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  • 1
    ISSN: 1432-1432
    Keywords: Entamoeba histolytica ; Protozoa lacking mitochondria ; Eukaryotic kingdoms ; Elongation factor-1α ; Maximum likelihood ; Protein phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phylogenetic analyses of ribosomal RNA sequences have played an important role in the study of early evolution of life. However, Loomis and Smith suggested that the ribosomal RNA tree is sometimes misleading—especially when G+C content differs widely among lineages—and that a protein tree from amino acid sequences may be more reliable. In this study, we analyzed amino acid sequence data of elongation factor-1α by a maximum likelihood method to clarify branching orders in the early evolution of eukaryotes. Contrary to Sogin et al.'s tree of small-subunit ribosomal RNA, a protozoan species, Entamoeba histolytica, that lacks mitochondria was shown to have diverged from the line leading to eukaryotes with mitochondria before the latter separated into several kingdoms. This indicates that Entamoeba is a living relic of the earliest phase of eukaryotic evolution before the symbiosis of protomitochondria occurred. Furthermore, this suggests that, among eukaryotic kingdoms with mitochondria, Fungi is the closest relative of Animalia, and that a cellular slime mold, Dictyostelium discoideum, had not diverged from the line leading to Plantae-Fungi-Animalia before these three kingdoms separated.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 31 (1990), S. 205-210 
    ISSN: 1432-1432
    Keywords: Isozyme ; Intron ; Phylogenetic tree ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Both the mouse cytosolic malate dehydrogenase gene and its mitochondrial counterpart contain eight introns, of which two are present at identical positions between the isozyme genes. The probability that the two intron positions coincide by chance between the two genes has been shown to be significantly small (=1.3×10−3), suggesting that the conservation of the intron positions has a biological significance. On the basis of a rooted phylogenetic tree inferred from a comparison of these isozymes and lactate dehydrogenases, we have shown that the origins of the conserved introns are very old, possibly going back to a date before the divergence of eubacteria, archaebacteria, and eukaryotes. In the aspartate aminotransferase isozyme genes, five of the introns are at identical places. The origins of the five conserved introns, however, are not obvious at present. It remains possible that some or all of the conserved introns have evolved after the divergence of eubacteria and eukaryotes.
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  • 3
    ISSN: 1432-1432
    Keywords: Key words: Protein tyrosine phosphatase — Classification — Sponge — Gene duplication — Phylogenetic tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. 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.
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  • 4
    ISSN: 1432-1432
    Keywords: Key words: G protein — Tyrosine kinase — Sponge — Gene duplication — Cambrian explosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. 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.
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  • 5
    ISSN: 1432-1432
    Keywords: Key words: Divergence time — Molecular clock — Aldolase — Triose phosphate isomerase — Sponge — Amphioxus — Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. 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.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1432
    Keywords: Key words:Pax-2/5/8— Sponge — Gene duplication — Pax family — Cambrian explosion — Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Members of the Pax gene family encode transcription factors containing a DNA-binding paired domain which is involved in developmental control and the formation of the central nervous system (CNS). The family members are classified into six classes or subfamilies, depending on the presence or absence of paired-type homeobox and octapeptide. To obtain rough estimates of times when the different classes of the Pax family diverged by gene duplication, we cloned and sequenced a Pax-related cDNA, sPax-2/5/8, from Ephydatia fluviatilis, a freshwater sponge, which encodes a paired-type homeobox and an octapeptide, in addition to a paired domain. A phylogenetic tree based on the paired domain sequences suggest that sPax-2/5/8 is a homologue of vertebrate Pax-2/5/8. It was also suggested that the majority of gene duplications that gave rise to distinct classes has been completed in the very early evolution of animals before the parazoan–eumetazoan split. Long after the ancient gene duplications, further gene duplications that gave rise to members in each subfamily occurred on the chordate lineages and completed before the fish–tetrapod split. This suggests that the major classes of the Pax genes involved in the formation of CNS characteristic of triploblasts had already existed long before the Cambrian explosion of triploblasts, and there is no direct link between the creation of new genes with novel functions and the Cambrian explosion. The pattern of gene diversification found in the Pax family is similar to those in five gene families involved in the signal transduction analyzed by us. Furthermore, the evolutionary rates of the Pax proteins have been shown to decrease with increasing organismal complexity during animal evolution.
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  • 7
    ISSN: 1432-1432
    Keywords: Phylogenetic tree ; Likelihood method ; RNA polymerase ; Archaebacteria ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The amino acid sequences of the largest subunits of the RNA polymerases I, II, and III from eukaryotes were compared with those of archaebacterial and eubacterial homologs, and their evolutionary relationships were analyzed in detail by a recently developed tree-making method, the likelihood method of protein phylogeny, as well as by the neighbor-joining method and the parsimony method, together with bootstrap analyses. It was shown that the best tree topologies predicted by the first two methods are identical, whereas the last one predicts a distinct tree. The maximum likelihood tree revealed that, after the separation from archaebacteria, the three eukaryotic RNA polymerases diverged from an ancestral precursor in the eukaryotic lineage. This result is contrasted with the published result showing multiple origins for the three eukaryotic polymerases. It was shown that eukaryotic RNA polymerase I evolved much more rapidly than RNA polymerases II and III: The N-terminal half of RNA polymerase I shows an extraordinarily high evolutionary rate, possibly due to relaxed functional constraints. In contrast the evolutionary rate of archaebacterial RNA polymerase is remarkably limited. In addition, including the second largest subunit of the RNA polymerase, a detailed analysis for the branching pattern of the three major groups of archaebacteria was carried out by the maximum likelihood method. It was shown that the three major groups of archaebacteria are likely to form a single cluster; that is, archaebacteria are likely to be monophyletic as originally proposed by Woese and his colleagues.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 41 (1995), S. 238-246 
    ISSN: 1432-1432
    Keywords: Cellular slime molds ; Animals ; Fungi ; Plantae ; Maximum-likelihood method ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phylogenetic position of Dictyostelium inferred from 18S rRNA data contradicts that from protein data. Protein trees always show the close affinity of Dictyostelium with animals, fungi, and plants, whereas in 18S rRNA trees the branching of Dictyostelium is placed at a position before the massive radiation of protist groups including the divergence of the three kingdoms. To settle this controversial issue and to determine the correct position of Dictyostelium, we inferred the phylogenetic relationship among Dictyostelium and the three kingdoms Animalia, Fungi, and Plantae by a maximum-likelihood method using 19 different protein data sets. It was shown at the significance level of 1 SE that the branching of Dictyostelium antedates the divergence of Animalia and Fungi, and Plantae is an outgroup of the Animalia-Fungi-Dictyostelium clade.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2007-03-20
    Print ISSN: 0014-5793
    Electronic ISSN: 1873-3468
    Topics: Biology , Chemistry and Pharmacology
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