MicroRNA miR-285 modulates the metamorphosis in Galeruca daurica by targeting Br-C.

BACKGROUD: Galeruca daurica has become a new pest on the Inner Mongolia grasslands since its abrupt outbreak in 2009, and caused serious damage. As a pupa indicator during insect metamorphosis, the early response gene of ecdysone signaling pathway, Broad-Complex (Br-C), plays a vital role in the growth and development of insects. MicroRNAs (miRNA) are small non-coding RNAs which mediate various biological activities. However, it is unknown whether and how Br-C is regulated by miRNAs.

RESULTS: Temporal expression profiles revealed that miR-285 and Br-C basically displayed an opposite trend during the larval-adult development, and Br-C was sharply up-regulated on the last day of final instar larvae meanwhile miR-285 was significantly down-regulated. Both dual-luciferase reporter assay and miRNA-mRNA interaction assay indicated that miR-285 interacts with the coding sequence of Br-C and represses its expression. Not only overexpression but also downexpression of miR-285 led to the failure of larval to pupal to adult metamorphosis. In addition, both overexpression of miR-285 and silence of Br-C inhibited the expression of Br-C and other ecdysone signaling pathway genes including E74, E75, ECR, FTZ-F1, and HR3. On the contrary, suppressing miR-285 obtained opposite results. Further experiments showed that 20-hydroxyecdysone down-regulated miR-285, and up-regulated Br-C and above-mentioned genes whereas JHA resulted in opposite effects.

CONCLUSION: Our results reveal that miR-285 is involved in mediating the metamorphosis in G. daurica by targeting Br-C in the ecdysone signaling pathway. miR-285 and its target Br-C could be as a potential target for G. daurica management.