Shah Parth N, Maistrou Sevasti, van Loon Joop J A, Dicke Marcel
Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands.
Laboratory of Entomology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands.
J Invertebr Pathol. 2025 Mar;209:108272. doi: 10.1016/j.jip.2025.108272. Epub 2025 Jan 31.
The larvae of the black soldier fly (BSFL), Hermetia illucens L. (Diptera: Stratiomyidae), are exposed to a diverse range of microorganisms within their feeding substrate that is mainly composed of decaying organic matter. In the current study, we evaluated the effect of an interaction with a Gram-negative bacterium, Pseudomonas protegens Pf-5, on the immune responses of the larvae of H. illucens. Five-day-old BSF larvae were injected with one of five doses of bacterial inoculum to assess survival. We observed dose-dependent mortality in BSF larvae to P. protegens infection, with mortality increasing with an increasing pathogen dose. Injection of more than 50 bacterial cells per larva resulted in 100 % larval mortality, while injection of one bacterial cell per larva caused only 20 % mortality. Phenoloxidase activity, an element of the immune response, correlated with the pathogen dose, increasing early for larvae injected with a high pathogen dose (i.e., 5000 bacterial cells per larva) and later for larvae injected with a low bacterial dose (i.e., one cell per larva). The expression of four genes encoding for antimicrobial peptides (AMPs), namely cecropin, defensin-A, defensin-like peptide 4, and attacin-A, displayed a treatment- and dose-specific expression pattern. Injection with either PBS (control) or different bacterial doses initially induced the upregulation of AMP genes; however, expression reduced over time in the control larvae. At high pathogen dose, all tested genes except hsp70 were consistently induced. The expression of all genes, except hsp70, was induced by low pathogen dose at 2 h, then reduced gradually and increased significantly at 15 h. These results collectively indicate that BSF larvae temporally modulate their immune responses, such as phenoloxidase activation and AMP gene expression, to combat a pathogen within their hemolymph.
黑水虻（Hermetia illucens L.，双翅目：水虻科）的幼虫在其主要由腐烂有机物组成的取食基质中会接触到各种各样的微生物。在本研究中，我们评估了与革兰氏阴性菌荧光假单胞菌Pf-5相互作用对黑水虻幼虫免疫反应的影响。给5日龄的黑水虻幼虫注射五种剂量细菌接种物中的一种以评估存活率。我们观察到黑水虻幼虫对荧光假单胞菌感染存在剂量依赖性死亡率，死亡率随病原体剂量增加而升高。每只幼虫注射超过50个细菌细胞会导致100%的幼虫死亡，而每只幼虫注射一个细菌细胞仅导致20%的死亡率。免疫反应的一个要素——酚氧化酶活性与病原体剂量相关，对于注射高病原体剂量（即每只幼虫5000个细菌细胞）的幼虫，其活性早期升高，而对于注射低细菌剂量（即每只幼虫一个细胞）的幼虫，其活性后期升高。四种编码抗菌肽（AMP）的基因，即天蚕素、防御素-A、防御素样肽4和攻击素-A，呈现出处理和剂量特异性的表达模式。注射磷酸盐缓冲盐水（PBS，对照）或不同细菌剂量最初会诱导AMP基因上调；然而，对照幼虫中的表达随时间降低。在高病原体剂量下，除hsp70外的所有测试基因均持续被诱导。除hsp70外，所有基因在低病原体剂量下于2小时被诱导，然后逐渐降低并在15小时显著升高。这些结果共同表明，黑水虻幼虫会暂时调节其免疫反应，如酚氧化酶激活和AMP基因表达，以对抗其血淋巴中的病原体。
