Molecular aspects of phylogenetic relationships among Trypanosoma (Nannomonas) congolense
Abstract
At least four different genotypic groups of Trypanosoma (Nannomonas)
congolense have been described based upon profiles of iso-enzymes, nucleotide
composition of the highly repetitive satellite DNA, restriction fragment length
polymorphisms (RFLPs) of conserved nuclear and kinetoplast DNA sequences and, more
recently, randomly amplified polymorphic DNA (RAPD) patterns. The exact
phylogenetic relationships of these morphologically identical but genetically
heterogeneous parasites is obscure. I have designed specific oligonucleotide primers
based on conserved nucleotide sequences of 18S ribosomal RNA (18S rRNA) gene of
Trypanosoma brucei, Leishmania donovani, Triponema aequale and Lagenidium
gigantum, and used these in the polymerase chain reaction (PCR) to amplify genomic
DNA from four different clones each representing a different genotypic group of T.
congolense. PCR products of approximately 1 kb were generated using as template DNA
from each of the trypanosomes. The nucleotide sequences of a segment of the PCR
products were determined by direct sequencing to provide partial nucleotide sequence
of the 18S rRNA gene in each of the trypanosomes. Using these sequences and those
that have been published for the other Trypanosomatids, sequence similarity scores were
determined with the help of appropriate computer software.
Additionally, primers of arbitrary nucleotide sequence have been employed in the PCR
amplification of genomic DNA from the four trypanosome clones representing the
different T. congolense types. The patterns of randomly amplified polymorphic DNA
(RAPD) have been used in the calculation of pairwise genetic similarity indices among
these trypanosomes without making assumptions regarding relative band intensities.
In a parallel study I have demonstrated that the PCR products of the 18S
rRNA gene are sensitive probes for specific identification of trypanosomes. I have used
heterologous PCR products as probes in hybridization analyses of genomic DNA and
PCR products from the different types of T. congolense and from other protozoa. The
RFLPs observed confirmed heterogeneity of the 18S rRNA gene sequences among the
trypanosomes comprising the subgenus Nannomonas.
Citation
Osanya, A(1995). Molecular aspects of phylogenetic relationships among Trypanosoma (Nannomonas) congolenseSponsorhip
University of NairobiPublisher
Department of Biochemistry, University of Nairobi
Description
Msc Thesis