterolobosean, Naegleria fowleri. Most of the residues shown or assumed to be involved in substrate binding in other PPi-PFKs were conserved in the T. vaginalis enzyme. Direct comparison and phylogenetic reconstruction revealed a significant divergence among PPi-PFKs and related enzymes, which can be assigned to at least four distantly related groups, three of which contain enzymes
of protists. The separation of these groups is supported with a high percentage of bootstrap proportions. The short T. vaginalis PFK shares a most recent common ancestor with the enzyme from N. fowleri. This pair is clearly separated from a group comprising the long (>60-kDa) enzymes from Giardia lamblia, Entamoeba histolytica pfk2, the spirochaetes Borrelia burgdorferi and Trepomena pallidum, as well as the α- and β-subunits of plant PPi-PFKs. The third group (``X') containing protist sequences includes the glycosomal ATP-PFK of Trypanosoma brucei, E. histolytica pfk1, and a second sequence from B. burgdorferi. The fourth group (``Y') comprises cyanobacterial and high-G + C, Gram-positive eubacterial sequences. The well-studied PPi-PFK of Propionibacterium freudenreichii is highly divergent and cannot be assigned to any of these groups. These four groups are well separated from typical ATP-PFKs,
the phylogenetic analysis of which confirmed relationships established earlier. These findings indicate a complex history
of a key step of glycolysis in protists with several early gene duplications and possible horizontal gene transfers.
Received: 5 December 1997 / Accepted: 18 March 1998 相似文献
10.
11.
Evolutionary Relationship of the Ligand-Gated Ion Channels and the Avermectin-Sensitive,Glutamate-Gated Chloride Channels 总被引:4,自引:0,他引:4
Demetrios K. Vassilatis Keith O. Elliston Philip S. Paress Michel Hamelin Joseph P. Arena James M. Schaeffer Lex H.T. Van der Ploeg Doris F. Cully 《Journal of molecular evolution》1997,44(5):501-508
Two cDNAs, GluClα and GluClβ, encoding glutamate-gated chloride channel subunits that represent targets of the avermectin
class of antiparasitic compounds, have recently been cloned from Caenorhabditis elegans (Cully et al., Nature, 371, 707–711, 1994). Expression studies in Xenopus oocytes showed that GluClα and GluClβ have pharmacological profiles distinct from the glutamate-gated cation channels as
well as the γ-aminobutyric acid (GABA)- and glycine-gated chloride channels. Establishing the evolutionary relationship of
related proteins can clarify properties and lead to predictions about their structure and function. We have cloned and determined
the nucleotide sequence of the GluClα and GluClβ genes. In an attempt to understand the evolutionary relationship of these
channels with the members of the ligand-gated ion channel superfamily, we have performed gene structure comparisons and phylogenetic
analyses of their nucleotide and predicted amino acid sequences. Gene structure comparisons reveal the presence of several
intron positions that are not found in the ligand-gated ion channel superfamily, outlining their distinct evolutionary position.
Phylogenetic analyses indicate that GluClα and GluClβ form a monophyletic subbranch in the ligand-gated ion channel superfamily
and are related to vertebrate glycine channels/receptors. Glutamate-gated chloride channels, with electrophysiological properties
similar to GluClα and GluClβ, have been described in insects and crustaceans, suggesting that the glutamate-gated chloride
channel family may be conserved in other invertebrate species. The gene structure and phylogenetic analyses in combination
with the distinct pharmacological properties demonstrate that GluClα and GluClβ belong to a discrete ligand-gated ion channel
family that may represent genes orthologous to the vertebrate glycine channels.
Received: 30 September 1996 / Accepted: 15 November 1996 相似文献
12.
Sybille Kubis John Seymour Heslop-Harrison Thomas Schmidt 《Journal of molecular evolution》1997,44(3):310-320
Members of a highly abundant restriction satellite family have been isolated from the wild beet species Beta nana. The satellite DNA sequence is characterized by a conserved RsaI restriction site and is present in three of four sections of the genus Beta, namely Nanae, Corollinae, and Beta. It was not detected in species of the evolutionary old section Procumbentes, suggesting its amplification after separation of this section. Sequences of eight monomers were aligned revealing a size
variation from 209 to 233 bp and an AT content ranging from 56.5% to 60.5%. The similarity between monomers in B. nana varied from 77.7% to 92.2%. Diverged subfamilies were identified by sequence analysis and Southern hybridization. A comparative
study of this repetitive DNA element by fluorescent in situ hybridization and Southern analyses in three representative species
was performed showing a variable genomic organization and heterogeneous localizations along metaphase chromosomes both within
and between species. In B. nana the copy number of this satellite, with some 30,000 per haploid genome, is more than tenfold higher than in Beta lomatogona and up to 200 times higher than in Beta vulgaris, indicating different levels of sequence amplification during evolution in the genus Beta. In sugar beet (B. vulgaris), the large-scale organization of this tandem repeat was examined by pulsed-field gel electrophoresis. Southern hybridization
to genomic DNA digested with DraI demonstrated that satellite arrays are located in AT-rich regions and the tandem repeat is a useful probe for the detection
of genetic variation in closely related B. vulgaris cultivars, accessions, and subspecies.
Received: 24 May 1996 / Accepted: 13 September 1996 相似文献
13.
Alessandra Bonci Alessandra Chiesurin Patrizia Muscas Gian Maria Rossolini 《Journal of molecular evolution》1997,44(3):299-309
The structure of a Salmonella enterica serovar typhi gene located within the fim gene cluster and encoding a putative periplasmic chaperone-like protein involved in the assembly of type 1 pili was determined.
This gene, named fimC, has the ability to encode a 26-kDa polypeptide which is similar, at the sequence level, to the PapD periplasmic chaperonin
mediating the assembly of P pili of Escherichia coli, as well as to other periplasmic chaperone-like proteins involved in the biogenesis of pili or capsule-like structures of
various Gram-negative bacteria. A comprehensive search through the literature and sequence databases identified 31 (putative)
bacterial proteins that can be included in this protein family on the basis of sequence similarity. Results of a multiple
sequence comparison analysis showed that several residues, including most of those known to be critical in maintaining the
three-dimensional structure of PapD, are either conserved or conservatively substituted in all these proteins, suggesting
an overall similar folding for all of them. It was also evident that members of this family are clustered into different subfamilies
according to structural and phyletic data.
Received: 15 February 1996 / Accepted: 3 October 1996 相似文献
14.
Primary Structure and Phylogenetic Relationships of a Malate Dehydrogenase Gene from Giardia lamblia
The lactate and malate dehydrogenases comprise a complex protein superfamily with multiple enzyme homologues found in eubacteria,
archaebacteria, and eukaryotes. In this study we describe the sequence and phylogenetic relationships of a malate dehydrogenase
(MDH) gene from the amitochondriate diplomonad protist, Giardia lamblia. Parsimony, distance, and maximum-likelihood analyses of the MDH protein family solidly position G. lamblia MDH within a eukaryote cytosolic MDH clade, to the exclusion of chloroplast, mitochondrial, and peroxisomal homologues. Furthermore,
G. lamblia MDH is specifically related to a homologue from Trichomonas vaginalis. This MDH topology, together with published phylogenetic analyses of β-tubulin, chaperonin 60, valyl-tRNA synthetase, and
EF-1α, suggests a sister-group relationship between diplomonads and parabasalids. Since these amitochondriate lineages contain
genes encoding proteins which are characteristic of mitochondria and α-proteobacteria, their shared ancestry suggests that
mitochondrial properties were lost in the common ancestor of both groups.
Received: 14 September 1998 / Accepted: 29 December 1998 相似文献
15.
Molecular Data from the 16S rRNA Gene for the Phylogeny of Pectinidae (Mollusca: Bivalvia) 总被引:17,自引:0,他引:17
The phylogenetic relationships among the species belonging to the family Pectinidae are still an issue of debate. The mitochondrial
DNA sequences from the large ribosomal RNA gene may be of great value for systematic and phylogenetic studies within families.
Partial sequences of the 16S rRNA gene were obtained for the scallop species Adamussium colbecki, Aequipecten opercularis, Chlamys glabra, C. islandica, C. varia, and Pecten jacobeus and compared with the published sequence of Pecten maximus. The present molecular data show that Chlamys are polyphyletic and do not support the assignment of these species to the two subfamilies Chlamydinae and Pectininae. Moreover,
the minimal genetic distance between P. maximus and P. jacobeus suggests that they could belong to the same species.
Received: 24 May 1999 / Accepted: 1 September 1999 相似文献
16.
James R. Brown Frank T. Robb Robert Weiss W. Ford Doolittle 《Journal of molecular evolution》1997,45(1):9-16
Each amino acid is attached to its cognate tRNA by a distinct aminoacyl-tRNA synthetase (aaRS). The conventional evolutionary
view is that the modern complement of synthetases existed prior to the divergence of eubacteria and eukaryotes. Thus comparisons
of prokaryotic and eukaryotic aminoacyl-tRNA synthetases of the same type (charging specificity) should show greater sequence
similarities than comparisons between synthetases of different types—and this is almost always so. However, a recent study
[Ribas de Pouplana L, Furgier M, Quinn CL, Schimmel P (1996) Proc Natl Acad Sci USA 93:166–170] suggested that tryptophanyl- (TrpRS) and tyrosyl-tRNA (TyrRS) synthetases of the Eucarya (eukaryotes) are more
similar to each other than either is to counterparts in the Bacteria (eubacteria). Here, we reexamine the evolutionary relationships
of TyrRS and TrpRS using a broader range of taxa, including new sequence data from the Archaea (archaebacteria) as well as
species of Eucarya and Bacteria. Our results differ from those of Ribas de Pouplana et al.: All phylogenetic methods support
the separate monophyly of TrpRS and TyrRS. We attribute this result to the inclusion of the archaeal data which might serve
to reduce long branch effects possibly associated with eukaryotic TrpRS and TyrRS sequences. Furthermore, reciprocally rooted
phylogenies of TrpRS and TyrRS sequences confirm the closer evolutionary relationship of Archaea to eukaryotes by placing
the root of the universal tree in the Bacteria.
Received: 7 December 1996 / Accepted: 11 February 1997 相似文献
17.
Short interspersed DNA elements (SINEs) amplify by retroposition either by (i) successive waves of amplification from one
or a few evolving master genes or by (ii) the generation of new master genes that coexist with their progenitors. Individual,
highly conserved, elements of the B1 SINE family were identified from the GenBank nucleotide database using various B1 subfamily
consensus query sequences to determine their integration times into the mouse genome. A comparison of orthologous loci in
various species of the genus Mus demonstrated that four subfamilies of B1 elements have been amplifying within the last 1–3 million years. Therefore, B1 sequences
are generated by coexisting source genes. Additionally, three B1 subfamilies have been concurrently propagated during subspecies
divergence and strain formation in Mus, indicating very recent activity of this retroposon family. The patterns of intra- and interspecies variations of orthologous
loci demonstrate the usefulness of B1 integrations as a phylogenetic tool. A single inconsistency in the phylogenetic trends
was depicted by the presence of a B1 insert in an orthologous locus exclusively in M. musculus and M. pahari. However, DNA sequence analysis revealed that these were independent integrations at the same genomic site. One highly conserved
B1 element that integrated at least 4–6 million years ago suggests the possibility of occasional function for B1 integrations.
Received: 25 February 2000 / Accepted: 5 June 2000 相似文献
18.
Morgan RO Martin-Almedina S Garcia M Jhoncon-Kooyip J Fernandez MP 《Biochimica et biophysica acta》2006,1763(11):1238-1249
Calcium-binding proteins regulate ion metabolism and vital signalling pathways in all living organisms. Our aim is to rationalize the molecular basis of their function by studying their evolution using computational biology techniques. Phylogenetic analysis is of primary importance for classifying cognate orthologs; profile hidden Markov models (HMM) of individual subfamilies discern functionally relevant sites by conservation probability analysis; and 3-dimensional structures display the integral protein in context. The major classifications of calcium-binding proteins, viz. EF-hand, C2 and ANX, exhibit structural diversity in their HMM fingerprints at the subfamily level, with functional consequences for protein conformation, exposure of receptor interaction sites and/or binding to membrane phospholipids. Calmodulin, S100 and annexin families were characterized in Petromyzon marinus (sea lamprey) to document genome duplication and gene creation events during the key evolutionary transition to primitive vertebrates. Novel annexins from diverse organisms revealed calcium-binding domains with accessory structural features that define their unique molecular fingerprints, protein interactivity and functional specificity. These include the first single-domain, bacterial annexin in Cytophaga hutchinsonii, the 21 tetrad annexins from the unicellular protist Giardia intestinalis, an ancestor to land plant annexins from the green alga Ostreococcus lucimarinus, invertebrate octad annexins and a critical polymorphism in human ANXA7. Receptor docking models supported the hypothesis of a potential interaction between annexin and C2 domains as a propitious mechanism for ensuring membrane translocation during signal transduction. 相似文献
19.
Sol3 transposons are mobile elements defined by long terminal inverted repeats which are found in tomato and potato. Members of
the Sol3 family have been isolated from a variety of solanaceous species including Solanum tuberosum (potato), S. demissum, S. chacoense, Lycopersicon esculentum (tomato), and L. hirsutum. While highly conserved elements are found within different species, Sol3 terminal inverted repeats can also flank unrelated sequences. Southern blot analysis indicates that Sol3 elements are less prevalent in the potato (approximately 50 copies) than in the tomato (>100 copies) genome. No Sol3-hybridizing sequences were observed in tobacco. While a number of Sol3 elements ranging in size from 500 bp to 2 kbp were sequenced, no transposase coding domains could be identified within the
internal regions of the elements. The data suggest that the Sol3 represent a heterogeneous family of nonautonomous transposable elements associated with an as-yet-unidentified autonomous
transposon.
Received: 18 September 1996 / Accepted: 11 March 1997 相似文献
20.
Gilles Bena Marie-France Jubier Isabelle Olivieri Bernard Lejeune 《Journal of molecular evolution》1998,46(3):299-306
We have estimated the potential phylogenetic utility of the ribosomal external transcribed spacer (ETS) from the nuclear
ribosomal region. The ETS was sequenced from 13 annual Medicago (Fabaceae) species upstream a highly conserved motive which was found among many different organisms. In the genus Medicago, the ETS was found to evolve 1.5 times faster than the internal transcribed spacer and to be 1.5 times more informative. Reduced
ribosomal maturation process constraints on ETS are proposed to explain the different evolutionary rates between the two spacers.
Maximal phylogenetic resolution and support was obtained when the two spacers were analyzed together. No incongruence between
the two spacers was found and ETS appears to be a valuable source of information for solidifying ITS plant phylogeny. The
phylogeny obtained in Medicago suggests that none of the three subsections included in the study is monophyletic.
Received: 15 April 1997 / Accepted: 29 July 1997 相似文献