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Evidence that the mechanism of gene exchange in Trypanosoma brucei involves meiosis and syngamy

Published online by Cambridge University Press:  06 April 2009

C. M. R. Turner ,
J. Sternberg ,
N. Buchanan ,
E. Smith ,
G. Hide  and
A. Tait
C. M. R. Turner
Affiliation:
Department of Zoology, University of Glasgow, Glasgow G12 8QQ
J. Sternberg
Affiliation:
Department of Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT
N. Buchanan
Affiliation:
Wellcome Unit of Molecular Parasitology, Department of Veterinary Parasitology, University of Glasgow, Bearsden Road, Glasgow G61 1QH
E. Smith
Affiliation:
Department of Zoology, University of Glasgow, Glasgow G12 8QQ
G. Hide
Affiliation:
Wellcome Unit of Molecular Parasitology, Department of Veterinary Parasitology, University of Glasgow, Bearsden Road, Glasgow G61 1QH
A. Tait
Affiliation:
Wellcome Unit of Molecular Parasitology, Department of Veterinary Parasitology, University of Glasgow, Bearsden Road, Glasgow G61 1QH
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Summary

All pairwise combinations of three cloned stocks of Trypanosoma brucei (STIB 247L, STIB 386AA and TREU 927/4) were co-transmitted through tsetse flies (Glossina morsitans) and screened for the production of hybrid trypanosomes. Clones of metacyclic and bloodstream trypanosomes from flies harbouring mature infections containing hybrid trypanosomes were established and screened for several isoenzyme and restriction fragment length polymorphisms. For each of the three combinations of parents, some progeny clones were observed to be of a phenotype and genotype indicating that genetic exchange had occurred during development of the trypanosomes in flies. These hybrid clones shared three salient features: (1) where the parents were homozygous variants the progeny were heterozygous, (2) where one of the parents was heterozygous, allelic segregation was observed and (3) the progeny clones were shown to be recombinant when two or more markers for which one of the parents was heterozygous were examined. These results are consistent with the progeny being an F1 in a diploid mendelian genetic system involving meiosis and syngamy. Our observations show that all possible combinations of the three stocks may undergo genetic exchange. A marker analysis of a series of clones each derived from single metacyclic trypanosomes showed that individual flies transmit a mixture of trypanosome genotypes corresponding to F1 progeny and to parental types, indicating that genetic exchange was a non-obligatory event in the life-cycle of the trypanosome. In addition, a preliminary analysis of the phenotype of procyclic stage trypanosomes derived from flies infected with two stocks, indicates that genetic exchange is unlikely to occur at this stage.

Keywords

Trypanosoma bruceigenetic exchangemeiosisrecombination
Type
Research Article
Information
Parasitology , Volume 101 , Issue 3 , December 1990 , pp. 377 - 386
Copyright
Copyright © Cambridge University Press 1990

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