An association between Dnmt1 and Wnt in the production of oocytes in the whitefly Bemisia tabaci

The function of DNA methylation in insects and the DNA methyltransferase (Dnmt) genes that influence methylation remains uncertain. We used RNA interference to reduce the gene expression of Dnmt1 within the whitefly Bemisia tabaci (Hemiptera:Aleyrodidae; Gennadius), a hemipteran species that relies on Dnmt1 for proper gametogenesis. We then used RNA-seq to test an a priori hypothesis that meiosis-related genetic pathways would be perturbed. We generally did not find an overall effect on meiosis-related pathways. However, we found that genes in the Wnt pathway, genes associated with the entry into meiosis in vertebrates, were differentially expressed. Our results are consistent with Dnmt1 knockdown influencing specific pathways and not causing general transcriptional response. This is a finding that is also seen with other insect species. We also characterised the methylome of B. tabaci and assessed the influence of Dnmt1 knockdown on cytosine methylation. This species has methylome characteristics comparable to other hemipterans regarding overall level, enrichment within gene bodies, and a bimodal distribution of methylated/non-methylated genes. Very little differential methylation was observed, and difference in methylation were not associated with differences in gene expression. The effect on Wnt presents an interesting new candidate pathway for future studies.