RNA sequencing analysis reveals the role of choline acetyltransferase in regulating development, reproduction, and insecticide susceptibility in Tribolium castaneum (Coleoptera: Tenebrionidae)

Abstract

Choline acetyltransferase (Tcchat) is essential for metamorphosis, reproduction, and susceptibility to insecticide in Tribolium castaneum. However, the mechanisms through which Tcchat contributes to these biological processes remain poorly understood. Here we report the findings of RNA sequencing-based transcriptome profiling of T. castaneum following RNA interference against Tcchat. In all, 173 differentially expressed genes were identified: 120 upregulated genes and 53 downregulated genes. Gene Ontology analysis classified the genes into 30 functional groups. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the genes were distributed over 22 different pathways. Silencing Tcchat reduced the activity of endopeptidase and inhibited regulation of protein decomposition in the beetles. Hence, knockdown of Tcchat inhibited the synthesis of chitinase and serine protease, which disturbed embryonic development in T. castaneum, thus affecting its development and reproduction. RNA interference of Tcchat also suppressed the synthesis of cytochrome P450 in the extracellular region and adversely affected normal functioning of the lysosomal pathway, which might have hindered the insects' ability to recognize, phagocytose, and degrade exogenous toxic substances, resulting in increased mortality. Furthermore, knockdown of Tcchat increased the susceptibility of larvae to carbamate and organophosphate insecticides, which supports the notion that Tcchat is indeed involved in susceptibility to insecticide in T. castaneum. Finally, Tcchat knockdown adults showed progressively reduced locomotor activity. These results provide novel insights into biological processes affected by Tcchat and provide a potential theoretical basis for the biological control of T. castaneum.