title: Polymorphism and recombination for rDNA in the putatively asexual microsporidian Nosema ceranae, a pathogen of honeybees.
abstract: Nosema ceranae is currently one of the major pathogens of honeybees, related to the worldwide colony losses phenomenon. The genotyping of strains based on ribosomal DNA (rDNA) can be misleading if the repeated units are not identical. The analysis of cloned rDNA fragments containing the intergenic spacer (IGS) and part of the rDNA small-subunit (SSU) gene, from N. ceranae isolates from different European and Central Asia populations, revealed a high diversity of sequences. The variability involved single-nucleotide polymorphisms and insertion/deletions, resulting in 79 different haplotypes. Two sequences from the same isolate could be as different as any pair of sequences from different samples; in contrast, identical haplotypes were also found in very different geographical origins. Consequently, haplotypes cannot be organized in a consistent phylogenetic tree, clearly indicating that rDNA is not a reliable marker for the differentiation of N. ceranae strains. The results indicate that recombination between different sequences may produce new variants, which is quite surprising in microsporidia, usually considered to have an asexual mode of reproduction. The diversity of sequences and their geographical distribution indicate that haplotypes of different lineages may occasionally be present in a same cell and undergo homologue recombination, therefore suggesting a sexual haplo-diploid cycle.
authors.affiliation: Universidad San Pablo-CEU, Biology Department, 28668 Montepríncipe, Spain.Centro Apícola Regional, Bee Pathology Laboratory, 19180 Marchamalo, Guadalajara, Spain.
authors.forename: Soledad
authors.initials: S
authors.lastname: Sagastume
authors.affiliation: Universidad San Pablo-CEU, Biology Department, 28668 Montepríncipe, Spain.Centro Apícola Regional, Bee Pathology Laboratory, 19180 Marchamalo, Guadalajara, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Del Águila
authors.affiliation: Universidad San Pablo-CEU, Biology Department, 28668 Montepríncipe, Spain.Centro Apícola Regional, Bee Pathology Laboratory, 19180 Marchamalo, Guadalajara, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Martín-Hernández
authors.affiliation: Universidad San Pablo-CEU, Biology Department, 28668 Montepríncipe, Spain.Centro Apícola Regional, Bee Pathology Laboratory, 19180 Marchamalo, Guadalajara, Spain.
authors.forename: Mariano
authors.initials: M
authors.lastname: Higes
authors.affiliation: Universidad San Pablo-CEU, Biology Department, 28668 Montepríncipe, Spain.Centro Apícola Regional, Bee Pathology Laboratory, 19180 Marchamalo, Guadalajara, Spain.
authors.forename: Nuno
authors.initials: N
authors.lastname: Henriques-Gil
mesh_terms: D000818:Animals; D001209:Asia, Central; D001483:Base Sequence; D001516:Bees / Q000382:microbiology*; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D005060:Europe; D006239:Haplotypes; D054643:INDEL Mutation; D008969:Molecular Sequence Data; D016818:Nosema / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal