Double-Stranded DNA Reduces dsRNA Degradation in the Saliva and Significantly Enhanced RNAi-Mediated Gene Silencing in Halyomorpha halys

The invasive pest Halyomorpha halys (Hemiptera: Pentatomidae) poses a significant threat to agriculture and requires control methods beyond chemical pesticides. This study investigates RNA interference (RNAi) as a targeted gene silencing approach to manage H. halys populations. However, RNAi efficacy varies between insect orders, including hemipterans, due to factors such as the rapid degradation of double-stranded RNA (dsRNA) by a DNA/RNA non-specific nuclease (HhNSE) present in the saliva of H. halys. Notably, this study proves that double-stranded DNA (dsDNA) can stabilise dsRNA in saliva, probably by competitively inhibiting HhNSE, which is highly expressed in salivary glands. In vivo tests targeting the clathrin heavy chain gene (HhCHC) demonstrate that a mixture of dsRNA-CHC and dsDNA result in enhanced gene silencing when fed to H. halys, compared to dsRNA alone. While dsRNA-CHC injection causes almost complete mortality, the dsDNA formulation do not significantly increase mortality when fed together with dsRNA-CHC. These findings highlight the need to further investigate factors beyond nucleases such as dsRNA uptake and release mechanisms in the insect gut. Nevertheless, this study provides promising insights for improving RNAi delivery in H. halys, and perhaps other pests with such nucleases, in support of sustainable pest management solutions.