Functional Characterization of Two RNA Methyltransferase Genes and Uncovers the Roles of mA in Mediating Adaptation of to Host Plants.

-methyladenosine (mA) is one of the major epigenetic modifications in eukaryotes. Although increasing functions of mA have been identified in insects, its role in L. for host plant adaptation remains unclear. In the current study, we show that the mA content of was relatively low in different developmental stages and tissues, with no significant differences. Two RNA methyltransferase genes, (methyltransferase-like 3) and (methyltransferase-like 14), were identified and characterized. could be transcribed into two transcripts, and had only one transcript; both of these genes were highly expressed in egg and adult stages and reproductive tissues. The CRISPR/Cas9-mediated knockout of (Δ) or (Δ) confirmed their function in mA installation into RNA. Furthermore, upon transfer from an artificial diet to the host plant, the mutant strains were affected in terms of larval and pupal weight or adult emergence rate, while the wildtype (WT) strain did not exhibit any difference. In addition, the fecundity and egg hatching rate of the WT strain decreased significantly, whereas only the Δ mutant strain displayed significantly decreased fecundity. There seemed to be a tradeoff between the stress adaptation and reproduction in mediated by mA modification. During host transfer, the expression of was consistent with the change in mA content, which implied that could respond to host plant defense effectively, and may regulate mA content. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the differentially expressed transcripts with changes in mA levels revealed that the potential functions of mA-related genes may be involved in steroid biosynthesis for larval performance and metabolic pathways for adult reproduction. Overall, our work reveals an epigenetic regulation mechanism for the rapid adaptation of to variations in the host environment.