中文摘要：

转座子是宿主基因组的重要组成部分.Ty3/gypsy 反转座子是广泛存在于生物体内的一类反转座子.通过反向PCR（inverse PCR）和基因组步移方法成功地从二化螟体内获得一个具有完整结构的 Ty3/gypsy 反转座子拷贝,命名为Csu-Ty3（GenBank 登录号：KJ191261）.该反转座子拷贝全长4934 bp,在基因组上插入的靶位点（target sit duplications, TSDs）是“AACGT”,两端的长末端重复序列（long terminal repeat,LTR）不完全相同,5′端 LTR 长161 bp,3′端 LTR 长168 bp,两者的一致度为93．5％；在靠近3′端 LTR 处有一段长15 bp 的嘌呤尾（polypurine tract,PPT）序列.经 ORF Finder 分析,Csu-Ty3中包含三个独立的 ORF,从左至右第一个 ORF 编码类似病毒的结构蛋白,称为 GAG 蛋白；第二个 ORF 编码天冬氨酰蛋白酶（aspartic protease,AP）蛋白；第三个 ORF 编码一个多聚蛋白,包含反转录酶（reverse transcriptase,RT）、RNA酶 H（RNase H,RH）以及整合酶（integrase,IN）.Southern 杂交显示二化螟不同地理种群中均有较多的 Csu-Ty3拷贝.在特定基因座位上,对 Csu-Ty3拷贝插入与否的检测结果显示,二化螟不同地理种群中在该位点上均含有 Csu-Ty3拷贝的插入,但在德阳和江津种群中有些个体在该位点上没有检测到 Csu-Ty3拷贝的插入.

英文摘要：

Transposable elements constitute a substantial fraction of host genomes.Ty3/gypsy retrotransposon,one group of LTR retrotransposons,is widespread in different species.By inverse-PCR and genome walking,a novel member of Ty3/gypsy retrotransposons was cloned from Chilo suppressalis .This new member of Ty3/gypsy retrotransposons was named Csu-Ty3 （GenBank accession No.KJ1 9 126 1 ）.The sequence is 4 934 bp in length and integrated into the “AACGT”target site duplications （TSDs）of the genome.There is a pair of non-completely identical long terminal repeats （LTRs）in the Csu-Ty3 retrotransposon.The 5′LTR is 1 6 1 bp in length and the 3′LTR is 1 68 bp,sharing 93？5 % similarities.A polypurine tract （PPT）,1 5 bp in length,is adjacent to the 3′LTR.There are three independent open reading frames （ORFs）in Csu-Ty3.The first ORF encodes a protein which is related to viral structural protein,termed GAG.The second encodes aspartic protease （AP）.The third encodes a polyprotein including a reverse transcriptase （RT）which produces a cDNA copy of the transposon′s RNA,an RNase H （RH）which splits the DNA-RNA hybrid and an integrase （IN ） which inserts the cDNA into the host′s genome.The southern hybridization indicated that there were many Csu-Ty3 copies in different C .suppressalis populations.Flanking PCR results showed that the Csu-Ty3 copy was inserted at the same locus in different populations.At this locus,all the individuals have the Csu-Ty3 copy insertion except some individuals from Deyang and Jiangjin populations.The Csu-Ty3 insertion ratio varied with field populations.