Official websites use. Share sensitive information only on official, secure websites. Correspondence: hunanfengmin Of the three pathways, piRNAs and Piwi proteins appear to have the most complex biogenesis and functional roles. Significant progress has recently occurred in the understanding of the piRNA pathway in three major research areas, i. Thus, it is timely to provide an overview of the knowledge accumulated so far.
Studies in other insects are lagging behind but are highly anticipated since piRNAs and Piwi proteins are abundantly expressed not only in the germline but also in the somatic tissues. Due to the diversification of Piwi genes among insects, novel functions of piRNAs and Piwi proteins can be expected in the different species. This comprehensive review aimed to provide important background information about the current knowledge on piRNAs and Piwi proteins in insects that can function as a resource for future research.
Research on Piwi proteins and piRNAs in insects has focused on three experimental models: oogenesis and spermatogenesis in Drosophila melanogaster , the antiviral response in Aedes mosquitoes and the molecular analysis of primary and secondary piRNA biogenesis in Bombyx mori -derived BmN4 cells.
Significant unique and complementary information has been acquired and has led to a greater appreciation of the complexity of piRNA biogenesis and Piwi protein function.
Studies performed in other insect species are emerging and promise to add to the current state of the art on the roles of piRNAs and Piwi proteins. Although the primary role of the piRNA pathway is genome defense against transposons, particularly in the germline, recent findings also indicate an expansion of its functions.
