Taking cultivars ‘Dazihulu ’ and ‘Hybrid bottle gourd ’ of Lagenaria siceraria ( Molina ) Standl. as tested materials, RT sequence of LINE retrotransposon in their genomic total DNA was amplified, and alignment, homology analysis and phylogeny analysis of nucleotide sequence of 30 cloning products and their amino acid sequences encoded were carried out. The results show that genomic total DNA of both ‘Dazihulu’ and ‘Hybrid bottle gourd’ includes RT sequence fragment with length about 580 bp. Length of 30 RT nucleotide sequences (Nos. from LsRT1 to LsRT30) of LINE retrotransposon obtained from the two cultivars is 564-599 bp, base number of A, T, G and C is 143-193, 157-205, 104-139 and 83-134, respectively and AT/GC ratio is 1. 29-1. 76, which shows high heterogeneity. The main factors inducing difference in length of RT nucleotide sequence of LINE retrotransposon from L. siceraria are deletion mutation and stop codon mutation. Similarity of 30 RT nucleotide sequences of LINE retrotransposon from L. siceraria is 47. 1%-99. 5%, and that of amino acid sequence encoded is 26. 7%-100. 0%. Based on nucleotide substitution, 30 RT nucleotide sequences of LINE retrotransposon from L. siceraria can be divided into four families, which contains 14, 8, 1 and 7 sequences, respectively. The analysis result on amino acid sequence shows that RT amino acid sequence of LINE retrotransposon from L. siceraria contains 20 conservative amino acid residues and many semi-conservative amino acid residues, and 14 amino acid sequences possess stop codon mutation. Family 1, Family 2 and Family 4 may be the retrotransposon families with transposition activity, and include 8, 3 and 5 RT amino acid sequences without stop codon, respectively. According to phylogenetic tree constructed on RT amino acid sequence of LINE retrotransposon from L. siceraria and other 15 species, there is higher homology in RT amino acid sequence of LINE retrotransposon from L. siceraria with those from Vitis vinifera Linn., Cucumis sativus Linn. and other species. It is suggested that LINE retrotransposon from L. siceraria is a more ancient element, and can be horizontally transferred among genome of L. siceraria and other species.%以瓠瓜[Lagenaria siceraria (Molina) Standl.]品种‘大籽葫芦’(‘Dazihulu’)和‘杂交瓠瓜’(‘Hybrid bottle gourd’)为供试材料,对其基因组总DNA中的LINE逆转座子RT序列进行扩增,并对30个克隆产物的核苷酸序列及其编码的氨基酸序列进行比对、同源性分析和系统进化分析。结果表明：瓠瓜品种‘大籽葫芦’与‘杂交瓠瓜’的基因组总DNA均包含长度约580 bp的RT序列片段。从2个瓠瓜品种中获得的30条LINE逆转座子RT核苷酸序列(编号为LsRT1至LsRT30)长度为564~599 bp,碱基A、T、G和C的数量分别为143~193、157~205、104~139和83~134,AT/GC比为1.29~1.76,表现出高度异质性。缺失突变和终止密码子突变是造成瓠瓜LINE逆转座子RT核苷酸序列长度差异的主要因素。30条瓠瓜LINE逆转座子RT核苷酸序列的相似性为47.1%~99.5%,其编码的氨基酸序列相似性为26.7%~100.0%。根据核苷酸替代值,30条瓠瓜LINE逆转座子RT核苷酸序列可分为4个家族( family),分别包含14、8、1和7条序列。氨基酸序列分析结果显示：瓠瓜LINE逆转座子RT氨基酸序列包含20个保守氨基酸残基和多个半保守氨基酸残基；有14条氨基酸序列具有终止密码子突变。 Family 1、Family 2和Family 4是可能具有转座活性的逆转座子家族,分别包含8、3和5条无终止密码子的RT氨基酸序列。根据瓠瓜与其他15种植物的LINE逆转座子RT氨基酸序列构建的系统进化树,瓠瓜与葡萄( Vitis vinifera Linn.)和黄瓜( Cucumis sativus Linn.)等种类的LINE逆转座子RT氨基酸序列有较高同源性。研究结果表明：瓠瓜LINE逆转座子是一类较古老元件,LINE逆转座子可在瓠瓜与其他种类的基因组间横向传递。
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