Identification, Characterization and Expression Profiling of Micrornas in Spodoptera frugiperda after Challenge with Soybean Peptidase Inhibitors

MicroRNAs (miRNAs) represent a major class of posttranscriptional regulators, which play key roles in biological and physiological processes. In the current study, we characterized miRNAs from the fall armyworm, Spodoptera frugiperda, one of the major Lepidoptera pest. The RNA was extracted from the fall armyworm midgut reared in artificial diet with or without soybean peptidase inhibitors (SPIs). Using small RNA sequencing, a total of 136 miRNAs were predicted, including 63 novel miRNAs and 73 newly miRNAs homologs to known miRNAs in other species. Out of the newly described miRNAs, 13 were homologs of other insect species and 37 were specifically similar to Bombyx mori (Lepidoptera). In addition, we used RT-qPCR analysis to validate the expression of five novel and five conserved miRNAs. These miRNAs regulate mainly mRNAs related to metabolic process and catalytic activity. We obtained significantly different expression between miRNAs from larvae midgut reared on an artificial diet with and without soybean peptidase inhibitors (SPIs). We identified 20 miRNAs that were expressed only in larvae feed with SPI. These miRNAs probably are involved at signaling cascade of serine peptidases response from S. frugiperda to the SPI ingestion.