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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #358057

Research Project: Ecologically Based Pest Management in Western Crops Such as Cotton

Location: Pest Management and Biocontrol Research

Title: RNAi-mediated knockdown of eye coloration genes in the western tarnished plant bug (Lygus hesperus)

Author
item Brent, Colin
item Hull, Joe

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2018
Publication Date: 12/26/2018
Citation: Brent, C.S., Hull, J.J. 2018. RNAi-mediated knockdown of eye coloration genes in the western tarnished plant bug (Lygus hesperus). Archives of Insect Biochemistry and Physiology. 100(2):e21257. https://doi.org/10.1002/arch.21527.
DOI: https://doi.org/10.1002/arch.21527

Interpretive Summary: Insect eye coloration arises from the accumulation of various pigments. A number of genes that function in the biosynthesis (vermilion, cinnabar, cardinal) and importation (karmoisin, white, scarlet, and brown) of these pigments and their precursors have been identified in diverse species and used as markers for transgenesis and gene editing. To examine their suitability as visible markers in Lygus hesperus (western tarnished plant bug), we identified seven gene sequences similar to those proteins determining eye color in the fruitfly, Drosophila melanogaster. Consistent with their proposed role, each of the genes was expressed in adult heads during development. RNA interference was used to suppress the expression of these proteins, resulting in eyes that differed from the uniform dark brown of normally developing Lygus bugs. Silencing expression of karmoisin, vermilion, cinnabar, cardinal, and scarlet produced eyes characterized by a red band along the interior edge between the mouth and antenna. Disrupting white or brown produced eyes with a uniform light brown color. White knockdown also produced cuticular and behavioral defects. Collectively, the results suggest that cardinal would produce the most suitable marker for developing gene editing methods in Lygus.

Technical Abstract: Insect eye coloration arises from the accumulation of various pigments. A number of genes that function in the biosynthesis (vermilion, cinnabar, cardinal) and importation (karmoisin, white, scarlet, and brown) of these pigments and their precursors have been identified in diverse species and used as markers for transgenesis and gene editing. To examine their suitability as visible markers in Lygus hesperus (western tarnished plant bug), transcriptomic data were screened for sequences exhibiting homology with the Drosophila melanogaster proteins. Complete open reading frames encoding putative homologs for all seven genes were identified. Bioinformatic-based sequence and phylogenetic analyses supported initial annotations as eye coloration genes. Consistent with their proposed role, each of the genes was expressed in adult heads as well as throughout nymphal and adult development. RNA interference-mediated knockdown via injected double-stranded RNAs corresponding to ~ 500-bp fragments of the genes of interest resulted in phenotypes that differed from the uniform dark brown of both wild-type and control injected insects. Adult eyes of those injected with dsRNAs for karmoisin, vermilion, cinnabar, cardinal, and scarlet were characterized by a red band along the medial margin extending from the rostral terminus to the antenna. In contrast, eyes of insects injected with dsRNAs for both white and brown were a uniform light brown. White knockdown also produced cuticular and behavioral defects. Based on its expression profile and robust visible phenotype, cardinal would likely prove to be the most suitable marker for developing gene editing methods in Lygus.