Abstract

Insect innate immunity is initiated by the special recognition and binding of the foreign pathogens, which is accomplished by the pattern recognition receptors (PRRs). As an important type of PRRs, C-type lectins (CTLs) play various roles in insect innate immunity, including pathogen recognition, stimulation of prophenoloxidase, regulation of cellular immunity and so on. In this study, we have cloned the full-length cDNA of a CTL gene named CTL-S6 from the silkworm, Bombyx mori. The open reading frame (ORF) of B. mori CTL-S6 encodes 378 amino acids, which contain a secretion signal peptide. The mRNA of CTL-S6 exhibited the highest transcriptional level in the midgut. Its transcriptional level increased dramatically in fat body and hemocytes upon Escherichia coli or Micrococcus luteus challenge. Purified recombinant CTL-S6 could bind to bacterial cell wall components, including peptidoglycan (PGN, from Bacillus subtilis) and lipopolysaccharide (LPS, from E. coli 0111:B4), and recombinant CTL-S6 was involved in the encapsulation and melanization of hemocytes. Furthermore, the addition of recombinant CTL-S6 to the hemolymph of silkworm resulted in a significant increase in phenoloxidase activity. Overall, our results indicated that B. mori CTL-S6 may serve as a PRR for the recognition of foreign pathogens, prophenoloxidase pathway stimulation and involvement in the innate immunity.

中文翻译：

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模式识别受体C型凝集素-S6（CTL-S6）参与家蚕的免疫反应（鳞翅目：家蚕）

摘要

昆虫的先天免疫是通过外来病原体的特殊识别和结合而启动的，这是通过模式识别受体（PRR）实现的。作为PRR的重要类型，C型凝集素（CTL）在昆虫的先天免疫中起多种作用，包括病原体识别，刺激酚氧化酶原，调节细胞免疫等。在这项研究中，我们克隆了命名为CTL基因的全长cDNA CTL-S6从家蚕，家蚕。桑树芽孢杆菌CTL-S6的开放阅读框（ORF）编码378个氨基酸，其中包含分泌信号肽。CTL-S6的mRNA在中肠表现出最高的转录水平。在大肠杆菌或黄球菌攻击后，其在脂肪体和血细胞中的转录水平急剧增加。纯化的重组CTL-S6可以结合细菌细胞壁成分，包括肽聚糖（PGN，来自枯草芽孢杆菌）和脂多糖（LPS，来自大肠杆菌0111：B4），重组CTL-S6参与血细胞的封装和黑色素化。此外，向家蚕的血淋巴中添加重组CTL-S6导致酚氧化酶活性显着增加。总体而言，我们的结果表明桑蚕 CTL-S6可作为PRR，用于识别外来病原体，酚氧化酶原途径刺激和参与先天免疫。