Double-stranded RNA Oral Delivery Methods to Induce RNA Interference in Phloem and Plant-sap-feeding Hemipteran Insects

Abstract

Phloem and plant sap feeding insects invade the integrity of crops and fruits to retrieve nutrients, in the process damaging food crops. Hemipteran insects account for a number of economically substantial pests of plants that cause damage to crops by feeding on phloem sap. The brown marmorated stink bug (BMSB), Halyomorpha halys (Heteroptera: Pentatomidae) and the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae) are hemipteran insect pests introduced in North America, where they are an invasive agricultural pest of high-value specialty, row, and staple crops and citrus fruits, as well as a nuisance pest when they aggregate indoors. Insecticide resistance in many species has led to the development of alternate methods of pest management strategies. Double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) is a gene silencing mechanism for functional genomic studies that has potential applications as a tool for the management of insect pests. Exogenously synthesized dsRNA or small interfering RNA (siRNA) can trigger highly efficient gene silencing through the degradation of endogenous RNA, which is homologous to that presented. Effective and environmental use of RNAi as molecular biopesticides for biocontrol of hemipteran insects requires the in vivo delivery of dsRNAs through feeding. Here we demonstrate methods for delivery of dsRNA to insects: loading of dsRNA into green beans by immersion, and absorbing of gene-specific dsRNA with oral delivery through ingestion. We have also outlined non-transgenic plant delivery approaches using foliar sprays, root drench, trunk injections as well as clay granules, all of which may be essential for sustained release of dsRNA. Efficient delivery by orally ingested dsRNA was confirmed as an effective dosage to induce a significant decrease in expression of targeted genes, such as juvenile hormone acid O-methyltransferase (JHAMT) and vitellogenin (Vg). These innovative methods represent strategies for delivery of dsRNA to use in crop protection and overcome environmental challenges for pest management.

Prospects, challenges and current status of RNAi through insect feeding

“…Targeting insects that feed internally (sap sucking and endophagous insects) with synthetic dsRNA requires a different strategy because spraying dsRNA solutionsx2 on plant surfaces is not effective against these species. A recent study used the plant vascular system to deliver dsRNA solutions via soil irrigation and trunk injection to target the sap‐sucking brown marmorated stink bug . The irrigation and trunk injection of the vitellogenin‐A1 and juvenile hormone acid O‐methyltransferase dsRNAs showed 35–40% mortality in brown marmorated stink bugs .…”

“…66,67 The irrigation and trunk injection of the vitellogenin-A1 and juvenile hormone acid O-methyltransferase dsRNAs showed 35-40% mortality in brown marmorated stink bugs. 66,67 Similarly, a study was published on Tuta absoluta, an insect that feeds as a leafminer. The plant roots were immersed into ryanodine receptors (RyRs), acetylcholinesterase (AChE), and nicotinic acetylcholine alpha 6 (nAChRs) dsRNA solutions.…”

Identification and characterization of capa and pyrokinin genes in the brown marmorated stink bug, Halyomorpha halys (Hemiptera): Gene structure, immunocytochemistry, and differential expression

“…The spread of BMSB populations is threatening a wide range of economic crops (Leskey & Nielsen, ). It has spurred to develop various management options including pheromone‐based monitoring and trapping (Khrimian et al, ), biological control utilizing entomopathogenic fungi (Gouli et al, ), and a recent RNA interference (RNAi)‐mediated approach (Ghosh, Hunter, Park, & Gundersen‐Rindal, , ).…”

BAPC-assistedCRISPR/Cas9 System: Targeted Delivery into Adult Ovaries for Heritable Germline Gene Editing (Arthropoda: Hemiptera)

“…Advances in biotechnologies, like CRISPR and RNAi provides new sustainable and environmentally friendly strategies to reduce insect vectors, like psyllids (Andrade & Hunter 2016; 2017; Hunter & Sinisterra-Hunter 2018; Taning et al, 2016; Ghosh et al, 2018). These advances will also aid in the management of many other insect vectors and pests (Chaverra-Rodriguez et al, 2018; Darrington et al, 2017; Dong, et al, 2015; 2018; Gantz & Akbari 2018; Ghosh et al, 2018; Kolliopoulou et al, 2017; Sinisterra-Hunter & Hunter 2018; Taning et al, 2017; Zotti et al, 2018).…”