Transinfection of Wolbachia in planthoppers: nymphal injection of cultured Wolbachia and infection dynamics.

Wolbachia species are intracellular symbionts that cause reproductive alterations in arthropods. Transinfection experiments have been performed in many arthropod species to elucidate the interaction between Wolbachia and a new host. To ease transinfection of this bacterium to new arthropod hosts, we introduced two techniques: nymphal injection instead of embryonic injection and the use of a cultured source of Wolbachia instead of direct transfer from donors to recipients. Wolbachia in the small brown planthopper Laodelphax striatellus was cultivated in a cell line and injected into the nymphal body cavity of the brown planthopper Nilaparvata lugens together with the cells. By using these techniques, two transinfected planthopper lines were obtained. In one line, Wolbachia disappeared after several generations; in the other line, Wolbachia was retained for >7 yr. Infection rates in this latter transinfected line were approximately 80% in early generations after transinjection but decreased to <10% through 40-60 generations. Subsequent selection for Wolbachia-infected females in this line did not increase the infection rate as a temporary effect. Thus, this transinfected line of N. lugens showed cytoplasmic incompatibility, although the incompatibility level was lower than in L. striatellus, the original host. The method of transinfection presented herein is useful for transmitting intracellular symbionts between small arthropod hosts.