Genomic confirmation of hybridisation and recent inbreeding in a vector-isolated Leishmania population.
Although asexual reproduction via clonal propagation has been proposed as the principal reproductive mechanism across parasitic protozoa of the Leishmania genus, sexual recombination has long been suspected, based on hybrid marker profiles detected in field isolates from different geographical locations. The recent experimental demonstration of a sexual cycle in Leishmania within sand flies has confirmed the occurrence of hybridisation, but knowledge of the parasite life cycle in the wild still remains limited. Here, we use whole genome sequencing to investigate the frequency of sexual reproduction in Leishmania, by sequencing the genomes of 11 Leishmania infantum isolates from sand flies and 1 patient isolate in a focus of cutaneous leishmaniasis in the Çukurova province of southeast Turkey. This is the first genome-wide examination of a vector-isolated population of Leishmania parasites. A genome-wide pattern of patchy heterozygosity and SNP density was observed both within individual strains and across the whole group. Comparisons with other Leishmania donovani complex genome sequences suggest that these isolates are derived from a single cross of two diverse strains with subsequent recombination within the population. This interpretation is supported by a statistical model of the genomic variability for each strain compared to the L. infantum reference genome strain as well as genome-wide scans for recombination within the population. Further analysis of these heterozygous blocks indicates that the two parents were phylogenetically distinct. Patterns of linkage disequilibrium indicate that this population reproduced primarily clonally following the original hybridisation event, but that some recombination also occurred. This observation allowed us to estimate the relative rates of sexual and asexual reproduction within this population, to our knowledge the first quantitative estimate of these events during the Leishmania life cycle.
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom ; Centre for Immunology and Infection, Department of Biology, University of York, York, United Kingdom.
Matthew B
MB
Rogers
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
Tim
T
Downing
Centre for Immunology and Infection, Department of Biology, University of York, York, United Kingdom.
Barbara A
BA
Smith
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom ; Unit of Molecular Parasitology, Department of Parasitology, Institute of Tropical Medicine, Antwerp, Belgium.
Hideo
H
Imamura
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
Mandy
M
Sanders
Department of Parasitology, Fac. Sci., Charles University, Prague, Czech Republic.
Milena
M
Svobodova
Department of Parasitology, Fac. Sci., Charles University, Prague, Czech Republic.
Petr
P
Volf
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
Matthew
M
Berriman
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom.
James A
JA
Cotton
Centre for Immunology and Infection, Department of Biology, University of York, York, United Kingdom.
Deborah F
DF
Smith
D000818:Animals; D005828:Genetics, Population; D006801:Humans; D006824:Hybridization, Genetic; D007178:Inbreeding; D007303:Insect Vectors / Q000235:genetics; D007891:Leishmania / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D007896:Leishmaniasis / Q000235:genetics / Q000469:parasitology* / Q000635:transmission; D008018:Life Cycle Stages / Q000235:genetics; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats / Q000235:genetics; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction / Q000235:genetics; D014421:Turkey