Effects of targeting eye color in Tenebrio molitor through RNA interference of tryptophan 2,3-dioxygenase (vermilion): Implications for insect farming

Authors: Oppert, Brenda; CHU, FU-CHYUN - North Carolina State University; REYNA, STEVEN - North Carolina State University; PINZI, SOFIA - North Carolina State University; Adrianos, Sherry; Perkin, Lindsey; LORENZEN, MARCE - North Carolina State University

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 3/1/2019
Citation: Oppert, B.S., Chu, F., Reyna, S., Pinzi, S., Adrianos, S.L., Perkin, L.C., Lorenzen, M. 2019. Effects of targeting eye color in Tenebrio molitor through RNA interference of tryptophan 2,3-dioxygenase (vermilion): Implications for insect farming. Archives of Insect Biochemistry and Physiology. 10(1):e21546. https://doi.org/10.1002/arch.21546.
DOI: https://doi.org/10.1002/arch.21546

Interpretive Summary: Transforming insect eye color is a useful tool in genetic research because it provides an easy to see marker that can be linked to other transformations that are more difficult to detect. The yellow mealworm, Tenebrio molitor, is a stored product insect pest that is also farmed for animal feed and has potential as an alternative source of protein for humans. To successfully develop insects as a viable food crop, genetic tools are needed to optimize characteristics such as protein content. We demonstrated that we can make white-eyed mealworms, both larvae and adults, by modifying the expression of an eye color gene - previously identified in other insects -that contributes to their normal black eye color. We found that the modified expression of this gene also caused changes in the expression of other genes, providing insights into how this gene is not only involved in eye color, but also in other metabolic pathways. These data lay the groundwork for generating transgenic marker strains of T. molitor for application in genetic manipulations to develop mealworms as an alternative food source.

Technical Abstract: The gene vermilion encodes tryptophan 2,3-dioxygenase, part of the ommochrome pathway, and is responsible for the dark pigmented eyes in some insects, including beetles. Using RNA interference, we targeted the vermilion gene ortholog in embryos and pupae of the yellow mealworm, Tenebrio molitor, resulting in larvae and adults, respectively, that lack eye pigment. RNA-Seq was used to analyze the impact of RNA interference on gene expression. We found a 425-fold reduction in vermilion gene expression (p=0.0003), as well as significant (p<0.05) differential expression of 109 other putative genes, mostly downregulated. Enrichment analysis of gene ontology terms found in the differentially-expressed dataset included enzymes known to be involved in the ommochrome pathway. However, enrichment also included genes involved in protein translocation to the endoplasmic reticulum, signal transduction, G-protein coupled receptor signaling, cell cycle arrest, mannose biosynthesis, and vitamin transport. These data demonstrate that knockdown of vermilion in T. molitor results in loss of eye color and suggest other interrelated genes in the vermilion metabolic pathway. Importantly, these data provide technology to generate transgenic marker strains of T. molitor for application in genetic manipulation of mealworms as alternative food sources.