Kinetoplast DNA minicircles are inherited from both parents in genetic crosses of Trypanosoma brucei

Abstract

In the order Kinetoplastida, genetic exchange has been demonstrated only in the genus Trypanosoma. Analysis of kinetoplast DNA (kDNA) in genetic crosses of T. brucei has shown that whereas maxicircles are inherited uniparentally, minicircles are inherited from both parents. This result was confirmed for a new cross of T. b. brucei and T. b. rhodesiense by restriction enzyme digestion and Southern analysis of purified kDNA. By hybridisation with small minicircle-derived probes, we could demonstrate the presence of particular parental minicircles in the kDNA of hybrid progeny clones. All hybrid clones had inherited two minicircles from one parent despite two of the four clones having maxicircles from the other parent. The results suggest that rather than small-scale exchange of minicircles between parental networks, gross breakdown and reassembly of the minicircle network occurs during genetic exchange.

A novel GFP approach for the analysis of genetic exchange in trypanosomes allowing the in situ detection of mating events

“…Analysis of the inheritance of genetic markers in hybrid progeny suggests that a meiotic division occurs at some stage Sternberg et al, 1988Sternberg et al, , 1989Gibson, 1989;Turner et al, 1990;Gibson & Stevens, 1999), but triploid hybrids also occur with some frequency Wells et al, 1987;Gibson et al, 1992Gibson et al, , 1997bGibson & Bailey, 1994;Hope et al, 1999) and a haploid life cycle stage has not been found (Shapiro et al, 1984;Tait et al, 1989). The observation that kinetoplast (mitochondrial) DNA is inherited from both parents in hybrid progeny supports the surprising suggestion that somehow the complex parental kinetoplast DNA networks swap DNA (Gibson & Garside, 1990;Turner et al, 1995;Gibson et al, 1997a). This in turn presupposes fusion of the parental mitochondria, and hence cells, during genetic exchange.…”

Multiple Mitochondrial Introgression Events and Heteroplasmy in Trypanosoma cruzi Revealed by Maxicircle MLST and Next Generation Sequencing

“…However, the demonstration of heteroplasmy in this study suggests that, following genetic exchange, any minor maxicircle genotypes may be undetectable using conventional sequencing techniques. In addition, evidence of bi-parental transmission of both maxicircles [73], [74] and minicircles [75] in experimentally-derived T. brucei hybrids indicates that this phenomenon can occur in kinetoplastids as a result of recombination. The mechanism of genetic exchange in T. cruzi [24] differs from meiosis, which is observed in T. brucei [73], [76].…”

RNA editing in kinetoplastids

“…Furthermore, it has been shown for T. brucei that both, mini and maxicirlces are exchanged between cells during the transition through the insect host, indicating a mechanism for the maintenance of diversity. [32][33][34] today are involved in changing the mRNA sequence, resulting in an altered protein product. However, when RNA editing was discovered in trypanosomes, by Benne and co-workers it was merely thought to be yet another odd mechanism of "primitive" protozoa.…”