Balancing nutrients in a toxic environment: the challenge of eating

• Published in: Insect science 2022-02, Vol.29 (1), p.289-303
• Main Authors: Wang, Peng, Vassão, Daniel G., Raguschke, Bettina, Furlong, Michael J., Zalucki, Myron P.
• Format: Article
• Language: English
• Subjects: Allyl isothiocyanate; Amino acids; Animals; Artificial diets; Carbohydrates; Detoxification; Diet; diet protein; Food; Food intake; Food sources; glucosinolate; gut metabolism; Helicoverpa armigera; Herbivores; Herbivory; High protein diet; Insects; Isothiocyanate; Larva; Metabolites; Moths; Nutrient content; Nutrient sources; Nutrients; Proteins; Secondary metabolites; Sinigrin; Toxins
• ISSN: 1672-9609; 1744-7917
• DOI: 10.1111/1744-7917.12923

Insect herbivores can regulate their food intake by mixing food sources with different nutrient content, but face the resulting challenge of ingesting various plant secondary metabolites. How insects deal with toxins in a complex nutrient environment is unclear. Here we investigated the influence of a classic plant secondary metabolite, allyl glucosinolate (sinigrin), and its hydrolyzed product allyl isothiocyanate (AITC), on the development of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) when fed on diets with different protein‐to‐carbohydrate (p : c) ratios. We also examined the effects of these toxins on larval biochemistry, by chemically analyzing the frass produced by insects feeding on the different diets. As expected, AITC had a greater negative effect than sinigrin on H. armigera life‐history traits. However, AITC at low concentration appeared to have a positive effect on some traits. Both sinigrin and AITC‐induced detoxification activity in the gut, and the reaction was related to diet protein concentration. High‐protein diets can provide the required free amino acid, especially cysteine, needed for the detoxification process. The nutrient content of the diet influences how plant secondary metabolites are handled, and the use of artificial diets in experiments investigating the metabolic fate of plant secondary compounds needs to be carefully evaluated. Graphical : In the current study, diets with different protein‐to‐carbohydrate (p​ : c) ratios (HC, high carbohydrate diet; OP, optimal diet; and HP, high protein diet) were mixed with allyl glucosinolate (sinigrin), or its hydrolyzed product allyl isothiocyanate (AITC), to investigate their effect to the development and detoxification ability of Helicoverpa armigera. Our results show life‐history traits of H. armigera were greatly affected by AITC‐treated diets. However, AITC at low concentration appeared to have a positive effect on some traits, indicating a hormesis phenomenon. Both sinigrin‐ and AITC‐induced detoxification activity in the gut, and the reaction was related to diet protein concentration. High‐protein diets that can provide enough required free amino acid, especially cysteine, implying a beneficial for the detoxification process.