Identification and characterization of microRNAs in the immature stage of the beneficial predatory bug Arma chinensis Fallou (Hemiptera: Pentatomidae)

MicroRNAs (miRNAs) are a type of small noncoding RNAs that regulate gene expression at the posttranscriptional level and can influence significant biological processes. Arma chinensis (Hemiptera: Pentatomidae) is a predaceous insect species that preys upon a wide variety of insect pests. It is important to explore and understand the molecular mechanisms involving miRNAs in regulating developmental and other gene expression for beneficial insects. However, examination of miRNAs associated with Hemiptera, especially predatory bugs, has been absent or scarce. This study represents the first comprehensive analysis of predatory bug A. chinensis encoded miRNAs through high throughput sequencing and predicts genes and biological processes regulated by the newly identified miRNAs through analyzing their differential expression in and across five nymphal instars. A total of 64 A. chinensis miRNAs, including 46 conserved miRNAs and 18 novel miRNAs, were identified by analysis of high throughput sequence reads mapped to the genome. A total of 2913 potential gene targets for these 64 miRNAs were predicted by comprehensive analyses utilizing miRanda, PITA, and RNAhybrid. Gene Ontology annotation of predicted target genes of A. chinensis suggested the key processes regulated by miRNAs involved biological processes, regulation of cellular processes, and transporter activity. Kyoto Encyclopedia of Genes and Genomes pathway predictions included the Toll and Imd signaling pathway, Valine, leucine and isoleucine degradation, Steroid biosynthesis, the AGE-RAGE signaling pathway in diabetic complications, and Alanine, aspartate and glutamate metabolism. This newly identified miRNAs through analyzing their differential expression, assessment of their predicted functions forms a foundation for further investigation of specific miRNAs.