Using RNAi to silence heat shock protein has congeneric effects in North America's Dendroctonus bark beetles

Losses associated with forest pest outbreaks are increasing at an alarming rate, exacerbated by fluctuating climate patterns, and unimpeded by traditional management approaches that fail to keep pace with growing pressures. Future forest pest management strategies demand augmentation with next generation approaches. RNA interference, or RNAi, is a naturally occurring eukaryotic immune response to viral infection that works by disrupting the translation of mRNA into protein and can be manipulated to cause insect mortality through the introduction of carefully designed dsRNAs. The effective induction of the RNAi pathway depends on the exact match of a sequence at least sixteen nucleotides in length, making non-target effects unlikely. Thus, RNAi is increasingly praised as a species-specific pest management approach. The southern pine beetle (SPB), Dendroctonus frontalis, and its congener, the mountain pine beetle (MPB), D. ponderosae, are highly destructive forest pests endemic to North and Central America experiencing unprecedented range expansions, with extensive impacts on affected ecosystems. We have demonstrated that oral ingestion of specific dsRNAs induces gene silencing via RNAi and causes rapid and significant mortality in both SPB and MPB. Here we evaluate the ability of dsRNAs targeting SPB to affect gene expression in MPB, and the ability of dsRNAs targeting MPB to affect gene expression in SPB. We found that species-specific dsRNAs designed for gene silencing in one species can silence genes in the reciprocal species, offering the potential for development of RNAi as a Dendroctonus-specific management tool against rapidly expanding bark beetle populations.