The Route of Infection Influences the Contribution of Key Immunity Genes to Antibacterial Defense in Anopheles gambiae
The Route of Infection Influences the Contribution of Key Immunity Genes to Antibacterial Defense in Anopheles gambiae
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DOI：
10.1159/000511401
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发表时间：
2020-11-18
影响因子：
5.3
通讯作者：
Osta, Mike A.
中科院分区：
文献类型：
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作者：
Dekmak, Amira San;Yang, Xiaowei;Osta, Mike A.
昆虫对细菌感染的系统性免疫反应主要使用显微注射来研究，其中微生物直接注射到血腔中。虽然这种方法有助于定义血淋巴中的免疫信号传导途径和酶级联反应，但仍不清楚如果细菌在口腔感染后穿过中肠上皮后侵入血淋巴，全身免疫防御对宿主微生物抗性的贡献是否以及在多大程度上发生变化。在这里，我们解决这个问题，使用致病性粘质沙雷氏菌（Sm）DB 11菌株建立疟疾媒介冈比亚按蚊的全身感染，无论是通过败血症Sm注射或通过中肠交叉后喂养Sm。利用RNAi的功能遗传学研究，我们报告说，两个体液免疫因子，硫酯蛋白1和C型凝集素4，这在防御革兰氏阴性菌感染中起着关键作用，是必不可少的防御系统Sm感染建立通过注射，但他们成为寄生虫当Sm感染血淋巴后，口腔感染。对于蚊子Rel 2途径观察到类似的结果。令人惊讶的是，通过细胞松弛素D治疗阻断吞噬作用并不影响蚊子对通过任一途径建立的Sm感染的易感性。通过RNA-seq对蚊子中肠和肠的转录组学分析显示，这些组织中的转录反应在对以Sm为食的反应中更明显。差异表达的转录本的功能分类确定代谢基因作为最具代表性的类，在这两种途径的感染，而免疫基因在这两种途径的调节不良。我们还报告说，Sm口腔感染与属于不同的家庭，特别是剪辑结构域丝氨酸蛋白酶家族的几个免疫基因的显着下调。总之，我们的研究结果表明，感染途径不仅改变了关键免疫基因对宿主抗菌防御的贡献，而且还与中肠和肠中不同的转录反应有关，可能反映了宿主不同的适应策略。
Insect systemic immune responses to bacterial infections have been mainly studied using microinjections, whereby the microbe is directly injected into the hemocoel. While this methodology has been instrumental in defining immune signaling pathways and enzymatic cascades in the hemolymph, it remains unclear whether and to what extent the contribution of systemic immune defenses to host microbial resistance varies if bacteria invade the hemolymph after crossing the midgut epithelium subsequent to an oral infection. Here, we address this question using the pathogenic Serratia marcescens (Sm) DB11 strain to establish systemic infections of the malaria vector Anopheles gambiae, either by septic Sm injections or by midgut crossing after feeding on Sm. Using functional genetic studies by RNAi, we report that the two humoral immune factors, thioester-containing protein 1 and C-type lectin 4, which play key roles in defense against Gram-negative bacterial infections, are essential for defense against systemic Sm infections established through injection, but they become dispensable when Sm infects the hemolymph following oral infection. Similar results were observed for the mosquito Rel2 pathway. Surprisingly, blocking phagocytosis by cytochalasin D treatment did not affect mosquito susceptibility to Sm infections established through either route. Transcriptomic analysis of mosquito midguts and abdomens by RNA-seq revealed that the transcriptional response in these tissues is more pronounced in response to feeding on Sm. Functional classification of differentially expressed transcripts identified metabolic genes as the most represented class in response to both routes of infection, while immune genes were poorly regulated in both routes. We also report that Sm oral infections are associated with significant downregulation of several immune genes belonging to different families, specifically the clip-domain serine protease family. In sum, our findings reveal that the route of infection not only alters the contribution of key immunity genes to host antimicrobial defense but is also associated with different transcriptional responses in midguts and abdomens, possibly reflecting different adaptive strategies of the host.