Department of Entomology, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung City 402, Taiwan.
Department of Entomology, National Chung Hsing University, 145 Xingda Rd., South Dist., Taichung City 402, Taiwan.
Pestic Biochem Physiol. 2018 Jun;148:68-73. doi: 10.1016/j.pestbp.2018.03.016. Epub 2018 Mar 28.
The lesser grain borer, Rhyzopertha dominica, which is a primary pest of stored products, breaks up whole grains and makes them susceptible to secondary infestation by other pests. Insecticide application is the main control measure against this borer. A resistant strain of R. dominica against the insecticide, spinosad, was selected in the laboratory. The full-length cDNA of the target site of spinosad, nicotinic acetylcholine receptor subunit α6, from R. dominica (Rdα6) was cloned and analyzed using reverse transcription PCR and rapid amplification of cDNA ends. The complete 2133-bp cDNA contains the open reading frame of 1497 bp encoding a 498-amino-acid protein. There are four predicted transmembrane (TM) regions, and six extracellular ligand-binding sites at the N-terminus, upstream from the first TM in Rdα6. Three mutations have been found in the resistant strain compared with the susceptible one: (1) a 181-bp fragment truncated at the N-terminus, resulting in the appearance of a premature stop codon, (2) one missing bp at the position 997, causing a frame-shift mutation, and (3) an 87-bp fragment truncated in the TM2 region. In addition, real-time quantitative PCR was applied to detect the transcriptional expression of Rdα6 in both the susceptible and resistant strains. The results indicated that the expression of Rdα6 was significantly lower in then resistant strain than in susceptible one. In conclusion, mutation of Rdα6 may cause R. dominica resistant to spinosad due to target site insensitivity.
米象，一种主要的仓储害虫，会破坏完整的谷物，使它们容易受到其他害虫的二次侵害。杀虫剂的应用是防治这种蛀虫的主要措施。在实验室中，选择了对杀虫剂多杀菌素具有抗性的米象品系。使用反转录 PCR 和快速扩增 cDNA 末端技术，从米象中克隆并分析了多杀菌素的靶标位点烟碱型乙酰胆碱受体亚基α6（Rdα6）的全长 cDNA。完整的 2133bp cDNA 包含 1497bp 的开放阅读框，编码 498 个氨基酸的蛋白质。在 Rdα6 的 N 端，有四个预测的跨膜（TM）区域和六个细胞外配体结合位点。与敏感品系相比，抗性品系发现了三个突变：（1）N 端截断的 181bp 片段，导致出现过早的终止密码子，（2）位置 997 缺失一个 bp，导致移码突变，（3）TM2 区域截断的 87bp 片段。此外，还应用实时定量 PCR 检测 Rdα6 在敏感和抗性品系中的转录表达。结果表明，Rdα6 在抗性品系中的表达明显低于敏感品系。总之，Rdα6 的突变可能导致米象对多杀菌素产生抗性，这是由于靶标部位不敏感所致。
