Abstract:  MicroRNAs (miRNAs) are a class of 19-24 nt endogenous non-coding small RNAs universally existing in various organisms. MiRNAs can regulate gene expression mainly by the combination between its seed region and the ORF or 3′UTR of target genes at the posttranscriptional level, and play critical roles in multiple biological processes including cell differentiation, proliferation and apoptosis. As miRNAs have eventually become a research hotspot in life sciences, great advances have been made in the study of insect miRNAs. The development of highthroughput sequencing and bioinformatics have accelerated the identification of miRNAs in different species, providing the theoretical basis for subsequent research. MiRNAs can be identified with direct cloning, bioinformatics prediction and highthroughput sequencing while their expression levels can be detected through miRNA gene chip analysis, Northern blot and realtime quantitative PCR (RT-qPCR). Inhibition of expression or overexpression of miRNAs can be applied to further reveal their biological functions. MiRNAs exert significant influence on insect growth and reproduction process by participating in ecdysone pathway and regulating the expression of some related genes such as genes related to ecdysone receptor, sex differentiation, wing development, lipid metabolism and ovarian development. MiRNAs are also involved in the circadian rhythm, memory formation and leaning capacity of some insects. In the progress of insect-virus interaction, a number of virus-encoded miRNAs disturb the immune response of host insects by regulating target gene expression while the insectencoded miRNAs influence virus replication. MiRNAs have also been found to participate in insect immune response against exogenous pathogens via regulating the expression of immunerelated genes, which affect innate immune response of insects. Additionally, it has been reported that miRNAs develop or enhance insecticide resistance by negatively regulating the expression of detoxification-related genes, altering insect susceptibility to insecticides and contributing to insecticide resistance in insects. This review provides a theoretical basis for further understanding of insect miRNAs and their potential applications in integrated pest management.

Key words: Insect, miRNA, post-transcriptional regulation, target gene, host-virus interaction