Xenorhabdus nematophila BP品系xptB1基因的克隆和序列分析

采用PCR方法,从该室构建的Xenorhabdus nematophila BP品系粘粒文库的一个对棉铃虫有强口服杀虫活性的粘粒cos83中扩增出全长的xptB1基因,将扩增片段回收纯化后,连接到pMD-18T载体,转化大肠杆菌TG1后进行序列测定和分析。结果显示,该基因全长为3051bp,编码1016个氨基酸,其编码的毒素BP XptB1与X.nematophila PMF1296品系的XptB1的氨基酸序列同源性平均为95.8%,两侧高度一致,中间第607—738位差异明显。结构分析显示,两者在跨膜区,α螺旋等方面也有差异。BP XptB1与Photorhabdus luminescens的TccC毒素,Serratia entomophila的SepC,以及Yersinia pseudotubercusis和Y.pestis等的杀虫毒素均有58%以上的同源性。分析结果预示了XptB1可能是一个杀虫毒素。

Cloning and Sequence Analysis of an xptB1 Gene from Xenorhabdus nematophila BP Strain

A complete xptB1 gene was amplified by PCR from an insecticidal clone from the cosmid library of Xenorhabdus nematophila BP strain.The amplified DNA fragment was ligated to vector pMD18-T,transformed to E.coli TG1 and then sequenced and analyzed.The results showed that the xptB1 of X.nematophila BP has a length of 3051bp,which encodes 1016 amino acids.The amino acid sequence of BP XptB1 has an average similarity of 95.8% to PMF1296 XptB1,a homology toxin from another strain of X.nematophilua,with two terminals highly identical to while the region from 607 to 738 amino acids different significantly from each other.Comparison on secondary structure of BP XptB1 and PMF1296 XptB1 showed some differences on potential trans-membrane segments and alpha helix.BP XptB1 has more than 58% identical to the following insecticidal toxins:TccC toxins from Photorhabdus luminescens,SepC from Serratia entomophila;and toxins from Yersinia pseudotubercusis and Yersinia pestis,respectively.These result showed that the BP XptB1 may be an insecticidal toxin.