Suppressing tawny crazy ant (Nylanderia fulva) by RNAi technology

Abstract

The tawny crazy ant (Nylanderia fulva) is a new invasive pest in the United States. At present, its management mainly relies on the use of synthetic insecticides, which are generally ineffective at producing lasting control of the pest, necessitating alternative environmentally friendly measures. In this study, we evaluated the feasibility of gene silencing to control this ant species. Six housekeeping genes encoding actin (NfActin), coatomer subunit β (NfCOPβ), arginine kinase (NfArgK), and V-type proton ATPase subunits A (NfvATPaseA), B (NfvATPaseB) and E (NfvATPaseE) were cloned. Phylogenetic analysis revealed high sequence similarity to homologs from other ant species, particularly the Florida carpenter ant (Camponotus floridanus). To silence these genes, vector L4440 was used to generate six specific RNAi constructs for bacterial expression. Heat-inactivated, dsRNA-expressing Escherichia coli were incorporated into artificial diet. Worker ants exhibited reduced endogenous gene expression after feeding on such diet for 9 d. However, only ingestion of dsRNAs of NfCOPβ (a gene involved in protein trafficking) and NfArgK (a cellular energy reserve regulatory gene in invertebrates) caused modest but significantly higher ant mortality than the control. These results suggest that bacterially expressed dsRNA can be orally delivered to ant cells as a mean to target its vulnerabilities. Improved efficacy is necessary for the RNAi-based approach to be useful in tawny crazy ant management.

Cloning and Functional Characterization of a Double-Stranded RNA-Degrading Nuclease in the Tawny Crazy Ant (Nylanderia fulva)

“…While coleopterans are very susceptible to ingested dsRNA, lower RNAi efficiency has been observed in lepidopterans and hemipterans (Baum and Roberts, 2014). Our previous work showed rather modest effects of RNAi via dsRNA feeding in N. fulva (Meng et al, 2020). Of all house-keeping genes we selected, none exceeded 40% reduction (Meng et al, 2020).…”

“…Tawny crazy ant (N. fulva) colonies were collected from College Station, Texas, United States and maintained in an environmentally controlled room (27 • C, 80% RH) following procedures reported previously with minor modifications (Meng et al, 2020). Colonies were reared in clear 32-L plastic storage bins with a lid, the vertical sides of which were coated with Fluon to prevent ants from escaping.…”

“…Our previous work showed rather modest effects of RNAi via dsRNA feeding in N. fulva (Meng et al, 2020). Of all house-keeping genes we selected, none exceeded 40% reduction (Meng et al, 2020). Low potency is an obstacle in applying RNAi to management of N. fulva populations.…”

Alternative Methods of Ant (Hymenoptera: Formicidae) Control with Emphasis on the Argentine Ant, Linepithema humile

“…Several researchers have injected dsRNA into ant pests and documented negative effects, but injecting RNA into insects is not viable for pest ant management. The two studies that have addressed potentially more viable options by introducing sugar-based RNAi diets to ants had limited results but provide proof of concept [ 69 , 70 ]. In his PhD dissertation work, Welzel introduced dsRNA of ADP, ATP carrier protein 2 in sugar water to groups of 10 Argentine ant workers [ 69 ].…”

“…This is a first step to determine if the technology works in Argentine ants but falls short of demonstrating effects on an entire colony. Double-stranded RNAi of six housekeeping genes produced through bacterial gene expressions was incorporated into a glucose agar diet and fed to groups of 30 Nylanderia fulva, the tawny crazy ant, workers [ 70 ]. Reduced gene expression was noted for all six genes; however, survival was only significantly reduced by inhibition of two of these genes and then only by 15%.…”