Bevivino Giulia, Arcà Bruno, Lombardo Fabrizio
Department of Public Health and Infectious Diseases, Sapienza University of Rome, P.le Aldo Moro, 5-00185 Rome, Italy.
Pathogens. 2021 Oct 9;10(10):1300. doi: 10.3390/pathogens10101300.
Salivary glands play a crucial tripartite role in mosquito physiology. First, they secrete factors that greatly facilitate both sugar and blood meal acquisition. Second, the transmission of pathogens (parasites, bacteria and viruses) to the vertebrate host requires both the recognition and invasion of the salivary glands. Third, they produce immune factors that both protect the organ from invading pathogens and are also able to exert their activity in the crop and the midgut when saliva is re-ingested during feeding. Studies on mosquito sialomes have revealed the presence of several female and/or male salivary gland-specific or enriched genes whose function is completely unknown so far. We focused our attention on these orphan genes, and we selected, according to sequence and structural features, a shortlist of 11 candidates with potential antimicrobial properties. Afterwards, using qPCR, we investigated their expression profile at 5 and 24 h after an infectious sugar meal (local challenge) or thoracic microinjection (systemic challenge) of Gram-negative (, EC) or Gram-positive (, SA) bacteria. We observed a general increase in the transcript abundance of our salivary candidates between 5 and 24 h after local challenge. Moreover, transcriptional modulation was determined by the nature of the stimulus, with salivary gland-enriched genes (especially upon SA stimulus) upregulated shortly after the local challenge and later after the systemic challenge. Overall, this work provides one of the first contributions to the understanding of the immune role of mosquito salivary glands. Further characterization of salivary candidates whose expression is modulated by immune challenge may help in the identification of possible novel antimicrobial peptides.
唾液腺在蚊子生理学中发挥着至关重要的三重作用。首先，它们分泌的因子极大地促进了糖分和血液的摄取。其次，病原体（寄生虫、细菌和病毒）向脊椎动物宿主的传播需要唾液腺的识别和侵入。第三，它们产生免疫因子，既能保护该器官免受病原体入侵，又能在进食过程中唾液被重新摄入时，在嗉囊和中肠发挥其活性。对蚊子唾液腺蛋白质组的研究揭示了一些雌性和/或雄性唾液腺特异性或富集基因的存在，但其功能目前完全未知。我们将注意力集中在这些孤儿基因上，并根据序列和结构特征，挑选出了11个具有潜在抗菌特性的候选基因名单。之后，我们使用定量聚合酶链反应（qPCR），研究了在摄入感染性糖餐（局部刺激）或经胸腔显微注射（全身刺激）革兰氏阴性菌（大肠杆菌，EC）或革兰氏阳性菌（金黄色葡萄球菌，SA）后5小时和24小时，这些基因的表达谱。我们观察到，在局部刺激后5小时至24小时之间，我们唾液腺候选基因的转录本丰度普遍增加。此外，转录调节由刺激的性质决定，唾液腺富集基因（尤其是在金黄色葡萄球菌刺激后）在局部刺激后不久上调，在全身刺激后较晚上调。总体而言，这项工作为理解蚊子唾液腺的免疫作用提供了首批贡献之一。对那些表达受免疫刺激调节的唾液腺候选基因进行进一步表征，可能有助于鉴定可能的新型抗菌肽。
