Genetic exchange in Trypanosoma brucei brucei: variable chromosomal location of housekeeping genes in different trypanosome stocks

Gibson, Wendy; Garside, Lisa

doi:10.1016/0166-6851(91)90029-6

Cited by 46 publications

(19 citation statements)

References 27 publications

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“…In addition to the ORF, the modification altered the 5′ UTR, but the 3′ UTR was unaltered and expression relied on endogenous transcription. The modifications were performed in cultured procyclic lines of the mating-competent T. b. brucei strain J10 (6,28), and all cell lines were taken through at least one complete life cycle.…”

Section: Resultsmentioning

confidence: 99%

Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly

Peacock

Ferris

Sharma

et al. 2011

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

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Elucidating the mechanism of genetic exchange is fundamental for understanding how genes for such traits as virulence, disease phenotype, and drug resistance are transferred between pathogen strains. Genetic exchange occurs in the parasitic protists Trypanosoma brucei , T. cruzi , and Leishmania major , but the precise cellular mechanisms are unknown, because the process has not been observed directly. Here we exploit the identification of homologs of meiotic genes in the T. brucei genome and demonstrate that three functionally distinct, meiosis-specific proteins are expressed in the nucleus of a single specific cell type, defining a previously undescribed developmental stage occurring within the tsetse fly salivary gland. Expression occurs in clonal and mixed infections, indicating that the meiotic program is an intrinsic but hitherto cryptic part of the developmental cycle of trypanosomes. In experimental crosses, expression of meiosis-specific proteins usually occurred before cell fusion. This is evidence of conventional meiotic division in an excavate protist, and the functional conservation of the meiotic machinery in these divergent organisms underlines the ubiquity and basal evolution of meiosis in eukaryotes.

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Section: Resultsmentioning

confidence: 99%

Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly

Peacock

Ferris

Sharma

et al. 2011

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

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127

156

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“…6rucei is diploid throughout its life cycle and no haploid gamete stage has been detected (Shapiro et al, 1984;Kooy et al, 1989), although the fleeting or rare occurrence of a haploid life cycle stage cannot be ruled out. Analysis of isoenzymes and RFLPs indicates that a meiotic division probably occurs during genetic exchange : segregation and reassortment of genetic markers is observed (Jenni et al, 1986;Paindavoine et al, 1986;Wells et al, 1987;Gibson, 1989;Sternberg et al, 1989;Turner et al, 1990;Gibson & Garside, 1991;Gibson et al, 1992Gibson et al, ,1995Gibson & Whittington, 1993;Schweizer et al, 1994;Gibson & Bailey, 1994;Degen et al, 1995) and also a high frequency of chromosomal recombination in hybrids (Gibson et al, 1992;Gibson & Bailey, 1994). However, hybrids with a 3n DNA content have been found in four of five crosses for which DNA contents were measured (Paindavoine et al, 1986;Wells et al, 1987;Gibson et al, 1992Gibson et al, , 1995Gibson & Bailey, 1994), including two early crosses which did not employ selectable markers.…”

Section: Introductionmentioning

confidence: 99%

“…In this first successful laboratory cross and several subsequent ones (Gibson, 1989;Turner et al, 1990; Abbreviations: hph, hygromycin phosphotransferase gene; neo, neomycin phosphotransferase gene; H, hygromycin-B-resistant; N, Geneticin (G418)-resistant; ALD, aldolase; GAPDH, glyceraldehyde phosphate dehydrogenase; GPI, glucose phosphate isomerase; PARP,, procyclic acidic repetitive protein; PGK, phosphoglycerate kinase; PLC, phospholipase C; PYK, pyruvate kinase; RAPD, random amplification of polymorphic DNA; RNAP, RNA polymerase; SSC, standard saline citrate; TIM, triose phosphate isomerase; VSG, variant surface glycoprotein. Garside, 1991;Schweizer et al, 1994;Degen et al, 1995), hybrid trypanosomes were detected by laboriously searching through cloned trypanosomes for those with a non-parental phenotype or genotype. The development of methods for the stable transformation of trypanosomes with heterologous genes (Ten Asbroek et al, 1990;Lee & Van der Ploeg, 1991;Eid & SollnerWebb, 1991) led to a new approach: incorporation of selectable markers for drug resistance into the parental trypanosome clones and selection of hybrid trypanosomes by double drug resistance (Gibson & Whittington, 1993).…”

Section: Introductionmentioning

confidence: 99%

Intraclonal mating in Trypanosoma brucei is associated with out-crossing

et al. 1997

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To examine whether mating can occur within as well as between clones of Trypanosoma brucei, we transformed three T. brucei subspecies stocks with heterologous genes conferring resistance to either hygromycin or Geneticin and carried out a series of inter-and intraclone matings in all possible double drug combinations. Double drug-resistant hybrids were recovered from three of the six out-crosses, but not from any of the three intraclone matings. However, further analysis of cloned progeny trypanosomes from one of the out-crosses using RFLP markers, molecular karyotyping and RAPD (random amplification of polymorphic DNA) produced unequivocal evidence that intraas well as interclone mating had occurred. The progeny of interclone mating were double drug-resistant and heterozygous at 9 of 13 loci examined. In contrast, the progeny of intraclone mating had no demonstrable input of genetic material from the hygromycin-resistant parent and were similar to the Geneticin-resistant parent for most markers, except for five loci which were heterozygous in the Geneticin-resistant parent but homozygous in these clones (aldolase, THTl glucose transporter, procyclin, tubulin and cDNA 23). In addition, PFGE showed considerable karyotypic rearrangements in these clones and loss of genetic material was evident from RAPD and VSG (variant surface glycoprotein) gene fingerprint analysis. We conclude that intraclone mating can occur in trypanosomes, but only during out-crossing, suggesting that meiosis and/or fusion are triggered by a diffusible factor.

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“…However, comparison of different T. brucei isolates reveals considerable genetic variability in the form of chromosomal size variation (Gottesdiener et al 1990;Gibson and Garside 1991;Turner et al 1997;Melville et al 1998Melville et al , 1999Melville et al , 2000. Chromosome size polymorphism is not unique to African trypanosomes: It has been observed in Plasmodium and Leishmania, where size variation of 10%-25% has been reported (Janse 1993;Wincker et al 1996), and in T. cruzi, where twofold variation has been observed (Henriksson et al 1995).…”

mentioning

confidence: 99%

“…), and we have observed variation of up to twofold between diploid homologs within a parasite (Melville et al 2000). Yet, mapping projects have failed to identify major DNA translocations or loss of synteny (Melville et al 1998(Melville et al , 2000, and only one instance is reported in the literature (Gibson and Garside 1991).…”

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confidence: 99%

Hemizygous subtelomeres of an African trypanosome chromosome may account for over 75% of chromosome length

Callejas

Leech²,

Reitter³

et al. 2006

Genome Res.

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African trypanosomes are parasitic protozoa that infect a wide range of mammals, including humans. These parasites remain extracellular in the mammalian bloodstream, where antigenic variation allows them to survive the immune response. The Trypanosoma brucei nuclear genome sequence has been published recently. However, the significant chromosome size polymorphism observed among strains and subspecies of T. brucei, where total DNA content may vary up to 30%, necessitates a comparative study to determine the underlying basis and significance of such variation between parasites. In addition, the sequenced strain (Tb927) presents one of the smallest genomes analyzed among T. brucei isolates; therefore, establishing polymorphic regions will provide essential complementary information to the sequencing project. We have developed a Tb927 high-resolution DNA microarray to study DNA content variation along chromosome I, one of the most size-variable chromosomes, in different strains and subspecies of T. brucei. Results show considerable copy number polymorphism, especially at subtelomeres, but are insufficient to explain the observed size difference. Additional sequencing reveals that >50% of a larger chromosome I consists of arrays of variant surface glycoprotein genes (VSGs), involved in avoidance of acquired immunity. In total, the subtelomeres appear to be three times larger than the diploid core. These results reveal that trypanosomes can utilize subtelomeres for amplification and divergence of gene families to such a remarkable extent that they may constitute most of a chromosome, and that the VSG repertoire may be even larger than reported to date. Further experimentation is required to determine if these results are applicable to all size-variable chromosomes.

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Genetic exchange in Trypanosoma brucei brucei: variable chromosomal location of housekeeping genes in different trypanosome stocks

Cited by 46 publications

References 27 publications

Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly

Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly

Intraclonal mating in Trypanosoma brucei is associated with out-crossing

Hemizygous subtelomeres of an African trypanosome chromosome may account for over 75% of chromosome length

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