C‐type lectins are one of the pattern‐recognition proteins involved in innate immunity in invertebrates. Although there are 16 C‐type lectin genes that have been identified in the genome of Tribolium castaneum, their functions and mechanisms in innate immunity remain unknown. Here, we identified one C‐type lectin orthologue, TcCTL6 (TC003708), by sequencing random clones from the cDNA library of the coleopteran beetle, T. castaneum. TcCTL6 contains a 654 bp open reading frame encoding a protein of 217 amino acids that includes a single carbohydrate‐recognition domain. The expression of TcCTL6 was significantly induced by Escherichia coli, Staphylococcus aureus and stimulation with carbohydrates, including lipopolysaccharide and peptidoglycan. A binding assay suggested that the recombinant TcCTL6 not only bound to lipopolysaccharide and peptidoglycan but also bound to Gram‐positive (S. aureus, Bacillus subtilis and Bacillus thuringiensis) and Gram‐negative bacteria (E. coli and Pseudomonas aeruginosa) in the presence of calcium ions. Furthermore, when TcCTL6 was knocked down by RNA interference, four antimicrobial peptides (attacin1, attacin2, coleoptericin1 and coleoptericin2) were significantly decreased. These results demonstrate that TcCTL6 plays a vital role in the immune response towards pathogen infection by influencing the expression of antimicrobial peptides and the agglutination of bacteria in the presence of calcium ions in T. castaneum.

中文翻译：

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具有单个碳水化合物识别域的C型凝集素，参与了Tribolium castaneum的先天免疫应答。

C型凝集素是无脊椎动物固有免疫中涉及的模式识别蛋白之一。尽管在Tribolium castaneum基因组中已经鉴定出16种C型凝集素基因，但它们在先天免疫中的功能和机制仍然未知。这里，我们确定了一个C型凝集素直向同源物，TcCTL6（TC003708），通过从鞘翅目甲虫，cDNA文库测序随机克隆赤拟谷盗。TcCTL6包含一个654 bp的开放阅读框，编码一个217个氨基酸的蛋白质，其中包含一个碳水化合物识别结构域。TcCTL6的表达被大肠杆菌，金黄色葡萄球菌明显诱导。并用碳水化合物刺激，包括脂多糖和肽聚糖。结合试验表明，重组TcCTL6不仅可以与脂多糖和肽聚糖结合，而且还可以与革兰氏阳性菌（金黄色葡萄球菌，枯草芽孢杆菌和苏云金芽孢杆菌）和革兰氏阴性菌（大肠杆菌和铜绿假单胞菌）结合。钙离子。此外，当TcCTL6被RNA干扰击倒时，四个抗菌肽（attacin1，attacin2，coleoptericin1和coleoptericin2）明显减少。这些结果表明，TcCTL6在钙锥T中存在钙离子的情况下，通过影响抗菌肽的表达和细菌的凝集作用，在病原体感染的免疫反应中起着重要作用。