A tangled web: Origins of reproductive parasitism

Abstract

While typically a flea parasite and opportunistic human pathogen, the presence of Rickettsia felis (strain LSU-Lb) in the non-bloodfeeding, parthenogenetically reproducing booklouse, Liposcelis bostrychophila, provides a systemto ascertain factors governing not only host transitionsbut alsoobligate reproductiveparasitism (RP).Analysis of plasmidpLbAR,uniquetoR. felis str. LSU-Lb, revealed a toxin-antitoxinmodulewith similar features to prophage-encoded toxin-antitoxinmodules utilized by parasiticWolbachia strains to induce another form of RP, cytoplasmic incompatibility, in their arthropod hosts. Curiously, multiple deubiquitinase and nuclease domains of the large (3,841 aa) pLbAR toxin, aswell the entire antitoxin, facilitated the detection of an assortment of related proteins from diverse intracellular bacteria, including other reproductive parasites. Our description of these remarkable components of the intracellular mobilome, including their presence in certain arthropod genomes, lends insight on the evolution of RP, while invigorating research on parasite-mediated biocontrol of arthropod-borne viral and bacterial pathogens.