Effects of SmartStax® and SmartStax® PRO maize on western corn rootworm (Diabrotica virgifera virgifera LeConte) larval feeding injury and adult life history parameters

Foliar spray double-stranded RNA targeting HvIAP1 induces high larval and adult mortality in Henosepilachna vigintioctopunctata

BACKGROUND

Exogenous double-stranded RNA (dsRNA) has the potential to serve as an effective alternative to conventional chemical pesticides for the control of insect pests, because it can specifically inhibit essential gene expression in these organisms. However, identifying suitable gene targets remains a crucial step in the development of RNA interference (RNAi)-based pest control strategies.

RESULTS

In this study, three apoptosis-related genes were selected to evaluate their potential for RNAi-induced lethality in Henosepilachna vigintioctopunctata via foliar spray dsRNAs. Our results revealed that silencing of HvIAP1 (inhibitor of apoptosis protein 1) had a significant lethal effect on larvae, whereas silencing of HvAIF1 and HvASPP1 did not, correlating with distinct expression patterns. Larvae ingested leaves sprayed with bacterially expressed dsHvIAP1 at a concentration of 100 ng/cm2 resulting in the impairment of cuticle tanning, cessation of feeding, and ultimately, 100% mortality within 7 days. In addition, the potential of dsHvIAP1 to mediate for adult control was also investigated and showed that administration of 200 ng/cm2 dsHvIAP1 resulted in 100% adult mortality within 9 days, accompanied by a significant reduction in leaf consumption and suppression of HvIAP1 expression compared with the dsGFP group.

CONCLUSIONS

Our findings demonstrate that HvIAP1 is a highly lethal molecular target with a notable difference in the concentration required for larval and adult mortality. These findings provide a foundation for the future development of RNAi pesticides for environmentally friendly control of H. vigintioctopunctata. © 2025 Society of Chemical Industry.

Optimizing dsRNA sequences for RNAi in pest control and research with the dsRIP web platform

BACKGROUND

RNA interference (RNAi) is a tool for studying gene function and has emerged as a promising eco-friendly alternative to chemical pesticides. RNAi relies on delivering double-stranded RNA (dsRNA), which is processed into small interfering RNA (siRNA) to silence genes. However, so far, knowledge and tools for optimizing the dsRNA sequences for maximum efficacy are based on human data, which might not be optimal for insect pest control.

RESULTS

Here, we systematically tested different siRNA sequences in the red flour beetle Tribolium castaneum to identify sequence features that correlated with high efficacy using pest control as a study case. Thermodynamic asymmetry, the absence of secondary structures, and adenine at the 10th position in antisense siRNA were most predictive of insecticidal efficacy. Interestingly, we also found that, in contrast to results from human data, high, rather than low, GC content from the 9th to 14th nucleotides of antisense was associated with high efficacy. Consideration of these features for the design of insecticidal dsRNAs targeting essential genes in three insect species improved the efficacy of the treatment. The improvement was associated with a higher ratio of the antisense, rather than sense, siRNA strand bound to the RNA-induced silencing complex. Finally, we developed a web platform named dsRIP, which offers tools for optimizing dsRNA sequences, identifying effective target genes in pests, and minimizing risk to non-target species.

CONCLUSIONS

The identified sequence features and the dsRIP web platform allow optimizing dsRNA sequences for application of RNAi for pest control and research.

Can the molecular and transgenic breeding of crops be an alternative and sustainable technology to meet food demand?

The gradual increase in the worldwide population represents various challenges, and one of the most alarming being the food demand. Historically technological advances led to the development of crops that meets the requirements and demands. Currently, molecular breeding unlocks the genetic potential of crops for their improvement, positioning it as a key technology for the development of new crops. The implementation of OMICs sciences, such spatial and single cell transcriptomics is providing a large and precise information, which can be exploited for crop improvement related to increasing yield, improving the nutritional value; designing new strategies for diseases resistance and management and for conserving biodiversity. Furthermore, the use of new technologies such CRISPR/CAS9 brought us the ability to modify the selected regions of the genome to select the superior's genotypes at a short time and the use of artificial intelligence aid in the analysis of big data generated by OMICS sciences. On the other hand, the application of molecular improvement technologies open up discussion on global regulatory measures, the socio-economic and socio-ethics, as the frameworks on its global regulation and its impact on the society create the public perception on its acceptance. In this review, the use and impact of OMICs sciences and genetic engineering in crops development, the regulatory measures, the socio-economic impact and as well as the mediatic information on genetically modified crops worldwide is discussed along with comprehensive insights on the potential of molecular plant breeding as an alternative and sustainable technology to meet global food demand.

Effective target genes for RNA interference-based management of the cabbage stem flea beetle

The cabbage stem flea beetle (CSFB, Psylliodes chrysocephala) is a key pest of oilseed rape. The ban on neonicotinoids in the European Union due to environmental concerns and the emergence of pyrethroid-resistant populations have made the control of CSFB extremely challenging. In search of a solution, we have recently shown that RNA interference (RNAi) has potential in the management of CSFB. However, the previously tested target genes for RNAi-mediated pest control (subsequently called target genes) exhibited moderate and slow-acting lethal effects. In this study, 27 double-stranded RNAs (dsRNAs) were orally delivered to identify highly effective target genes in CSFB adults by leveraging the findings of a genome-wide RNAi screen in Tribolium castaneum. Our screen using 500 ng of dsRNA identified 10 moderately effective (> 50% mortality) and 4 highly effective target genes (100% mortality in 8-13 days). The latter mainly included proteasome subunits. Gene expression measurements confirmed target gene silencing and dose-response studies revealed LD50 values as low as ~20 ng in 14 days following a single exposure to dsRNA. Four highly effective dsRNAs also inhibited leaf damage (up to ~75%) and one affected locomotion. The sequences of promising target genes were subjected to in silico target prediction in non-target organisms, for example, beneficials such as honeybees, to design environmentally friendly dsRNAs. Overall, the study provides valuable insights for the development of dsRNA-based insecticides against CSFB.

Resistance management and integrated pest management insights from deployment of a Cry3Bb1+ Gpp34Ab1/Tpp35Ab1 pyramid in a resistant western corn rootworm landscape

In Nebraska USA, many populations of western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, now exhibit some level of resistance to all corn rootworm-active Bacillus thuringiensis Berliner (Bt) proteins expressed in commercial hybrids. Therefore, a study was conducted in northeast Nebraska from 2020-2022 to reevaluate current corn rootworm management options in continuous maize (consecutive planting for ≥2 years). Results from on-farm experiments to evaluate a standard soil-applied insecticide (Aztec® 4.67G) in combination with non-rootworm Bt or rootworm-active Bt pyramided maize (Cry3Bb1 + Gpp34Ab1/Tpp35Ab1) are reported within the context of WCR Bt resistance levels present. Corrected survival from Bt pyramid single-plant bioassays (<0.3, 0.3-0.49, >0.5) was used to place populations into 3 resistance categories. Variables evaluated included root injury, adult emergence, proportion lodged maize, and grain yield. Key results: A composite analysis of all populations across resistance levels indicated that addition of soil insecticide to Bt pyramid significantly reduced adult emergence and lodging but did not significantly increase root protection or yield. Within and among resistance category analyses of root injury revealed that the Bt pyramid remained highly efficacious at any non-rootworm Bt root injury level when resistance was absent or low. When corrected survival was >0.3, mean Bt pyramid root injury tracked more closely in a positive linear fashion with mean non-rootworm Bt root injury (rootworm density x level of resistance interaction). Similar trends were obtained for adult emergence but not yield. Mean Bt pyramid root injury rating was <0.75 in most populations with Bt resistance, which contributed to no significant yield differences among categories. Results are discussed within the context of IPM:IRM tradeoffs and the need to reduce WCR densities in this system to decrease the impact of the density x resistance interaction to bridge use of current pyramids with new technologies introduced over the next decade.