title: An endosymbiotic bacterium in a plant-parasitic nematode: member of a new Wolbachia supergroup.
abstract: Wolbachia is an endosymbiotic bacterium widely present in arthropods and animal-parasitic nematodes. Despite previous efforts, it has never been identified in plant-parasitic nematodes. Random sequencing of genes expressed by the burrowing nematode Radopholus similis resulted in several sequences with similarity to Wolbachia genes. The presence of a Wolbachia-like endosymbiont in this plant-parasitic nematode was investigated using both morphological and molecular approaches. Transmission electronmicroscopy, fluorescent immunolocalisation and staining with DAPI confirmed the presence of the endosymbiont within the reproductive tract of female adults. 16S rDNA, ftsZ and groEL gene sequences showed that the endosymbiont of R. similis is distantly related to the known Wolbachia supergroups. Finally, based on our initial success in finding sequences of this endosymbiont by screening an expressed sequence tag (EST) dataset, all nematode ESTs were mined for Wolbachia-like sequences. Although the retained sequences belonged to six different nematode species, R. similis was the only plant-parasitic nematode with traces of Wolbachia. Based on our phylogenetic study and the current literature we designate the endosymbiont of R. similis to a new supergroup (supergroup I) rather than considering it as a new species. Although its role remains unknown, the endosymbiont was found in all individuals tested, pointing towards an essential function of the bacteria.
authors.affiliation: Department of Molecular Biotechnology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Haegeman
authors.forename: Bartel
authors.initials: B
authors.lastname: Vanholme
authors.forename: Joachim
authors.initials: J
authors.lastname: Jacob
authors.forename: Tom T M
authors.initials: TT
authors.lastname: Vandekerckhove
authors.forename: Myriam
authors.initials: M
authors.lastname: Claeys
authors.forename: Gaetan
authors.initials: G
authors.lastname: Borgonie
authors.forename: Godelieve
authors.initials: G
authors.lastname: Gheysen
mesh_terms: D000818:Animals; D001181:Arthropods / Q000235:genetics* / Q000469:parasitology; D020869:Gene Expression Profiling; D017238:Genes, Helminth / Q000235:genetics*; D006790:Host-Parasite Interactions; D008969:Molecular Sequence Data; D009348:Nematoda / Q000235:genetics*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics*; D020577:Wolbachia / Q000145:classification / Q000235:genetics*