Caught in the act: trypanosome sex visualised for the first time
22 February 2011
Trypanosomes are single-celled parasites that cause sleeping sickness in humans and wasting diseases in livestock. They are transmitted by the tsetse fly and, until now, it was unclear whether they reproduce sexually or asexually, because this stage in their life cycle occurs inside the insect carrier.
Sexual reproduction produces offspring that inherit half their genetic material from each parent. The alternative is asexual reproduction, where the offspring inherit all genetic material from a single parent.
Sexual reproduction is important in organisms that cause diseases because it can spread genes that make them more virulent, or resistant to drugs used for treatment, as well as creating completely new strains with combinations of genes not previously encountered.
Some time ago it was shown that genetic shuffling could occur when two different trypanosome strains were mixed in the tsetse fly, but it was far from clear that this was true sexual reproduction. It was difficult to visualise the process directly because it happened inside the insect.
To get round this problem, Professor Wendy Gibson and colleagues used fluorescently tagged proteins to make trypanosomes light up like tiny lightbulbs. They tagged proteins that function only during meiosis, the process of cellular division at the core of sexual reproduction that shuffles the parental genes and deals them out in new combinations to the offspring.
Professor Gibson said: “It seems that meiosis in trypanosomes has eluded observers because it occurs hidden inside the insect carrying the parasite - a difficult and technically challenging system to work with. These new results will further our understanding of events at the very beginning of eukaryote evolution, and of the way that new strains of disease-causing microbes emerge.”
The study, carried out by researchers from Bristol’s Schools of Biological Sciences and Veterinary Sciences in collaboration with the University of Cambridge, is published this week in 'Proceedings of the National Academy of Sciences USA'.
The research was funded by the Wellcome Trust.
Image: Professor Wendy Gibson and colleagues used fluorescently tagged proteins to make trypanosomes light up like tiny lightbulbs. Credit: Peacock et al., 'Proceedings of the National Academy of Sciences USA'.
Reference
Peacock L et al. Identification of the meiotic life cycle stage of Trypanosoma brucei in the tsetse fly. Proc Natl Acad Sci USA 2011 [Epub ahead of print].
