Antimicrobial peptide expression in the cockroach gut during enterobacterial infection is specific and influenced by type III secretion.
Antimicrobial peptide expression in the cockroach gut during enterobacterial infection is specific and influenced by type III secretion.
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肠道细菌感染期间蟑螂肠道中抗菌肽的表达是特异性的，并受III型分泌的影响。
作者：
杂食性共生蟑螂，如德国小蠊（Blattella germanica）是肠道细菌病原体的宿主和媒介。一种有利于频繁接触各种细菌的生活方式可能导致这些昆虫进化出独特的先天免疫系统。昆虫的先天免疫反应在很大程度上依赖于一般的机制来感知和消除外来微生物。然而，先前对普通同体蟑螂基因组的分析显示，相对于大多数全变性昆虫模型和载体，病原体相关分子模式（PAMP）受体和抗菌肽（amp）的数量显著增加，这支持了一种有趣的可能性，即蟑螂可能在其免疫系统中编码增强的识别能力，并可能具有增强的微调先天免疫反应的能力。研究蟑螂对肠杆菌感染的反应，为我们在生物学和医学相关的背景下扩展昆虫先天免疫调节的基础知识提供了机会。德国蟑螂可以在肠道中同时携带沙门氏菌、鼠伤寒沙门氏菌和大肠杆菌，而不经历发病机制。前者在肠道中定植并复制，而后者仅短暂存在。我们假设先天免疫反应的差异可能是两种肠杆菌感染动力学差异的原因或结果。为了验证这一假设，我们采用qRT-PCR方法分析了德国蟑螂在摄入活肠杆菌或热杀肠杆菌1和24 h后肠道中编码代表性amp （Attacins, Blattellicin, Defensins）的5个基因的表达。研究人员发现，摄入野生型活鼠伤寒沙门氏菌可诱导AMP表达，而摄入活大肠杆菌、热灭鼠伤寒沙门氏菌或缺乏III型分泌系统的活鼠伤寒沙门氏菌突变株则不能诱导AMP表达。这些结果表明，蟑螂免疫系统对摄入高水平细菌PAMPs（如肽聚糖）的刺激没有反应。相反，AMP在肠道中的表达似乎是由涉及III型分泌的活跃细菌定植诱导的。我们推测，这种形式的调节可能已经进化到防止过度激活免疫系统从频繁摄入无害的，非定植的，或无活力的细菌。虽然还需要进一步的工作来描述我们观察到的分子机制，但我们的发现为蟑螂对化脓性环境的免疫适应以及这些昆虫调节细菌病原体传播的因素提供了重要的新见解。摘要：本研究表明，抗菌肽基因在德国蜚蠊肠道中的表达可能具有高度特异性，响应于III型分泌物依赖的定植过程，而不是一般的细菌相关分子模式。这一发现为蟑螂对化粪池环境的免疫适应以及这些昆虫调节细菌病原体传播的因素提供了新的见解。
Omnivorous synanthropic cockroaches, such as the German cockroach (Blattella germanica), are reservoirs and vectors of enteric bacterial pathogens. A lifestyle conducive to frequent encounters with high loads of diverse bacteria may have led to the evolution of unique innate immune systems in these insects. The innate immune response of insects relies largely on generalized mechanisms to sense and eliminate foreign microbes. However, analyses of the genomes of common synanthropic cockroaches previously revealed a repertoire of pathogen associated molecular pattern (PAMP) receptors and antimicrobial peptides (AMPs) that is significantly expanded relative to most holometabolous insect models and vectors, supporting the intriguing possibility that cockroaches may encode enhanced recognition within their immune system and may possess an enhanced capacity to fine tune innate immune responses. Investigating how cockroaches respond to infection with enterobacteria provides the opportunity to expand our fundamental knowledge of the regulation of insect innate immunity in a context that is biologically and medically relevant. German cockroaches can harbor both Salmonella enterica serovar Typhimurium and Escherichia coli in their gut without experiencing pathogenesis. The former colonizes the gut and replicates while the latter persists only transiently. We hypothesized that differences in the innate immune response may contribute to or result from the difference in infection dynamics between the two enterobacteria. To test this hypothesis, we used qRT-PCR to analyze expression of five genes encoding representative AMPs (Attacins, Blattellicin, Defensins) in the gut of German cockroaches 1 and 24 h after ingestion of live or heat-killed enterobacteria. We found that robust AMP expression was induced in response to ingestion of a live wild-type strain of S. Typhimurium, but not in response to live E. coli, heat-killed S. Typhimurium, or a live mutant strain of S. Typhimurium lacking type III secretion systems. These results indicate that the cockroach immune system does not respond to stimulation with high levels of ingested bacterial PAMPs such as peptidoglycan. Rather, AMP expression in the gut appears to be induced by active bacterial colonization involving type III secretion. We speculate that this form of regulation may have evolved to prevent over activation of the immune system from frequent ingestion of innocuous, non-colonizing, or non-viable bacteria. While additional work is needed to delineate the molecular mechanisms underlying our observations, our findings provide significant novel insight into the immunological adaptation of cockroaches to life in septic environments as well as the factors that regulate bacterial pathogen transmission by these insects. Summary: This study demonstrates that antimicrobial peptide gene expression in the German cockroach gut can be highly specific, responding to type III secretion-dependent colonization processes rather than to general bacterial associated molecular patterns. This finding provides new insight into the immunological adaptation of cockroaches to life in septic environments as well as the factors that regulate bacterial pathogen transmission by these insects.
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影响因子：
2.1
作者：
Nayduch D;Cho H;Joyner C
通讯作者：
Joyner C
美洲大蠊发育可塑性的基因组和功能景观
影响因子：
16.6
作者：
Li, Sheng;Zhu, Shiming;Zhan, Shuai
通讯作者：
Zhan, Shuai
DOI：
10.1073/pnas.0404952102
发表时间：
2005-01-25
影响因子：
11.1
作者：
Choe, KM;Lee, H;Anderson, KV
通讯作者：
Anderson, KV
DOI：
10.1073/pnas.070357597
发表时间：
2000-03-28
影响因子：
11.1
作者：
Basset, A;Khush, RS;Lemaitre, B
通讯作者：
Lemaitre, B
影响因子：
30.5
作者：
Little, TJ;Hultmark, D;Read, AF
通讯作者：
Read, AF