Gene-regulatory independent functions for insect DNA methylation

The function of cytosine (DNA) methylation in insects remains unknown. Using RNA interference we provide evidence for the functional role of the maintenance DNA methyltransferase 1 ( Dnmt1 ) in Oncopeltus fasciatus , a hemimetabolous insect. Individuals depleted for Dnmt1 , and subsequently DNA methylation, failed to reproduce. Depletion of DNA methylation did not result in changes in gene or transposable element expression. Eggs were inviable and declined in number, and nuclei structure of follicular epithelium was aberrant, revealing an important function of DNA methylation seemingly not contingent on gene expression. Our work provides direct experimental evidence for a functional role of Dnmt1 and DNA methylation independent of gene expression in insects.