中文摘要：

大部分单股正链RNA病毒的基因组末端含有poly（A）尾，这对病毒基因组RNA的感染性起着非常重要的作用。本研究以猪繁殖与呼吸综合征病毒（PRRSV）感染性克隆pCBC2为平台进行反向遗传操作，通过突变PCR获得poly（A）尾长度分别为0、5、8、9、10、22、35的全长突变体克隆，经体外转录转染MARC-145细胞，观察细胞病变（CPE），对于能产生CPE的突变克隆，抽提细胞上清中的病毒RNA，通过G-Tailing法鉴定子代病毒基因组的poly（A）尾长度。结果表明：1、poly（A）尾影响PRRSV基因组的感染性，且最小长度为10；2、PRRSV基因组poly（A）尾在感染细胞过程中能被修复。

英文摘要：

Poly （A） tails exist in the genomes of many positive single-strand RNA viruses and plays an important role in viral infectivity. In this study, a series of porcine reproductive and respiratory syndrome virus eDNA clones with partial deletion of poly （A） tail were generated through PCR-based mutagenesis based on full-length infectious clone pCBC2. RNAs were obtained by in vitro transcription and transfected into MARC-145 cells. Viral RNAs were extracted from the supematant of cells with noticable cytopathic effect, and the poly （A） tail lengths in progeny virus genomes were identified by G-Tailing method. The results showed that the minimum essential length of the poly （A） is 10; the truncated poly （A） tail in the infectious mutants could be repaired during infection process.