Suppression of cytoplasmic incompatibility in the leaf-mining fly Liriomyza sativae with a nuclear Wolbachia insert

Cytoplasmic incompatibility (CI) drives maternally transmitted
endosymbionts such as Wolbachia through insect populations by inducing
embryonic mortality when infected males fertilize uninfected females. CI
is controlled by Wolbachia cif operons that are categorized into multiple
phylogenetic Types. CI strength is further shaped by poorly understood
host factors, including development and genetic background. To study the
strength of CI across different host species, we genotyped a Japanese
field population of Liriomyza sativae. By uncovering paternal transmission
of Wolbachia genic elements, we collected strong evidence of horizontal
genome transfer, including Type I and Type V cif operons, from Wolbachia
into the nuclear genome of L. sativae. We established a transinfection of
wLtri in L. sativae, a Wolbachia variant that induces strong CI in
Liriomyza trifolii. No CI was observed in both intraspecific and
interspecific reciprocal crosses with L. trifolii, suggesting that both
uninfected females and infected males of L. sativae completely suppress
wLtri-mediated CI. Our results raise the appealing hypothesis that host
suppression of Wolbachia-induced CI might evolve due to horizontal
transfer of cif operons into the host nuclear genome.