中文摘要：

【目的】克隆Ty3-gypsy类反转录转座子反转录酶（RT）序列并分析其特性,为火龙果遗传变异和进化研究提供新的信息。【方法】根据Ty3-gypsy类反转录转座子RT保守区设计简并引物,从红肉和白肉火龙果及其突变体中扩增出430 bp左右的目标片段,回收、克隆、测序获得RT序列,并进行生物信息学分析;采用RT-PCR检测其转录活性。【结果】共获得82条RT序列,其中有55条序列发生终止密码子突变,5条序列发生移码突变;经RT序列对比,火龙果与水稻、拟南芥有较高的同源性;3条RT序列具有转录活性。【结论】火龙果Ty3-gypsy类反转录转座子RT序列具有高度异质性,部分序列具有转录活性,与其他物种存在反转录转座子的横向传递。

英文摘要：

【Objective】In order to provide a fundamental clue for genetic evolution and variation mecha-nisms in Hylocereus undatus, reverse transcriptase（RT） sequences of Ty3- gypsy retrotransposon werecloned and analyzed in the genome of pitaya.【Methods】Using degenerate oligonucleotide primers basedon the conserved domains of the Ty3-gypsy LTR retrotransposon RT sequence, 430 bp fragment was am-plified through a polymerase chain reaction（PCR） from the genomic DNA of red-flesh pitaya（‘Xinhon-glong＇）, white-flesh pitaya（‘Baiyulong＇） plants and their mutants. The amplicons were cloned, then se-quenced and analyzed. Sequence homology queries for nucleotide and deduced amino acid sequences ofTy3-gypsy LTR retrotransposon RT sequences were performed using BLASTn and BLASTx（https：//blast.ncbi.nlm.nih.gov/Blast.cgi）, respectively. Multiple sequence alignments were conducted using the ClustalW program. Phylogenetic trees were generated using MEGA 6.06 software by p-distance and neighbor-joining methods by 1 000 bootstrap replications. Special primers were designed at the basis of all RT se-quences of pitaya using Primer Premier 5.0 software, and were employed to detect their transcriptional ac-tivities from the plants grown normally in the field and the tissue culture seedlings obtained by reversetranscription PCR（RT-PCR）. RT-PCR was carried out with the corresponding c DNA, which was reversetranscribed from the total RNA of the test samples（‘Zihonglong＇）. The PCR products were electropho-resed in 1% agarose gel and observed under UV light after staining with Goldview.【Results】The PCR am-plification with degenerate primers yielded an expected 430 bp fragment. The fragment within this bandwas recovered and sequenced. Totally, 31 RT sequences from the red-flesh type and 51 from the white-flesh type were obtained, which were named HURT. Sequences ranged in length from 431 bp to 444 bp,most of which were AT-rich, with AT content of 48.6%-63.0%. When the nucleotide sequences of the R