Genome analyses suggest the presence of polyploidy and recent human-driven expansions in eight global populations of the honeybee pathogen Nosema ceranae.
Nosema ceranae is a microsporidian pathogen whose infections have been associated with recent global declines in the populations of western honeybees (Apis mellifera). Despite the outstanding economic and ecological threat that N. ceranae may represent for honeybees worldwide, many aspects of its biology, including its mode of reproduction, propagation and ploidy, are either very unclear or unknown. In the present study, we set to gain knowledge in these biological aspects by re-sequencing the genome of eight isolates (i.e. a population of spores isolated from one single beehive) of this species harvested from eight geographically distant beehives, and by investigating their level of polymorphism. Consistent with previous analyses performed using single gene sequences, our analyses uncovered the presence of very high genetic diversity within each isolate, but also very little hive-specific polymorphism. Surprisingly, the nature, location and distribution of this genetic variation suggest that beehives around the globe are infected by a population of N. ceranae cells that may be polyploid (4n or more), and possibly clonal. Lastly, phylogenetic analyses based on genome-wide single-nucleotide polymorphism data extracted from these parasites and mitochondrial sequences from their hosts all failed to support the current geographical structure of our isolates.
Canadian Institute for Advanced Research, Department of Biology; University of Ottawa, Ottawa, ON, Canada.
Adrian
A
Pelin
Canadian Institute for Advanced Research, Department of Biology; University of Ottawa, Ottawa, ON, Canada.
Mohammed
M
Selman
Departments of Biology and of Mathematics & Statistics, University of Ottawa, Ottawa, ON, Canada.
Stéphane
S
Aris-Brosou
FASTERIS S.A., Ch. du Pont-du-Centenaire 109, P.O. Box 28, Plan-les-Ouates, CH-1228, Geneva, Switzerland.
Laurent
L
Farinelli
Canadian Institute for Advanced Research, Department of Biology; University of Ottawa, Ottawa, ON, Canada.
Nicolas
N
Corradi
D000818:Animals; D001483:Base Sequence; D001516:Bees / Q000382:microbiology*; D004271:DNA, Fungal / Q000235:genetics*; D005843:Geography; D015810:Linkage Disequilibrium / Q000235:genetics; D016818:Nosema / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny; D011110:Polymorphism, Genetic / Q000235:genetics; D011123:Polyploidy; D017422:Sequence Analysis, DNA
D004271:DNA, Fungal