Unravelling the Wolbachia evolutionary role: the reprogramming of the host genomic imprinting.

Environmental factors can play a significant role in inducing epigenetic changes that may also be inherited by future generations. The maternally-inherited symbiont of arthropods Wolbachia pipientis is an excellent candidate as an “environmental” factor promoting trans-generational epigenetic changes. Indeed, by establishing intimate relationships with germ line cells, epigenetic effects of Wolbachia symbiosis would be manifested as a “maternal effect”, in which infection of the mother modulates the offspring phenotype. In the leafhopper Zyginidia pullula, Wolbachia feminizes genetic males, leaving them as intersexes possessing phenotypic features that are typical of females (including ovaries) with the exception of male chitinous structures that are present in the last abdominal segments. Analysis of the methylation pattern revealed that genome imprinting of feminized males is identical to the female one indicating that Wolbachia may alter the proper establishment of the imprinting in the infected leafhoppers disrupting male imprinting, which dramatically influences the expression of genes involved in sex differentiation and development. Strikingly, Wolbachia is capable of inducing trans-generational inherited modification in the imprinting of the host genome.