Host plant genotypes affect miRNA gene expression in Hessian fly larvae

MicroRNAs (miRNAs) are small noncoding RNAs that play critical roles in regulating post transcriptional gene expression. Gall midges encompass a large group of insects that are of economic importance and also possess fascinating biological traits. The gall midge Mayetiola destructor, commonly known as the Hessian fly, is a model organism for studying gall midge biology and insect – host plant interactions. In this study, we systematically analyzed miRNAs from the Hessian fly. Deep-sequencing a Hessian fly larval transcriptome led to the identification of 89 miRNA species that are either identical or very similar to known miRNAs from other insects, and 184 novel miRNAs that have not been reported from other species. Microarray analyses revealed the expression of miRNA genes was strictly regulated during Hessian fly larval development and abundance of many miRNA genes were affected by host genotypes. The identification of a large number of miRNAs for the first time from a gall midge provides a foundation for further studies of miRNA functions in gall midge biology and behavior. Two wheat lines “Molly” and “Newton” were used in the experiment. Newton is a susceptible winter wheat that contains no Hessian fly R gene, and Molly is a nearly isogenic line of Newton, but contains the R gene H13. Larvae were collected one and three days after egg hatch from susceptible Newton and resistant Molly plants. Total RNA extracted from the collected larvae was used for microarray analysis. Three biological replications were used for each treatment and at each time point.