鸡肾型IBV山东分离株核蛋白基因的遗传变异分析

Genetic variations of nucleocapsid gene of infectious bronchitis nephritis virus strains isolated in Shandong province of China

应用RT-PCR方法扩增到了山东省2006—2007年分离的10株肾型IBV核蛋白(N)基因片段,并将其进行了克隆、序列测定及分析。结果发现,10株肾型IBV分离株核蛋白基因均含有1个长1230bp的ORF,编码由409个氨基酸残基组成的多肽,未发现碱基的插入和缺失。与GenBank中的20个IBV参考毒株核蛋白基因序列进行比较和分析,发现10株肾型IBV分离株主要分布于2个群中。第Ⅰ群与弱毒疫苗株H120和参考毒株D41、D1466的亲缘关系较近,第Ⅱ群与参考毒株LX4、GDS14的亲缘关系较近。对核蛋白基因及其局部功能区序列比较发现,山东分离株与H120疫苗株核蛋白相比存在广泛的氨基酸变异,以点突变为主,突变位点无明显规律性。

Nucleocapsid protein （N protein） genes of ten IBV strains isolated in Shandong province of China between 2006 and 2007 were amplified by reverse transcriptase polymerase chain reaction （RT-PCR）, and then cloned, sequenced and compared with 20 IBV reference strains. The results showed that all of the N genes of the ten isolates were composed of 1 230 nucleotides,encoding a polypeptide of 409 amino acid residues. Deletion and insertion were not found in the N genes of the ten isolates. Phylogenetic tree based on amino acid sequences of N genes from ten IBV isolates and 20 reference IBV strains showed that the ten isolates were classified into two clusters. Isolates in group Ⅰ had close relationship with the traditional IBV vaccine strains H120 and reference strains D41 and D1466. I- solates in group lI had close relationship with the reference strains LX4 and GDS14. In addition, compared with the H120 vaccine strain,it was found that point mutations inducing the amino acid substitutions were common in N genes of the ten isolates. Mutational site did not show obvious regularity.