中文摘要：

为分析2002-2007年分离的鸭源弱毒新城疫病毒（Newcastle disease virus,NDV）磷蛋白（P）基因的分子特征,以及在新城疫病毒演化过程中所起的作用,采用RT-PCR方法扩增NDV弱毒分离株的P基因,进行测序,并应用生物信息学软件（SNAP和CODEML）研究了作用于NDV P基因的选择压力。根据P基因序列的遗传发生分析表明,NDV I类（Class I）2型毒株与德国鸭源毒株DE/R49-99和美国株亲缘关系较近,而3b型毒株与其他I类病毒遗传关系较远,具有地区特色,形成一个独特的分支;NDV II类（Class II）中基因Ib型与中国广泛使用的基因I型疫苗毒Qeensland V4（QV4）以及I型代表株亲缘关系较远。生物信息学软件分析表明,P基因不同片段受到正选择压力的作用不一样,P基因的两端受到负选择压力的作用不易发生变异,而中间（aa62~113和137~198）片段多个位点受到正选择压力的作用。可见,I类病毒中3b具有地域特色,不同基因型P蛋白之间变异较大,而且P蛋白不同位置变异不均匀。

英文摘要：

Eleven avirulent Newcastle disease viruses（NDVs） were isolated from ducks in China from 2002 to 2007.Phosphoprotein（P） genes of these NDVs were amplified by RT-PCR and sequenced.The P gene sequences were analyzed using bioinformatic software（SNAP and CODEML） to examine genetic variability and their effect on virus evolution.The P gene sequences of twenty eight NDV reference strains in GenBank were also included for comparison in the present study.Phylogenetic analysis of the P gene indicated that Class I genotype 2 Chinese viruses were closely related to some European and American viruses and Class I genotype 3b viruses formed a separate branch,which geographically distributed within China only.Class II genotype Ib viruses diverged from the representative strains of genotype I and the vaccine virus Queensland V4,the latter is extensively used in China.The bioinformatic analysis revealed graphic patterns of the dS and dN values and confirmed the prevalence of positive selection at terminal regions of P proteins（aa 62-113 and 137-198）.Class I genotype 3b virus was unique to China.The P protein of different genotypes was most highly variable and the variability was presented in a few localized regions under negative and positive selections.