Unravelling the Wolbachia evolutionary role: the reprogramming of the host genomic imprinting.
Environmental factors can induce significant 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: 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. With the exception of male chitinous structures that are present in the last abdominal segment, feminized males display phenotypic features that are typical of females. These include ovaries that range from a typical histological architecture to an altered structure. Methylation-sensitive random amplification of polymorphic DNA profiles show that they possess a female genomic imprint. On the other hand, some rare feminized males bear testes instead of ovaries. These specimens possess a Wolbachia density approximately four orders of magnitude lower than feminized males with ovaries and maintain a male genome-methylation pattern. Our results indicate that Wolbachia infection disrupts male imprinting, which dramatically influences the expression of genes involved in sex differentiation and development, and the alteration occurs only if Wolbachia exceeds a density threshold. Thus, a new Wolbachia's role as an environmental evolutionary force, inducing epigenetic trans-generational changes, should now be considered.
Di.Va.P.R.A.-Entomology and Zoology Applied to the Environment, University of Turin, Via Leonardo da Vinci 44, 10095 Grugliasco (Turin), Italy. ilaria.negri@unito.it
Ilaria
I
Negri
Antonella
A
Franchini
Elena
E
Gonella
Daniele
D
Daffonchio
Peter John
PJ
Mazzoglio
Mauro
M
Mandrioli
Alberto
A
Alma
D000818:Animals; D005075:Biological Evolution; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D049750:Genome, Insect; D018392:Genomic Imprinting; D006430:Hemiptera / Q000033:anatomy & histology / Q000382:microbiology*; D008297:Male; D019849:Sex Determination Processes; D013559:Symbiosis; D020577:Wolbachia / Q000502:physiology*