Effect of the rearing diet on gene expression of antimicrobial peptides in Hermetia illucens (Diptera: Stratiomyidae)

Abstract

Insect proteins have been proposed for human and animal food production. Safeguarding the health status of insects in mass rearing allows to obtain high-quality products and to avoid severe economic losses due to entomopathogens. Therefore, new strategies for preserving insect health must be implemented. Modulation of the insect immune system through the diet is one such strategy. We evaluated gene expression of two antimicrobial peptides (one defensin and one cecropin) in Hermetia illucens (L.) (Diptera: Stratiomyidae) reared on different diets. Analyses were performed on prepupae and 10-day-old larvae reared on cereal-and municipal organic waste-based diets and on only prepupae reared on a cereal-based diet supplemented with sunflower, corn, or soybean oil. The inclusion of sunflower oil at different points in the cereal-based diet was also evaluated. Moreover, diet-driven differences in the inhibitory activity of the hemolymph were tested against Escherichia coli DH5α and Micrococcus yunnanensis HI55 using diffusion assays in solid media. Results showed that a municipal organic waste-based diet produced a significant overexpression of antimicrobial peptides only in prepupae. Inclusion of vegetable oils caused an upregulation of at least one peptide, except for the corn oil. Higher expression of both genes was observed when sunflower oil was added 5 days before pupation. All hemolymph samples showed an inhibitory activity against bacteria colonies. Our results suggest that municipal organic waste-based diet and vegetable oil-added diet may successfully impact the immune system of H. illucens. Such alternatives may also exist for other species of economic interest.

Immune Responses of the Black Soldier Fly Hermetia illucens (L.) (Diptera: Stratiomyidae) Reared on Catering Waste

“…Nutrient-poor diets and non-optimal protein–carbohydrate ratios result in a lower production of AMPs and hemocytes and a decrease in the insect endogenous bacteria [ 25 , 50 , 51 ]. The effect of the diet on insect immune responses has been highlighted [ 27 , 28 , 29 , 30 , 31 ], but the diet-mediated effect on both growing performance and immunity is still poorly investigated both in useful and pest insects. For example, the preference of the cabbage moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) for the mustard plant is well known, despite its relatively poor performance on this plant.…”

“…Reactions were performed with the SensiMixTM SYBR ® No-Rox kit [Bioline Meridian Bioscience, London, UK] using primers targeting the defensin (Forward: 5′-TCGTCCCATGGCAATACAAT-3′ and Reverse 5′-TAGTGGAGCAGCATTATCGGG-3′) and cecropin coding genes (Forward: 5′-GGTCAAAGCGAAGCTGGTT-3′ and Reverse 5′-TGCCAGAACATTGGCTCCTT-3) designed by Candian et al [ 31 ] on AMP protein sequences predicted by the transcriptome analysis by Vogel et al [ 25 ]. Actin coding gene (Forward: 5′-TTCGAGCAGGAAATGGCCAC-3′ and Reverse 5′-TTGGAAGAGAGCCTCTGGAC-3′) was used as reference gene [ 34 ].…”

“…In order to extract the hemolymph, the protocol designed by Tabunoki et al [ 36 ] and slightly modified as described in Candian et al [ 31 ] was used. Briefly, the insect’s thorax was gently injured with a scalpel, then all steps were performed maintaining the samples directly on ice.…”

“…The possibility of modulating both the cellular and humoral immune responses of an insect through the diet has only recently been highlighted [ 27 , 28 , 29 , 30 , 31 ]. The effect of the diet on the expression of AMPs, a key component of the insect’s humoral responses, in BSF has been recorded providing diets containing high microbial loads or supplemented with cellulose, chitin, lignin, brewer’s grains, protein, and sunflower oil [ 25 , 31 ]. Variation in the diet of Hyphantria cunea Drury [Lepidoptera: Erebidae] results in an increase in the hemocytes’ number in the hemolymph [ 32 ].…”

An alternative peptone preparation using Hermetia illucens (Black soldier fly) hydrolysis: process optimization and performance evaluation

“…HIL acts as a bulwark against harmful microbes like Escherichia coli and Salmonella . During the 10–20-day breeding phase, the larvae synthesize a high concentration of antibacterial peptides, creating an inhospitable environment for bacterial and fungal growth ( Secci et al, 2018 ; Cullere et al, 2019 ; Candian, Meneguz & Tedeschi, 2023 ; Candian et al, 2023 ). HIL also protects against typical mycotoxins such as deoxynivalenol, fumonisin 1 and 2, and zearalenone in HIL biomass, regardless of the nature of the substrate on which they are reared ( Bosch et al, 2017 ; Camenzuli et al, 2018 ; Leni et al, 2019 ).…”