Abstract
BackgroundThe function of cytosine (DNA) methylation in insects remains inconclusive due to a lack of mutant and/or genetic studies.ResultsHere, we provide evidence for the functional role of the maintenance DNA methyltransferase 1 (Dnmt1) in an insect using experimental manipulation. Through RNA interference (RNAi), we successfully posttranscriptionally knocked down Dnmt1 in ovarian tissue of the hemipteran Oncopeltus fasciatus (the large milkweed bug). Individuals depleted for Dnmt1, and subsequently DNA methylation, failed to reproduce. Eggs were inviable and declined in number, and nuclei structure of follicular epithelium was aberrant. Erasure of DNA methylation from gene or transposon element bodies did not reveal a direct causal link to steady-state mRNA levels in somatic cells. These results reveal an important function of Dnmt1 seemingly not contingent on directly controlling gene expression.ConclusionsThis study provides direct experimental evidence for a functional role of Dnmt1 in egg production and embryo viability and uncovers a trivial role, if any, for DNA methylation in control of gene expression in O. fasciatus.
Highlights
The function of cytosine (DNA) methylation in insects remains inconclusive due to a lack of mutant and/or genetic studies
Despite finding levels of methylated CG within coding regions reduced by 83.55%, we found no evidence for DNA methylation directly affecting transcription in the cells examined
Our results suggest DNA methyltransferase 1 (Dnmt1) is required for reproduction in O. fasciatus that is likely mediated by a gene-regulatory independent function
Summary
The function of cytosine (DNA) methylation in insects remains inconclusive due to a lack of mutant and/or genetic studies. DNA methylation in insects has been hypothesized to play numerous functional roles including polyphenism, diapause, longevity, and social behavior and caste differentiation [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. Dnmt might be necessary for development and embryonic viability in insects, but the functional contribution of DNA methylation is unknown [25]
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