Fluorescent Nanoparticle-RNAi-Mediated Silencing of Sterol Carrier Protein-2 Gene Expression Suppresses the Growth, Development, and Reproduction of Helicoverpa armigera

Abstract

Helicoverpa armigera is a polyphagous destructive lepidopteran pest with strong Bacillus thuringiensis (Bt) resistance. Cholesterol, a vital component for insect growth, can only be obtained from food, and its transfer and metabolism are regulated by sterol carrier protein-2 (SCP-2). This study examined whether H. armigera SCP-2 (HaSCP-2) gene expression, involved in cholesterol absorption, can be silenced by nanocarrier fluorescent nanoparticle-RNA interference (FNP-RNAi) by larval feeding and whether the silencing affected H. armigera development. Fluorescence microscopy showed that nanoparticle-siRNA was distributed in Ha cells and the larval midgut. FNP-HaSCP-2 siRNA suppressed HaSCP-2 expression by 52.5% in H.armigera Ha cells. FNP can effectively help deliver siRNA into cells, protect siRNA, and is not affected by serum. FNP-siRNA in vivo biological assays showed that HaSCP-2 transcript levels were inhibited by 70.19%, 68.16%, and 67.66% in 3rd, 4th, and 5th instar larvae, leading to a decrease in the cholesterol level in the larval and prepupal fatbodies. The pupation rate and adult emergence were reduced to 26.0% and 56.52%, respectively. This study demonstrated that FNP could deliver siRNA to cells and improve siRNA knockdown efficiency. HaSCP-2 knockdown by FNP-siRNA in vivo hindered H. armigera growth and development. FNP could enhance RNAi efficiency to achieve pest control by SCP-2-targeted FNP-RNAi.

Nanoparticle-Shielded dsRNA Delivery for Enhancing RNAi Efficiency in Cotton Spotted Bollworm Earias vittella (Lepidoptera: Nolidae)

“…The RNAi in lepidopterans with naked dsRNA has been a debatable issue and many studies have documented a poor RNAi response in various insects belonging to this order. However, nanoparticle intervention coupled with higher concentrations of dsRNA might be contributing to overcoming the dsRNases' degradation or endosomal escape in lepidopteran insects [70][71][72]75]. In our studies, we also observed that feeding 10µg of naked or nano-shielded dsRNA of various genes failed to cause mortality or generate different phenotypes in E. vittella, however, increasing dsRNA to 40µg for dsChitin synthase resulted in a reduction in pupation and adult emergence as well caused low frequencies of larval and pupal deformities.…”

“…Because the gut or hemolymph contains dsRNA-specific nucleases, numerous earlier investigations have also suggested these as one of the possible causes for dsRNA degradation in different insect species [9,15,16,26,[67][68][69]. Lepidopteran insects stomach nucleases may prevent sufficient amounts and high concentrations of dsRNA from reaching the cells, which results in ineffective RNAi; however, employing nanoparticles increased the RNAi effectiveness [70][71][72]. Current studies have effectively shown dsRNA degradation in the hemolymph of E. vittella and that nanoparticles may aid in nuclease escape and enhance RNAi in this organism.…”

A Combinatorial Nanobased Spray-Induced Gene Silencing Technique for Crop Protection and Improvement

“…Due to its core and outer shell components, they can fluently channel across the live cells of insects and pathogens, thus displaying extensive efficacy for the delivery of dsRNA. 25,26 Nanocarriers like star polycation (SP) can efficiently travel through the subsequent transdermal layers and, therefore, deliver dsRNA/siRNA by both oral and topical routes, in the case of insects. Oriental fruit flies, green pea aphids, and other pests get reduced when SPs are applied using a spray technique for disease prevention.…”

“…Fluorescent-based RNAi-NPs are delicately designed with a cationic polymer as its outer shell and a polyphenylene dendrimer as the inner shell consisting of fluorescent perylene-3,4,9,10-tetracarboxydiimide (PDI) as the chromophore that can obstruct H. armigera growth. Due to its core and outer shell components, they can fluently channel across the live cells of insects and pathogens, thus displaying extensive efficacy for the delivery of dsRNA. , …”

“…Due to its core and outer shell components, they can fluently channel across the live cells of insects and pathogens, thus displaying extensive efficacy for the delivery of dsRNA. 25 , 26 …”