MiRNA Omics Reveal the Mechanisms of the Dual Effects of Selenium Supplementation on the Development of the Silkworm (Bombyx mori)

This study explores the dual effects of selenium (Se) supplementation on silkworm development by analyzing miRNA expression profiles of fat bodies in silkworms under different Se concentrations (50 µM and 200 µM). Compared to the control, 84 miRNAs displayed different expression levels in the F_50 µM group, with 72 miRNAs up-regulated and 12 down-regulated; 152 miRNAs were differentially expressed in the F_200 µM group, with 124 up-regulated and 28 down-regulated. In the F_50 µM group, the target genes of differentially expressed miRNAs were mainly enriched in Toll and Imd signaling pathways, oxidative phosphorylation, and ribosome biogenesis in eukaryotes; however, mainly oxidative phosphorylation, ribosome biogenesis in eukaryotes, and the spliceosome were enriched in the F_200 µM group. Based on the results of the protein-protein interaction network and miRNA-target network, bmo-miR-2a-1-5p and bmo-miR-317-3p_L-2R+2 were screened as key miRNAs in the F_50 µM group and the F_200 µM group, respectively. The bmo-miR-2a-1-5p mainly targeted 10014128 (<i>DREDD</i>), 100862750 (<i>ATF2</i>), and 101744000 (<i>Tak1</i>) genes, which were enriched in Toll and Imd signaling pathways. The bmo-miR-317-3p_L-2R+2 primarily regulated 101738508 (<i>SF3b</i>) and 101746688 (<i>Prp19</i>) genes, which were in the spliceosome pathway. Thus, our results demonstrated that Se supplementation improved the silkworm development via bmo-miR-2a-1-5p miRNA regulation of the Toll and Imd signaling pathways and inhibited it via bmo-miR-317-3p_L-2R+2 miRNA targeting the spliceosome pathway. Our data revealed that 50 µM Se supplementation could improve silkworm productivity; meanwhile, a 200 µM Se treatment displayed toxic effects, leading to impaired development.