Abstract
BackgroundGenetic exchange has been described in several kinetoplastid parasites, but the most well-studied mating system is that of Trypanosoma brucei, the causative organism of African sleeping sickness. Sexual reproduction takes place in the salivary glands (SG) of the tsetse vector and involves meiosis and production of haploid gametes. Few genetic crosses have been carried out to date and consequently there is little information about the mating compatibility of different trypanosomes. In other single-celled eukaryotes, mating compatibility is typically determined by a system of two or more mating types (MT). Here we investigated the MT system in T. brucei.MethodsWe analysed a large series of F1, F2 and back crosses by pairwise co-transmission of red and green fluorescent cloned cell lines through experimental tsetse flies. To analyse each cross, trypanosomes were cloned from fly SG containing a mixture of both parents, and genotyped by microsatellites and molecular karyotype. To investigate mating compatibility at the level of individual cells, we directly observed the behaviour of SG-derived gametes in intra- or interclonal mixtures of red and green fluorescent trypanosomes ex vivo.ResultsHybrid progeny were found in all F1 and F2 crosses and most of the back crosses. The success of individual crosses was highly variable as judged by the number of hybrid clones produced, suggesting a range of mating compatibilities among F1 progeny. As well as hybrids, large numbers of recombinant genotypes resulting from intraclonal mating (selfers) were found in some crosses. In ex vivo mixtures, red and green fluorescent trypanosome gametes were observed to pair up and interact via their flagella in both inter- and intraclonal combinations. While yellow hybrid trypanosomes were frequently observed in interclonal mixtures, such evidence of cytoplasmic exchange was rare in the intraclonal mixtures.ConclusionsThe outcomes of individual crosses, particularly back crosses, were variable in numbers of both hybrid and selfer clones produced, and do not readily fit a simple two MT model. From comparison of the behaviour of trypanosome gametes in inter- and intraclonal mixtures, we infer that mating compatibility is controlled at the level of gamete fusion.
Highlights
Genetic exchange has been described in several kinetoplastid parasites, but the most well-studied mating system is that of Trypanosoma brucei, the causative organism of African sleeping sickness
Mating compatibility is often controlled by a system of mating types (MT), such that mating between cells of different MT is preferred over same MT
The most well-studied mating system is that of T. brucei, the causative organism of African sleeping sickness, which is transmitted by an insect vector, the tsetse fly
Summary
Genetic exchange has been described in several kinetoplastid parasites, but the most well-studied mating system is that of Trypanosoma brucei, the causative organism of African sleeping sickness. The most well-studied mating system is that of T. brucei, the causative organism of African sleeping sickness, which is transmitted by an insect vector, the tsetse fly. It is during the developmental cycle of T. brucei within the salivary glands of the fly that mating occurs [11]. The biparental inheritance of kinetoplast DNA (kDNA) has implications for the inheritance of cell organelles, because the kinetoplast is structurally linked to the basal body of the single flagellum via a tripartite attachment complex [21]. It follows from the observation that hybrid progeny have hybrid kinetoplast DNA networks, that zygote formation involves fusion of cell bodies and not just the exchange of nuclei as seen for example in ciliates [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
