Silkworm (Bombyx mori) is an important economic insect. Bombyx mori, which is exposed to sublethal doses of pesticides, has a low or no mortality rate, while it is susceptible to infections triggered by foreign pathogens. The immune regulatory mechanism of silkworms caused by trace pesticides still remains unclear. The midgut is the major organ of silkworm for digestion and nutrient absorption, and it plays a critical defensive role against pathogens. In the present study, the silkworm was susceptible to Enterobacter cloacae sp. (E. cloacae) after exposure to sublethal dose of phoxim. The body weight and survival rate of the phoxim-E. cloacae co-treatment group were significantly decreased after 120 h of treatment compared with the phoxim treatment group. The immune responses and expressions of immune-related genes were dysregulated in the midgut of silkworm following exposure to phoxim. Digital gene expression (DGE) analysis revealed that 44 immune response-related and immune defense-related genes were differentially expressed. qRT-PCR results indicated that the transcriptional levels of antimicrobial peptide genes Bmdefensin1, BmcecA, Bmglv1, Bmglv2, Bmmoricin and BmmoricinB3 were down-regulated by 0.77-, 0.37-, 0.05-, 0.19-, 0.34- and 0.54-fold, respectively. The transcriptional levels of Toll signaling pathway genes Bmcactus, Bmspatzle and Bmrel were down-regulated by 0.4-, 0.37- and 0.96-fold, respectively. Peritrophic membrane (PM) protein-related genes BmCBP-02, BmPM-41, BmPM-43 and BmCDA7 were down-regulated by 0.18-, 0.02-, 0.66- and 0.16-fold, respectively. The expressions of Toll signaling pathway genes were down-regulated at 48 h and 72 h. Immune deficiency (IMD) and Janus kinase and signal transducer and activator of transcription (JAK/STAT) signaling pathway genes were dysregulated after phoxim exposure. These results indicated that phoxim might cause damage to the PM and reduce the immune response of the silkworm, leading to susceptibility of silkworm to disease and damage from foreign pathogens.

中文翻译：

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辛硫磷农药对家蚕中肠免疫系统的影响

家蚕（Bombyx mori）是一种重要的经济昆虫。家蚕暴露于亚致死剂量的杀虫剂中，死亡率很低或没有，但容易受到外来病原体引发的感染。微量农药对家蚕的免疫调节机制尚不清楚。中肠是家蚕消化和吸收营养的主要器官，对病原体起着至关重要的防御作用。在本研究中，家蚕对阴沟肠杆菌属易感。(E. cloacae) 暴露于亚致死剂量的辛硫磷后。辛硫磷的体重和存活率。与辛硫磷治疗组相比，治疗120小时后泄殖腔联合治疗组显着降低。暴露于辛硫磷后，家蚕中肠的免疫反应和免疫相关基因的表达失调。数字基因表达（DGE）分析显示44个免疫反应相关和免疫防御相关基因差异表达。qRT-PCR结果表明抗菌肽基因Bmdefensin1、BmcecA、Bmglv1、Bmglv2、Bmmoricin和BmmoricinB3的转录水平分别下调0.77-、0.37-、0.05-、0.19-、0.34-和0.54-倍。Toll 信号通路基因 Bmcactus、Bmspatzle 和 Bmrel 的转录水平分别下调 0.4、0.37 和 0.96 倍。围营养膜 (PM) 蛋白相关基因 BmCBP-02、BmPM-41、BmPM-43 和 BmCDA7 分别下调 0.18、0.02、0.66 和 0.16 倍。Toll 信号通路基因的表达在 48 h 和 72 h 下调。辛硫磷暴露后，免疫缺陷 (IMD) 和 Janus 激酶以及信号转导和转录激活因子 (JAK/STAT) 信号通路基因失调。这些结果表明辛硫磷可能对 PM 造成损害，降低家蚕的免疫反应，导致家蚕易感疾病和外来病原体的损害。