What Shapes RNA Interference Responsiveness in Heteroptera (Insecta: Hemiptera)? An Evidence-Constrained Multilevel Framework for Experimental Design and Optimisation

Abstract

Simple Summary Many true bugs (Heteroptera), including several major crop pests, are difficult to control. RNA interference (RNAi) can reduce the activity of a selected gene and is useful for studying insect biology and developing selective pest-control methods. In many experiments, RNAi is effective when double-stranded RNA is injected but weaker or less predictable after feeding or application to the insect surface. We reviewed evidence for the biological processes that may explain this variation. The strongest direct evidence concerns the breakdown of double-stranded RNA outside cells, particularly in saliva and digestive fluids of selected true bugs, including Pentatomidae and Miridae. Functional silencing in tissues distant from the exposure site has also been observed, although the nature and movement of the silencing signal remain unresolved. Other proposed explanations, including restricted passage across the gut, poor cellular entry, trapping within cellular compartments, and inefficient intracellular processing, have not been demonstrated as limiting steps in true bugs. We therefore present an evidence-constrained framework for identifying processes that limit RNAi in a defined species, life stage, delivery route, tissue, and target-gene system. Comparing delivery routes and measuring intermediate steps should improve experimental interpretation and guide more reliable, species-specific pest-management approaches.