Transfection ofWolbachiain Lepidoptera: the feminizer of the adzuki bean borerOstrinia scapulaliscauses male killing in the Mediterranean flour mothEphestia kuehniella

Abstract

Two species of Lepidoptera, Ostrinia scapulalis and Ephestia kuehniella, harbour Wolbachia, which are maternally transmitted intracellular bacteria that often cause reproductive abnormalities in arthropods. While the infection in O. scapulalis causes conversion of genetic males into functional females (feminization), that in E. kuehniella induces cytoplasmic incompatibility. In the present study, we investigated the relative importance of host and Wolbachia factors in the di¡erential expression of reproductive alterations in these insects. We transferred the Wolbachia harboured by O. scapulalis to E. kuehniella in which the original infection had been cured by tetracycline treatment. The transfected strain of E. kuehniella expressed a maternally inherited, female-biased sex ratio. Unexpectedly, two lines of evidence suggested that the sex ratio distortion was due to male killing. First, higher mortality of young larvae was observed. Second, the removal of the transferred Wolbachia resulted in the recovery of a 1:1 sex ratio, whereas the removal of a feminizer should result in a male-biased sex ratio among o¡spring. To the authors' knowledge, this is the ¢rst report that a single Wolbachia strain can cause two distinct sexual abnormalities in di¡erent hosts. Our observations highlighted the importance of host^Wolbachia interactions in determining the phenotype of reproductive alterations.

Intra-Individual Coexistence of a Wolbachia Strain Required for Host Oogenesis With Two Strains Inducing Cytoplasmic Incompatibility in the Wasp Asobara Tabida

“…However, the contribution of host and bacterial factors responsible for this diversity of phenotypes remains controversial, with some results supporting involvement of host factors (Fujii et al 2001;Sasaki et al 2002) and other results supporting involvement of bacterial factors only (Moret et al 2001). Clearly the nature of the Wolbachia-induced phenotype more likely depends both on host and bacterial factors and on the interaction between them.…”

Controversial patterns of Wolbachia infestation in the social parasitic Maculinea butterflies (Lepidoptera: Lycaenidae)

“…The establishment of the Wolbachia" effects on the hosts strongly requires experimental confirmation since one particular strain may cause the same (Dyson et al 2002) or different (Fujii et al 2001) reproductive alterations in different hosts. Namely, the phenotype seems to be dependent on interactions between the bacteria and the genomic make-up of the individual host.…”

Symbiosis And The Origin Of Species

“…The most common effect described in these studies is a change in CI level and bacterial densities when the Wolbachia are in a foreign genetic background (Boyle et al, 1993;Bordenstein and Werren, 1998;McGraw et al, 2001;Poinsot and Merçot, 2001). Other Wolbachia-host genotypic interactions include rescue of a Drosophila lethal mutation (Karr, 2000) and a phenotypic switch from feminization to male killing when a Wolbachia strain is experimentally transferred from one Lepidopteran species to another (Fujii et al, 2001).…”