Functional characterization of developmentally critical genes in the white-backed planthopper: Efficacy of nanoparticle-based dsRNA sprays for pest control

Authors: GUO, HAUN - Guizhou University; LIU, XUAN-ZHENG - Guizhou University; LONG, GUI-JUN - Guizhou University; GONG, LANG-LANG - Guizhou University; ZHANG, MENG-QI - Guizhou University; MA, YUN-FENG - Guizhou University; Hull, Joe; DEWER, YOUSSEF - Agricultural Research Center Of Egypt; HE, MING - Guizhou University; HE, PENG - Guizhou University

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2022
Publication Date: 11/3/2022
Citation: Guo, H., Liu, X., Long, G., Gong, L., Zhang, M., Ma, Y., Hull, J.J., Dewer, Y., He, M., He, P. 2022. Functional characterization of developmentally critical genes in the white-backed planthopper: Efficacy of nanoparticle-based dsRNA sprays for pest control. Pest Management Science. 79(3):1048-1061. https://doi.org/10.1002/ps.7271.
DOI: https://doi.org/10.1002/ps.7271

Interpretive Summary: RNA interference (RNAi), a cellular mechanism for regulating gene expression, has been developed as a tool for assessing in vivo gene functionality and, more recently, has gained interest as an insect pest management tactic. While it has been successfully applied for some species of insects, limitations in how the RNAi triggering agents [e.g. double-stranded RNAs (dsRNAs) that are homologous to the target genes] are delivered continue to constrain wide-spread adoption of the technique. The utilization of nanoparticles as carriers/protectants, however, has potential to address stability issues common to naked dsRNAs and the development of sprayable formulations can bypass concerns regarding transgenic approaches. The utility of combing the two approaches was assessed in the white-backed planthopper, common pest of rice. Initially, the functional role of four genes associated with insect growth and development were evaluated via dsRNA microinjection. The resulting phenotypic effects (increased mortality and incidence of developmental defects) confirmed the criticality of all four genes. The efficacy of combining the dsRNAs with nanoparticles into a sprayable formulation was then assessed in trial cages with rice seedlings. Phenotypes comparable to those observed in the microinjection experiments support the utility of the sprayable nanoparticle delivery method. As such, the study lays the foundation for the further development and optimization of the technology for more practical applications.

Technical Abstract: BACKGROUND Epidermal growth factor receptor (EGFR), zinc finger homeodomain-2 (zfh-2), Abdominal-A (Abd-A), and Abdominal-B (Abd-B) regulate the growth and development of the insect abdomen. However, their potential roles in pest control have not been fully assessed. The development of insecticide resistance to multiple chemistries in the white-backed planthopper (WBPH), a major pest of rice, has prompted interest in novel pest control approaches that are ecologically friendly. Although pest management approaches based on double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) have potential, their susceptibility to degradation limits large-scale field applications. These limitations, however, can be overcome with nanoparticle–dsRNA complexes that have greater environmental stability and improved cellular uptake. RESULTS In this study, at 5 days post-injection, transcripts for the four gene targets were reduced relative to controls and all of the experimental groups exhibited significant phenotypic defects and increased mortality. To evaluate the potential of these gene targets for field applications, a nanocarrier– dsRNA spray delivery system was assessed for RNAi efficacy. At 11 days post- spray, significant phenotypic defects and increased mortality were observed in all experimental groups. CONCLUSION Taken together, the results confirm the suitability of the target genes (SfEGFR, Sfzfh-2, SfAbd-A, and SfAbd-B) for pest management and demonstrate the efficacy of the nanocarrier spray system for inducing RNAi-mediated knockdown. As such, the study lays the foundation for the further development and optimization of this technology for large-scale field applications.