According to the genomic sequence of foreign four PLRV isolates, three pairs of specific primer were designed and synthesized.The cDNA of the ORF2a gene of PLRV-Ch was synthesized by reverse transcription and followed by Polymerase Chain Reaction amplication.The synthesized 3′and 5′cDNA fragment of the PLRV-Ch ORF2a gene were inserted into pUC19 and cloned in E.coli JM109 and were sequenced respectively.The middle cDNA fragment were directly sequenced.The homology of nucleotide sequence of PLRV-Ch compared with PLRV-S (Scotland,UK),PLRV-N(Netherlands),PLRV-A(Australia) and PLRV-C(Canada) were 98.96%、98.70%、94.79%、97.5%,the homology of putative amino acid sequence are 97.97%、97.97%、89.69%、95.94%.In 3′region of ORF2a gene a slippery sequence for-1 frameshift and its downstream “stem-loop"or“pseudoknot"and upstream nucleotide sequence repeats were found.Authors suggested that the nucleotide repeat sequences charateristic for PLRV could form a tight successively folded complementary double stranded regions and hairpins.This structure possibly has something to do with-1 frameshift.The amino acid sequence of C terminus region of 70kD protein translated by motif Ⅳ has a protease charateristic motif and a helicase motif Ⅳ.The amino acid sequence of polypeptide translated by ORF2a gene undergoing frameshift has a single-stranded nucleic acid binding protein-like charateristic motif.
