Molecular and Biochemical Parasitology 76 (1996) 31-42 zyxwvutsrqponmlkjihgfedcbaZYXWV MOLECULAR zyxwvuts EmcAL PARAsIToLoGy Self-fertilisation in zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ Try panosoma brucei Andrew Tait”, Norma Buchanana, Geof Hide”, C. Michael R. Turnerb.* zyxwvutsrqponm a W ellcome Unit oj‘ Molecular Parasitology, The Anderson College, University of’ Glasgoas, 56 DumbarronRoad, Glasgow GII 6NU. UK bI.B.L.S.-D.I.I.. Joseph Bluck Building. Unitlersity sf Glasgobts, Glasgovv Gl2 8QQ. UK Received 27 July 1995; revised 2 November 1995; accepted 3 November 1995 zyxwvutsrqponmlkjihgfedcbaZ Abstract We have investigated whether Try panosoma brucei can undergo self-fertilisation. A group of 27 metacyclic clones derived from the tsetse transmission of a mixture of two genetically marked stocks was analysed and 22 clones were observed to be of non-hybrid phenotype. A group of 10 clones from this non-hybrid subset were then analysed for one isoenzyme, one restriction fragment length polymorphism and three karyotype markers potentially informative for the detection of self-fertilisation. Five of the 10 clones were found to be recombinant for at least one marker and we interpret these recombination events as indicating the clones to be products of self-fertilisation. We have also analysed a limited number of metacyclic clones from stocks of T. brucei each singly transmitted through tsetse flies but, so far, no evidence of recombination has been detected. We conclude that T. brucei is able to self-fertilise but there may be a requirement for the presence of dissimilar stocks to initiate such an event. Keywords: Trypanosoma brucei; Genetics; Self-fertilisation; Karyotype 1. Introduction Genetic exchange in Try panosoma brucei has been directly demonstrated by laboratory crosses [I -71 but its contribution to the epidemiology of African trypanosomiasis in the field remains a matter of debate [&13]. By infecting tsetse flies with two genetically marked cloned stocks of trypanosomes, it has been shown that mating takes place during development in the fly and that _~ Abbreuiutions: STIB, Swiss Tropical Institute Basel; EATRO, East African Trypanosomiasis Research Organisa- tion; RFLP, restriction fragment length polymorphism; PFGE, pulsed field gel electrophoresis; AP, alkaline phos- phatase; ICD, isocitrate dehydrogenase; ME,, malic enzyme B; Tyr3. tyrosyl tyrosyl tyrosine peptidase; p/c, phospholipase C gene: pgk. phosphoglycerate kinase gene. * Corresponding author. Tel.: + 44 141 330 6629; Fax: + 44 141 307 8016; E-mail: c.m.turner@udcf.gla.ac.uk. a proportion of such mixed-infected flies produce metacyclic trypanosomes which are hybrid for the range of markers examined [l-7]. A propor- tion of the trypanosomes emerging from such flies are, however, parental in genotype and phenotype implying that the mating events are non-obliga- tory during the life-cycle of the trypanosome [2- 71. In order to investigate the rules and 0166~6851/96/$15.00 0 1996 Elsevier Science Ireland Ltd. All rights reserved SSDI 0166-6851(95)02528-L