M6A writer gene fl(2)d regulates the metamorphosis of silkworm Bombyx mori

Abstract

The N6-methyladenosine (m6A) is one of the most abundant posttranscriptional modifications on RNAs, which is mediated by its effector proteins—writers, readers, and erasers. Female-Lethal(2)D (Fl(2)d) is one of the key writers to stabilize the interaction between another two writers Methyltransferase-like 3 (METTL3) and Methyltransferase-like 14 (METTL14). Here with dsRNA transfection, fl(2)d was knocked down in the BmN4 cell lines of silkworm, the expression of 61 genes were significantly increased, and 86 genes were significantly decreased after fl(2)d repression, which encoded proteins related to catalytic, hydrolase activity or in metabolism of nucleic acid. To elucidate the functional role of fl(2)d during silkworm development, dsRNA of which was injected into the hemolymph of the 2-d-old fourth instar larvae, the mounting process of silkworm was delayed, the expression level of genes in metabolism, RNA processing and ecdysone signaling pathway decreased significantly after fl(2)d knockdown, such as genes encoded Ubiquitin protein ligase E3C, the nuclear pore complex protein Nup98-Nup96, and the m6A reader YTHDF3, as well as Broad Complex isoform 2 (BRC-Z2), Fushi Tarazu Factor-1 (FTZ-F1), lactate dehydrogenase (LDH) and the ecdysone-induced protein 74EF isoform A (E74A). Total m6A level of RNAs also decreased after fl(2)d repression. These indicated that decreased level of fl(2)d and YTHDF3 decay the m6A level and translation of their target genes, which might lead to the retardation of metamorphosis, and resulted in the delayed mounting of silkworm.