Abstract The insect midgut peritrophic membrane (PM) is a functional layer that protects insects against abrasive food particles and microorganism infection. Chitin is an essential component of the PM, and its synthesis is catalyzed by chitin synthase 2 (CHS2). CHS2 plays a unique role in chitin synthesis in the PM and thus represents a potential target for eco-friendly pesticides. The chitin synthase 2 gene (CfCHS2) of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), was identified and evaluated. The full-length open reading frame of CfCHS2 was 4428 nucleotides long, encoding 1475 amino acids. Phylogenetic analysis revealed that CfCHS2 clearly clustered with the group of CHS2 sequences from other insects. Real-time quantitative PCR analysis showed that CfCHS2 was expressed in all developmental stages, with the highest expression level in the adult stage and the lowest in the pupal stage. In the adult stage, CfCHS2 was most highly expressed in the abdomen, followed by the midgut. RNAi assay results showed that the larvae curled up and could not crawl normally after CfCHS2 silencing. The midgut tissue of the larvae subjected to RNAi treatment was observed by tissue section scanner and transmission electron microscope (TEM). The results showed that the PM of the larvae was absent after CfCHS2 gene silencing. These results suggest that CfCHS2 is a potential RNAi target for C. ferrugineus control.

中文翻译：

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锈谷甲虫 Cryptolestes ferrugineus 几丁质合酶 2 基因的鉴定、mRNA 表达及功能分析

摘要 昆虫中肠周营养膜 (PM) 是保护昆虫免受研磨性食物颗粒和微生物感染的功能层。几丁质是 PM 的重要组成部分，其合成由几丁质合酶 2 (CHS2) 催化。CHS2 在 PM 中的几丁质合成中起着独特的作用，因此代表了环保农药的潜在目标。鉴定并评估了锈粒甲虫 Cryptolestes ferrugineus (Stephens) 的几丁质合酶 2 基因 (CfCHS2)。CfCHS2 的全长开放阅读框长 4428 个核苷酸，编码 1475 个氨基酸。系统发育分析表明，CfCHS2 与来自其他昆虫的 CHS2 序列组明显聚类。实时定量 PCR 分析表明 CfCHS2 在所有发育阶段均有表达，成虫期表达量最高，蛹期最低。在成年阶段，CfCHS2 在腹部表达最高，其次是中肠。RNAi 检测结果表明，CfCHS2 沉默后，幼虫蜷缩起来，不能正常爬行。通过组织切片扫描仪和透射电子显微镜（TEM）观察经过RNAi处理的幼虫的中肠组织。结果表明，CfCHS2基因沉默后幼虫的PM不存在。这些结果表明 CfCHS2 是 C.ferrugineus 控制的潜在 RNAi 目标。通过组织切片扫描仪和透射电子显微镜（TEM）观察经过RNAi处理的幼虫的中肠组织。结果表明，CfCHS2基因沉默后幼虫的PM不存在。这些结果表明 CfCHS2 是 C.ferrugineus 控制的潜在 RNAi 目标。通过组织切片扫描仪和透射电子显微镜（TEM）观察经过RNAi处理的幼虫的中肠组织。结果表明，CfCHS2基因沉默后幼虫的PM不存在。这些结果表明 CfCHS2 是 C.ferrugineus 控制的潜在 RNAi 目标。