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昆虫中肠膜上的类钙粘蛋白(cadherin-like protein)是Bt毒素的一类重要受体,它与Bt毒素对昆虫的杀虫作用机制以及昆虫对Bt毒素的抗性等密切相关。本研究根据已报道的其它昆虫的类钙粘蛋白基因的保守区设计简并引物,应用RT-PCR和RACE技术克隆了迁飞性重要害虫甜菜夜蛾Spodoptera exigua(Hübner)类钙粘蛋白基因全长cDNA序列(命名为SeCAD,GenBank登录号为HQ647122),全长5582bp,编码1739个氨基酸,推导的氨基酸序列包括1个信号肽、1个前蛋白区、11个钙粘蛋白重复、1个近膜区、1个跨膜区和1个胞质区。预测的分子量和等电点分别为196.447ku和4.47。该蛋白与同科的大螟Sesamia inferens、蛀茎夜蛾S.nonagrioides、烟芽夜蛾Heliothi svirescens、烟夜蛾Helicover paassulta亲缘关系更近,氨基酸序列一致性分别为61.28%、60.34%、60.14%、60.08%。这些结果对于揭示转Bt基因作物对非靶标、迁飞性甜菜夜蛾的杀虫作用机制以及评价其潜在的对Bt毒素抗性机制等奠定了基础。
The cadherin-like protein in insect midgut membrane is a kind of important receptor of Bt toxin, which is closely related to insecticidal mechanism of Bt toxin and insect resistance to Bt toxin. In this study, degenerate primers were designed based on the reported conserved regions of other cadherin-like cadherin genes. The cadherin gene of Spodoptera exigua (Hübner), a major migratory insect pest, was cloned by RT-PCR and RACE techniques The full-length cDNA sequence (named SeCAD, GenBank Accession No. HQ647122) is 5582bp in length and encodes a protein of 1739 amino acids. The deduced amino acid sequence consists of 1 signal peptide, 1 preprotein region, 11 cadherin repeats and 1 near Membrane zone, a transmembrane zone and a cytoplasmic zone. The predicted molecular weights and isoelectric points were 196.447ku and 4.47, respectively. The protein was more closely related to Sesamia inferens, S.nonagrioides, Heliothi svirescens and Helicoverpaassulta in the same family, and the amino acid sequence identities were 61.28%, 60.34% and 60.14% respectively, , 60.08%. These results lay the foundation for revealing the mechanism of insecticidal action of transgenic Bt crops on non-target and migrating beet armyworm and evaluating their potential mechanism of resistance to Bt toxin.