甜菜夜蛾类钙粘蛋白基因全长cDNA的克隆及序列分析

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。

Cloning and sequence analysis of the cadherin-like protein gene in beet armyworm, Spodoptera exigua

The cadherin-like proteins, located in the brush border membrane vesicles （BBMV） of the insect midgut, are major receptors of Bacillus thuringiensis insecticidal crystal protein. The complete eDNA sequence of the cadherin-like protein gene in the beet armyworm, Spodoptera exigua （Htibner） was amplified using RT-PCR and RACE techniques. The full eDNA sequence （named as SeCAD, GenBank accession no. HQ647122） is 5 582 bp in length, encoding 1 739 amino acid residues. The deduced amino acid sequence shows typical characteristics of the known insect eadherin proteins, including a signal peptide, a proprotein region, eleven cadherin repeats, a membrane-proximal region, a transmembrane region and a cytoplasmic region. The predicted molecular weight and isoelectric point are 196. 447 ku and 4.47, respectively. The cadherin-like protein from S. exigua shows a close relationship to cadherin proteins from Sesamia inferens, S. nonagrioides, Heliothis virescens and Helicoverpa assulta, with amino acid identity of 61.28% , 60. 34%, 60. 14% and 60. 08% , respectively. These results can provide a basis for revealing the insecticidal mechanism of Bt in S. exigua, and the resistance mechanism of S. exigua to Bt.