Gut microbiota modulates various physiologic processes in insects, such as nutrition, metabolic homeostasis, and pathogen exclusion. Maintaining a normal microbiome is an essential element of the gut homeostasis, requiring an extensive network of regulatory immune responses. The molecular mechanisms driving these various effects and the events leading to the establishment of a normal microbiota in insects are still largely unknown. In this study, the NF-kB (IMD and Toll) signaling pathways in the gut of Galleria mellonella and their roles in the regulation of its gut microbes were assessed. For this, the transcript levels of the IMD pathway (Imd and Relish) and the Toll pathway (Spätzle and Dif/Dorsal) genes were analyzed and the results showed that all the genes were expressed in the gut of G. mellonella. Silencing of Relish resulted in reduced expression levels of the IMD pathway genes and antimicrobial peptides (AMPs) followed by overpopulation of gut bacteria. Antibiotics-treated larvae showed lower expression levels of the IMD and Toll pathway genes followed by lower AMPs expression levels. The expression level of caudal decreased in the antibiotics-treated larvae compared with the controls. Together, these data suggest that the IMD and Toll pathways are active in the gut of G. mellonella. The IMD pathway gene, relish functions in the regulation of gut microbes in this insect model.

中文翻译：

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先天免疫基因 Relish 和 Caudal 通过调节大蜡螟中的抗菌肽共同促进肠道免疫稳态。

肠道微生物群调节昆虫的各种生理过程，如营养、代谢稳态和病原体排除。维持正常的微生物组是肠道稳态的基本要素，需要广泛的调节免疫反应网络。驱动这些各种影响的分子机制以及导致昆虫正常微生物群建立的事件在很大程度上仍是未知的。在这项研究中，评估了大蜡螟肠道中的 NF-kB（IMD 和 Toll）信号通路及其在调节肠道微生物中的作用。为此，分析了 IMD 通路（Imd 和 Relish）和 Toll 通路（Spätzle 和 Dif/Dorsal）基因的转录水平，结果表明所有基因都在大蜡螟的肠道中表达。Relish 的沉默导致 IMD 通路基因和抗菌肽 (AMP) 的表达水平降低，随后肠道细菌数量过多。抗生素处理的幼虫表现出较低的 IMD 和 Toll 通路基因表达水平，随后是较低的 AMPs 表达水平。与对照组相比，抗生素处理的幼虫尾部的表达水平降低。总之，这些数据表明 IMD 和 Toll 通路在 G. mellonella 的肠道中是活跃的。IMD 通路基因在该昆虫模型中具有调节肠道微生物的功能。与对照组相比，抗生素处理的幼虫尾部的表达水平降低。总之，这些数据表明 IMD 和 Toll 通路在 G. mellonella 的肠道中是活跃的。IMD 通路基因在该昆虫模型中具有调节肠道微生物的功能。与对照组相比，抗生素处理的幼虫尾部的表达水平降低。总之，这些数据表明 IMD 和 Toll 通路在 G. mellonella 的肠道中是活跃的。IMD 通路基因在该昆虫模型中具有调节肠道微生物的功能。