RNA interference (RNAi) for selective gene silencing in Astigmatid mites

Psoroptic mange, caused by the Astigmatid mite Psoroptes ovis, is an ectoparasitic disease of significant economic importance to agriculture on a global scale and poses a serious welfare concern. With the current chemotherapeutic controls considered unsustainable, there is pressing need for novel control strategies. RNA interference has been proposed as a potential high throughput approach for the identification of novel therapeutic targets with high specificity, speed and at a relatively low cost compared to the existing methods. The presence of the components of the RNA interference (RNAi) pathway in P. ovis was first confirmed through in silico analyses of the P. ovis transcriptome and, following development of a non-invasive immersion method of double stranded RNA (dsRNA) delivery, gene silencing by RNAi was demonstrated in P. ovis. Statistically-significant reduction of transcript level was measured for the three genes targeted: P. ovis mite group 2 allergen (Pso o 2), P. ovis mu class glutathione S-transferase (PoGST-mu1) and P. ovis beta tubulin (Poβtub). This is the first demonstration of gene silencing by RNAi in P. ovis and provides a key mechanism for mining transcriptomic and genomic datasets in the future for novel targets of intervention against P. ovis. The first assessment of gene silencing was also performed in two related Astigmatid mites of high medical importance; the European house dust mite Dermatophagoides pteronyssinus and the scabies mite Sarcoptes scabiei. A statistically-significant reduction in expression of a D. pteronyssinus mu class glutathione S-transferase (DpGST-mu1) transcript was observed. No significant reduction in expression of a S. scabiei mu class glutathione S-transferase (SsGST-mu1) transcript was observed. Additionally, microRNAs (miRNAs) from the related miRNA pathway were identified in a P. ovis small RNA sample and were sequenced and annotated