Functional Identification and Characterization of Leucokinin and Its Receptor in the Fall Webworm, Hyphantria cunea

Fan

Wang

et al. 2022

IJMS

RNA interference (RNAi) technology is a promising approach used in pest control. The efficiency of RNAi varies considerably among different insect species, and growing evidence suggests that degradation of double-stranded RNA (dsRNA) prior to uptake is an important factor that limits RNAi efficiency in insects. Our recent work on fall webworm (Hyphantria cunea), an important invasive pest in China, showed a relatively low silencing efficiency of RNAi through dsRNA injection, which is considered the most feasible dsRNA delivery method for inducing RNAi, and the factors involved in the mechanism remain unknown. Herein, we first detected the dsRNA-degrading activity in the hemolymph and gut content of H. cunea in ex vivo assays and observed rapid degradation of dsRNA, especially in the hemolymph, which was complete within only 10 min. To determine whether dsRNA degradation could contribute to the low effectiveness of RNAi in H. cunea, four dsRNA nuclease (dsRNase) genes, HcdsRNase1, HcdsRNase2, HcdsRNase3, and HcdsRNase4, were identified by homology searching against the H. cunea transcriptome database, and their transcript levels were subsequently investigated in different tissues, developmental stages, and after dsRNA injection. Our results show that HcdsRNases are highly expressed mainly in gut tissues and hemolymph, and the expression of HcdsRNase3 and HcdsRNase4 were significantly upregulated by dsGFP induction. RNAi-of-RNAi studies, using HcCht5 as a reporter gene, demonstrated that silencing HcdsRNase3 and HcdsRNase4 significantly increases RNAi efficacy via dsHcCht5 injection, and co-silencing these two HcdsRNase genes results in a more significant improvement in efficacy. These results confirm that the RNAi efficacy in H. cunea through dsRNA injection is certainly impaired by dsRNase activity, and that blocking HcdsRNases could potentially improve RNAi, providing a reference for related studies on insects where RNAi has low efficiency.

Section: Introductionmentioning

confidence: 99%

RNAi Efficiency through dsRNA Injection Is Enhanced by Knockdown of dsRNA Nucleases in the Fall Webworm, Hyphantria cunea (Lepidoptera: Arctiidae)

Fan

Wang

et al. 2022

IJMS

“…Hyphantria cunea (Lepidoptera: Erebidae), also known as the fall webworm, is a quarantine pest found worldwide [ 23 ]. In the past few decades, H. cunea has spread from North America to many countries in Asia, Europe, and the Americas through anthropogenic activities.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Toxic Effects of Tannic Acid Treatment on Hyphantria cunea Larvae

Tan

Yan

et al. 2022

Insects

To increase the development potential of botanical pesticides, it is necessary to expand the toxicology research on plant secondary metabolites. Herein, the Hyphantria cunea larvae were exposed to tannic acid concentrations consistent with those found in larch needles, and, subsequently, the growth and nutrient utilization, oxidative damage, and detoxification abilities in the larval midgut, as well as the changes in the gut microbiome, were analyzed. Our results revealed that tannic acid treatment significantly increased the mortality of H. cunea larvae and inhibited larval growth and food utilization. The contents of malondialdehyde and hydrogen peroxide in the larval midgut were significantly elevated in the treatment group, along with a significant decrease in the activities of antioxidant enzymes and detoxifying enzymes. However, the non-enzymatic antioxidants showed a significant increase in the tannic acid-treated larvae. From gut microbiome analysis in the treatment group, the abundance of gut microbiota related to toxin degradation and nutrient metabolism was significantly reduced, and the enrichment analysis also suggested that all pathways related to nutritional and detoxification metabolism were substantially inhibited. Taken together, tannic acid exerts toxic effects on H. cunea larvae at multiple levels and is a potential botanical pesticide for the control of H. cunea larvae.

“…The fall webworm Hyphantria cunea Drury (Lepidoptera: Arctiidae), a polyphagous insect that originally evolved in North America, is a globally important invasive pest feeding on at least 300 different plant species 1,2 . It has caused significant economic and ecological damage since it was first reported in China in 1979 3,4 . Ecologically, owing to its high fecundity and enhanced survivability, this pest is extremely competitive and a threat to biodiversity 5 .…”

Section: Introductionmentioning

confidence: 99%

Bacteria‐mediated RNAi for managing fall webworm, Hyphantria cunea: screening target genes and analyzing lethal effect

Fan

Pest Management Science

et al. 2022

Background The fall webworm, Hyphantria cunea, an invasive forest pest found worldwide, causes serious ecological and economic damage. Currently, the application of chemical pesticides is the most widely used strategy for H. cunea management. However, long‐term pesticide use leads to pest resistance, phytotoxicity, human poisoning, and environmental deterioration. RNA interference (RNAi) technology may provide an environmentally friendly and cost‐effective option for H. cunea control. However, effective RNAi targets and application methods for H. cunea are lacking. Results We screened and obtained two highly effective RNAi targets, vATPase A (V‐type proton ATPase catalytic subunit A) and Rop (Ras opposite), from 23 candidate genes, using initial and repeat screening tests with the double‐stranded RNA (dsRNA) injection method. RNAi against these two genes was effective in suppressing each target messenger RNA level and interfering with larval growth, leading to significant larval mortality and pupal abnormality. For massive production of dsRNA and practical application of RNAi technology in H. cunea, transformed bacteria expressing dsRNAs of these two genes were prepared using the L4440 expression vector and HT115 strain of Escherichia coli. Oral administration of bacterially expressed dsRNA targeting vATPase A and Rop genes showed high mortality and the same malformed phenotype as the injection treatment. To further investigate the lethal effects of targeting these two genes on larval development, transcriptome sequencing (RNA‐seq) was performed on RNAi samples. The results demonstrated disorders in multiple metabolic pathways, and the expression levels of most genes related to insect cuticle metabolism were significantly different, which may directly threaten insect survival. In addition, some new findings were obtained via RNA‐seq analysis; for example, the progesterone‐mediated oocyte maturation and oocyte meiosis processes were significantly different after silencing vATPase A, and the insect olfactory protein‐related genes were significantly downregulated after dsHcRop treatment. Conclusion vATPase A and Rop are two highly effective RNAi‐mediated lethal genes in H. cunea that regulate insect growth via multiple metabolic pathways. Oral delivery of bacterially expressed dsRNA specific to vATPase A and Rop can potentially be used for RNAi‐based H. cunea management. This is the first study to apply bacteria‐mediated RNAi for the control of this invasive pest, which is a major step forward in the application of the RNAi technology in H. cunea. © 2022 Society of Chemical Industry.