Functional characterization of tyrosine melanin genes in the white-backed planthopper and utilization of a spray-based nanoparticle-wrapped dsRNA technique for pest control

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

Submitted to: International Journal of Biological Macromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2022
Publication Date: 1/7/2023
Citation: Guo, H., Long, G., Liu, X., Ma, Y., Zhang, M., Gong, L., Dewer, Y., Hull, J.J., Wang, M., Wang, Q., He, M., He, P. 2023. Functional characterization of tyrosine melanin genes in the white-backed planthopper and utilization of a spray-based nanoparticle-wrapped dsRNA technique for pest control. International Journal of Biological Macromolecules. 230. Article 123123. https://doi.org/10.1016/j.ijbiomac.2022.123123.
DOI: https://doi.org/10.1016/j.ijbiomac.2022.123123

Interpretive Summary: For insects, body coloration typically involves genes linked with melanization and sclerotization (hardening of the cuticle), two processes essential for insect development. Consequently, genes related to these functions have been proposed as candidates for development as pest management targets. To examine the utility of targeting these processes in the white-backed planthopper, a common pest of rice, the functional roles of seven genes (aaNAT, black, DDC, ebony, tan, tyrosine hydroxylase, and yellow) were characterized. Injection-based RNA interference (RNAi), a cellular mechanism that regulates target mRNA transcript levels in response to injected nucleic acids, was used to determine how each of the genes impact planthoppers in terms of growth and development, cuticular coloration, and mortality. Compared with control injections, all of the targets had clear effects on planthopper coloration; however, tyrosine hydroxylase RNAi had the most pronounced effects on planthopper mortality. To assess the efficacy of a spray-based RNAi method for potential field applications, a sprayable formulation of tyrosine hydroxylase dsRNAs complexed with nanoparticle carriers was developed and tested. Phenotypes comparable to those observed in the injection experiments (high mortality and atypical cuticular coloration) support the utility of the topical approach and highlight the potential of tyrosine hydroxylase as a pest management target.

Technical Abstract: As a significant rice pest of rice the white-backed planthopper (WBPH) Sogatella furcifera is a focus of pest management. However, traditional chemical-based control methods risk the development of pesticide resistance as well as severe ecological repercussions. Consequently, new strategies for control are needed. Although nanoparticle-encapsulated dsRNAs provide a promising alternative method for sustainable pest management, targets specific to WBPH have yet to be optimized. Epidermal melanization and sclerotization are essential for insect development and metabolism. As such, genes related to these functions are candidate pest management targets. One such group of genes of interest as potential targets are the tyrosine-melanin pathway genes that regulate cuticular coloration. A subset of this gene group was identified in the WBPH genome based on homology with the brown planthopper proteins aaNAT, black, DDC, ebony, tan, TH, and yellow. The seven genes identified were functionally characterized in terms of body color phenotypes, developmental effects, and mortality. Microinjection-based RNAi of SfDDC, Sfblack, SfaaNAT, and Sftan caused bodies to turn black, whereas Sfyellow-y and Sfebony knockdown resulted in yellow bodies. SfTH knockdown WBPH were characterized by pale-colored bodies and high mortality. Additionally, an Escherichia coli expression system for large-scale dsRNA production was coupled with star polycation nanoparticles to develop a sprayable RNAi method targeting SfTH that induced high WBPH mortality rates on rice seedlings. These findings lay the groundwork for the development of large-scale dsRNA nanoparticle sprays as a WBPH control method.