Effects of aflatoxin B on metabolism- and immunity-related gene expression in Hermetia illucens L. (Diptera: Stratiomyidae).

Contamination of food products with mycotoxins such as aflatoxin B (AFB) poses a severe risk to human health. Larvae of the black soldier fly (BSFL), Hermetia illucens (Diptera: Stratiomyidae), can successfully metabolize AFB without any negative consequences on their survival or growth. Organic waste streams contaminated with mycotoxins can be upcycled into protein-rich BSFL as an alternative feed for livestock and the left-over feed residue into nutrient-rich crop fertilizers. However, the underlying mechanisms that allow BSFL to metabolize AFB are unknown. In this study, five-day-old BSFL were fed with either a control or an AFB-spiked (20 μg/kg) diet to elucidate the underlying mechanisms. Larval samples were collected at three timepoints (6 h, 24 h and 72 h) and subjected to RNA-Seq analysis to determine gene expression patterns. Provision of an AFB-spiked diet resulted in an up-regulation of 357 and a down-regulation of 929 unique genes. Upregulated genes include multiple genes involved in AFB metabolism in other (insect) species. Downregulated genes were generally involved in the insects' growth, development, and immunity. BSFL possesses a diverse genetic arsenal that encodes for enzymes capable of metabolizing AFB without trade-offs on larval survival. In conclusion, the adverse impact of AFB exposure on immunity-related processes is observed in the transcriptomic response, and is indicative of a trade-off between detoxification and immune responses.