BACKGROUNDBactrocera dorsalis (Diptera: Tephritidae) is a highly adaptable invasive pest that causes significant economic losses. Long‐term chemical control strategies have led to high levels of insecticide resistance and severe environmental risks. C‐type lectins (CTLs), key pattern recognition receptors in insect innate immunity, are named for their calcium‐dependent carbohydrate recognition domains (CRDs) and they play a critical role in detecting and binding to foreign pathogens. This study aims to identify B. dorsalis CTLs (BdCTLs) and investigate their roles in pathogen defense.RESULTSA total of 42 BdCTL genes were identified. Based on the number of CRDs, 36 genes were classified into the S subfamily, while the remaining six were assigned to the X subfamily. Spatio‐temporal expression analysis by qPCR revealed that BdCTL genes were expressed throughout all developmental stages with a higher expression observed in the midgut, Malpighian tubules, and fat body. The expression levels of BdCTL‐S4, BdCTL‐S12, and BdCTL‐S31 were significantly upregulated under the infection of the entomopathogenic fungus Beauveria bassiana. Notably, BdCTL‐S12 also exhibited upregulated expression patterns in response to four different pathogens bacteria with sustained expression over time. Using RNA interference (RNAi), we successfully knocked down BdCTL‐S12 expression, achieving a silencing efficiency of 68%. Survival assays demonstrated a 10–30% reduction in the survival rate of B. dorsalis after pathogen infection following dsRNA injection compared to the control group. Further in vitro experiments confirmed that BdCTL‐S12 can agglutinate and bind to pathogens in a calcium‐dependent manner. This binding was competitively inhibited by polysaccharides, underscoring a key functional mechanism of BdCTL‐S12 in pathogen recognition.CONCLUSIONIn summary, we identified 42 BdCTLs and demonstrated that BdCTL‐S12 is critical for pathogen recognition and immune defense in B. dorsalis. These results advance our understanding of the molecular mechanisms underlying B. dorsalis immunity. Specifically, elucidating the role of CTLs may facilitate the development of microbial‐based biological control strategies (e.g., entomopathogenic fungi or bacteria) against this invasive pest. Additionally, RNAi‐mediated knockdown of CTL‐encoding genes could weaken the immune system of Bactrocera flies, increasing their susceptibility to microbial infections and thereby enhancing the effectiveness of biological control. © 2025 Society of Chemical Industry.

中文翻译：

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Bactrocera dorsalis 中 C 型凝集素的基因组鉴定和广谱病原体识别 BdCTL-S12 的功能表征

背景 Bactrocera dorsalis（双翅目：Tephritidae）是一种适应性很强的入侵性害虫，会造成重大经济损失。长期的化学控制策略导致了高水平的杀虫剂耐药性和严重的环境风险。C 型凝集素 （CTL） 是昆虫先天免疫中的关键模式识别受体，以其钙依赖性碳水化合物识别结构域 （CRD） 命名，它们在检测和结合外来病原体方面起关键作用。本研究旨在鉴定 B. dorsalis CTLs （BdCTLs） 并研究它们在病原体防御中的作用。结果共鉴定出 42 个 BdCTL 基因。根据 CRD 的数量，36 个基因被归入 S 亚家族，而其余 6 个基因被归入 X 亚家族。通过 qPCR 进行的时空表达分析显示，BdCTL 基因在所有发育阶段都表达，其中在中肠、马氏小管和脂肪体中表达较高。在昆虫病原真菌 Beauveria bassiana 感染下，BdCTL-S4 、 BdCTL-S12 和 BdCTL-S31 的表达水平显著上调。值得注意的是，BdCTL-S12 还表现出响应四种不同病原体细菌的上调表达模式，并随着时间的推移持续表达。使用 RNA 干扰 （RNAi），我们成功敲低了 BdCTL-S12 表达，实现了 68% 的沉默效率。存活试验表明，与对照组相比，dsRNA 注射后病原体感染后 B. dorsalis 的存活率降低了 10-30%。进一步的体外实验证实，BdCTL-S12 可以钙依赖性方式凝集并与病原体结合。 这种结合被多糖竞争性抑制，强调了 BdCTL-S12 在病原体识别中的关键功能机制。结论综上所述，我们鉴定了 42 个 BdCTLs，并证明 BdCTL-S12 对 B. dback 的病原体识别和免疫防御至关重要。这些结果促进了我们对 B. dorsalis 免疫的分子机制的理解。具体来说，阐明 CLL 的作用可能有助于开发针对这种入侵性害虫的基于微生物的生物控制策略（例如，昆虫病原真菌或细菌）。此外，RNAi 介导的 CTL 编码基因敲低可以削弱 Bactrocera 果蝇的免疫系统，增加它们对微生物感染的敏感性，从而提高生物防治的有效性。© 2025 化工学会.