Transcriptomic response of Hermetia illucens L. (Diptera: Stratiomyidae) to wounding and Gram-negative bacterial infection

The larvae of black soldier fly (BSF), Hermetia illucens L., are of economic importance due to their potential as livestock feed. However, the knowledge on their immune response to infection and wounding remains limited. In this study, we uncover the transcriptomic response of BSF larvae to wounding as well as infection with Gram-negative pathogen, Pseudomonas protegens Pf-5 at multiple timepoints. We observed that initially the BSF larvae generated a common immune response to both wounding and infection. However, the immune response is only upregulated in infected larvae over time, while the gene expression in response to wounding reduced over time. Genes encoding for signalling molecules such as PGRP-SA, Relish as well as genes encoding antimicrobial peptides like cecropin, defensin and attacin contributed primarily to BSF larvae's immune responses to both wounding as well as infection. Overall design: Five-day old BSF larvae were injected with a) PBS (positive-controls), or b) 5000 cells of Pseudomonas protegens Pf-5, and c) untreated BSF larvae were set-up as negative controls. Samples were collected from each treatment at 2 h, 6 h and 13 h post-treatment respectively. Total RNA was extracted and sequenced. Wounding response was quantified by comparing PBS-injected larvae to untreated larvae, and response to infection was quantified by comparing bacteria-injected larvae to PBS-injected larvae at respective timepoints.