Structure and evolution of the small subunit ribosomal RNA gene of Crithidia fasciculata

Schnare, Murray N.; Collings, James C.; Gray, Michael W.

doi:10.1007/bf00418414

Cited by 46 publications

(26 citation statements)

References 49 publications

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“…1. The alignments were based on the juxtaposition of primary and secondary structures that are conserved in eukaryotic smallsubunit rRNAs and were influenced by sequences not shown from rabbit (20), rat (21), Xehopus laevis (22) (14), Crithidia fasciculata (35), and Euglena gracilis (14). The lengths of the C. reinhardtii, 0. danica, and A. bisexualis coding regions are 1791, 1789, and 1809 nucleotides, respectively, and they define transcripts that contain all of the primary and secondary structure features found in other eukaryotic small-subunit rRNAs.…”

Section: Resultsmentioning

confidence: 99%

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Gunderson¹,

Elwood²,

Ingold³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

352

129

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The phylogenetic relationships among the chlorophyte Chlamydomnonas reinhardtii, the chrysophyte Ochromonas danica, and the oomycete Achlya bisexualis were explored by comparing the sequences of their small-subunit ribosomal RNA coding regions. Comparisons of similarity values or inspection of phylogenetic trees constructed by distance matrix methods reveal a very close relationship between oomycetes and chrysophytes. The separation of chrysophytes from chlorophytes is comparable to that of plants from animals, and both separations are far antedated by the divergence of a number of other protist groups.Traditional analyses based on phenotypic criteria frequently depict chlorophytes (green algae) and chrysophytes (goldenbrown algae) as representatives of lineages that diverged soon after the appearance of the earliest protists (1, 2). Comparisons of numerous characteristics such as features of nuclear division, chloroplast structure and pigment types, kinetid ultrastructure, the nature of the cell wall, and mitochondrial crista structure suggest a long and separate evolutionary history for these algal lineages. The presence of tubular mitochondrial cristae in chrysophytes and lamellar mitochondria cristae in chlorophytes (3) may be particularly significant. Since no recognizably monophyletic protistan groups are split with respect to crista type, and related groups seem to be connected by this characteristic, fundamental differences in mitochondrial structure are thought to reflect ancient divergences and to be of significance at a high taxonomic level.Certain colorless protistan lineages may be more closely related to the chrysophytes than to the chlorophytes. Among these groups are the "lower" fungi. These forms are widely regarded as a polyphyletic assemblage of uncertain relationships to "higher" fungi (4). For example, the oomycetes have traditionally been grouped with the "true" fungi but comparisons of several biochemical and morphological characteristics suggest a close relationship to xanthophytes and chrysophytes (4-7). Taxonomic placement of the oomycetes is still controversial; in some schemes they are grouped with the higher fungi (8), and in others they are grouped with the chrysophytes and their relatives (9, 10).Since there is little agreement about which phenotypic characteristics are most reliable for inferring evolutionary relationships, a consensus phylogeny for protists has never emerged. A phylogenetic tree, which reflects true genotypic similarity, can be inferred from comparisons of macromolecular sequences. Ribosomal RNAs have been used extensively for measuring evolutionary distances (11, 12) and these can be converted into phylogenetic trees by parsimony or distance matrix analyses. Because of their large size (relative to that of 5S and 5.8S rRNAs) and the existence of highly conserved and partially conserved sequence elements, the 16S-like or small-subunit rRNAs have been particularly useful for measuring both close and distant phylogenetic relationships (13,14). As part of a...

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Section: Resultsmentioning

confidence: 99%

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Gunderson¹,

Elwood²,

Ingold³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

352

129

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“…Due to the limitations of the fragment method, when applied to distantly related species, we cannot currently determine the relative relationships among the major lineages. This task will require the analysis of a more slowly evolving molecule, such as rRNA (38,39) or the coding region of intracellular proteins (17). Nonetheless, the major lineages of nuclear DNA accurately reflect divisions established by organismal and molecular criteria of these species.…”

Section: Discussionmentioning

confidence: 99%

Evolution of the genus Leishmania as revealed by comparisons of nuclear DNA restriction fragment patterns.

Beverley¹,

Ismach²,

Pratt³

1987

Proc. Natl. Acad. Sci. U.S.A.

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Restriction endonuclease DNA fragment patterns have been used to examine the relationships among 28 isolates of Leishmania as well as Crithidia, Endotrypanum, and Trypanosoma cruzi. Fragments of nuclear DNA were generated with six restriction enzymes, and blots were hybridized with probes from three loci. Among the major lineages the fragment patterns are essentially completely different, while within the major lineages various degrees of divergence are found. Molecular evolutionary trees were constructed using the method of Nei and Li to estimate the percent nucleotide sequence divergence among strains from the fraction of fragments shared.Defined groups, such as species or subspecies within the major lineages, are also grouped by nuclear DNA comparisons. Within the donovani complex, we find Leishmania donovani chagasi and Leishmania donovani infantum to be as similar as strains within Leishmania donovani donovani, consistent with the proposal by other workers that New World visceral leishmaniasis originated quite recently.Protozoans belonging to the genus Leishmania are frequently parasites in humans, causing a spectrum of diseases whose severity ranges from mild through severely disfiguring to lethal (1). A variety of clinical, biological, and geographical criteria were initially used to classify species (1). With further study it became evident that geographical and pathological criteria were often inadequate to discriminate among different isolates, and biochemical and molecular approaches were employed, including comparisons of isoenzymes (2-5), kinetoplast DNA (6-9), proteins (10), and antigens (11)(12)(13)(14) Comparisons of nuclear DNA have been successfully employed in other organisms for the estimation of temporal and cladistic relationships of species (18)(19)(20). We used Southern blot hybridization with various defined nuclear DNA probes to obtain data that was analyzed by the method of Nei and Li (21) to estimate first the fraction of DNA fragments shared among species and then the percent of nucleotide sequence divergence. This method yields results that generally agree with comparisons of DNA sequences or of other parameters (refs. 20,22,and 23; personal communication). However, the calculation of percent divergence assumes that all fragment differences are attributable to point mutations. This assumption may not always be valid for nuclear DNA, where the presence of detectable length mutations would lower the fraction of fragments shared between two species and thus inflate the estimate of sequence divergence (24). To detect any anomalies caused by length mutations, we examined three independent regions of the nuclear genome and analyzed each data set separately as well as in combination. Our analysis indicates that the fragment comparison method is indeed suitable for comparisons within the major lineages of Leishmania.

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“…The SSU gene has been sequenced for more than 100 species (Schnare et al 1986;Sogin et al 1986;Dams et al 1988;Looker et al 1988;Herna´ndez et al 1990;Briones et al 1992). Several papers indicate that the SSU rDNA is conserved from a phylogenetic point-of-view in the animal kingdom (Sogin 1994) and also in the Kinetoplastidae (Schnare et al 1986;Looker et al 1988;Hernandez et al 1990;Uliana et al 1991;Briones et al 1992;Van Eys et al 1992).…”

Section: Introductionmentioning

confidence: 96%

Polymorphism analysis of the internal transcribed spacer and small subunit of ribosomal RNA genes of Leishmania mexicana

Berzunza-Cruz¹,

Cabrera

Crippa-Rossi³

et al. 2002

Parasitology Research

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Leishmania mexicana causes a wide spectrum of clinical diseases. In spite of the variety of clinical forms, no data exist regarding genetic polymorphism of L. mexicana. We analyzed the polymorphism of the internal transcribed spacer (ITS) and the small subunit rRNA genes of 3 reference strains and 24 Mexican isolates of L. mexicana, by means of polymerase chain reaction and subsequent digestion by restriction enzymes. All strains of L. mexicana had invariant patterns for both the ITS and the small subunit of rRNA genes. Leishmania amazonensis and Leishmania venezuelensis displayed polymorphism only in the ITS. The high degree of identity of this region was confirmed by sequencing DNA from three L. mexicana isolates. There was almost complete identity of the sequence for the ITS region of L. venezuelensis and that of strains of Leishmania major, suggesting that these species may be more closely related than previously thought.

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Structure and evolution of the small subunit ribosomal RNA gene of Crithidia fasciculata

Cited by 46 publications

References 49 publications

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Evolution of the genus Leishmania as revealed by comparisons of nuclear DNA restriction fragment patterns.

Polymorphism analysis of the internal transcribed spacer and small subunit of ribosomal RNA genes of Leishmania mexicana

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