CryomiRs: Characterization of a cold-associated family of microRNAs in E. solidaginis and E. scudderiana

Cold-hardy insect larvae, such as the freeze-tolerant Eurosta solidaginis and the freeze-avoiding Epiblema scudderiana, have the ability to endure significant sub-zero temperatures during the winter months. While not unique, this ability is rare and requires exceptional physiological and molecular adaptations. Both overwintering strategies exhibit similarities, such as an entrance into a deep hypometabolic state characterized by substantial modulation of protein translation.  Differences do however exist, with E. solidaginis larvae overcoming the stress via extracellular ice formation and E. scudderiana avoiding ice formation altogether by producing high concentrations of carbohydrate cryoprotectants. We hypothesize that microRNAs (miRNAs), small RNA molecules capable of inhibiting mRNA translation, could play a role in the overwintering survival of cold-hardy insect larvae. To test this hypothesis, RNA from cold-stressed and control E. solidaginis and E. scudderiana larvae was isolated and then followed by Ion Torrent high throughput miRNA sequencing. Differential expression of a small sub-set of miRNAs, referred to as “CryomiRs”, was notably observed between the two species suggesting a common signature of miRNAs underlying insect cold adaptation.  Validation of this signature in additional natural models of hypometabolism, including mammalian hibernation, is currently underway.