Evolution of m6A related genes in insects and function of METTL3 in embryonic development of silkworm.

N6-methyladenosine (m6A), the most prevalent modification in eukaryotic RNAs, plays a key role in biological processes. However, the evolutionary relationships and function of m6A related genes in insects are still largely unknown. Here, we analyzed the phylogenetics of m6A related genes among 204 insects and find that m6A related genes are evolutionarily conserved in insects. We apply the lepidopteran model insect Bombyx. mori as a study system. Subcellular localization experiments in BmN cells confirmed that YTHDF3 localizes in the cytoplasm, METTL3, METTL14 and YTHDC localize in the nucleus, while FL2D localizes in both nucleus and cytoplasm. We also detected expression pattern of m6A related genes during the embryonic development of B. mori. To elucidate the function of METTL3 during embryonic stage, RNA sequencing was performed to measure differential expressions of mRNA from silkworm eggs after METTL3 knockdown. The global transcriptional pattern showed that the physiological responses induced by METTL3 knockdown involved multiple cellular processes, including oxidoreductase activity, transcription regulator activity, cation binding and other fundamental physiological processes. Many metabolism processes, such as carbon metabolism, purine metabolism, biosynthesis of amino acids, and the citrate cycle, were partially affected. Furthermore, METTL3 knockdown significantly activated Wnt and Toll/Imd pathways in embryonic stage. The results suggest that METTL3 plays an important role during the embryonic development of B. mori. This study deepens our understanding of the function of m6A related genes in insects.