MiR-3017b contributes to metamorphosis by targeting sarco/endoplasmic reticulum Ca2+ ATPase in Tribolium castaneum

In recent years, increasing numbers of microRNAs (miRNAs) have been reported to regulate insect metamorphosis. One thousand, one hundred fifty-four miRNAs have been previously identified from Tribolium castaneum by high-throughput sequencing; however, little is known about which miRNAs can participate in metamorphosis, leaving the role of miRNAs in regulating the underlying mechanism elusive. Here, we report the participation of miR-3017b in the metamorphosis of T. castaneum. Temporal profiles revealed that miR-3017b was highly expressed at the late larval stage, but significantly decreased at the early pupal stage. Overexpression of miR-3017b caused larval to pupal to adult metamorphosis arrested. Dual-luciferase reporter assay and miRNA-mRNA interaction assay illustrated that miR-3017b interacts with the coding sequence of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) and suppresses its expression. Knockdown of SERCA caused metamorphosis arrested, similar to that observed in miR-3017b overexpression beetles. Further functional mechanism analyses revealed that 20-hydroxyecdysone application downregulates miR-3017b and up-regulates SERCA expression. The expression level of downstream genes in the 20E pathway was disrupted after overexpressing miR-3017 and the knockdown of SERCA. These results provided evidence miR-3017b-SERCA contributes to metamorphosis by regulating the 20E pathway in T. castaneum. It could advance our understanding of the coordination of 20E and miRNA regulation in insect metamorphosis.