甘蔗花叶病毒复制酶基因的克隆及序列分析

Cloning and Sequence Analysis of Replicase Genes of Sugarcane Mosaic Virus

以甘蔗花叶病毒（SCMV）福建分离物（FJ）的总RNA为模板，用RT—PCR方法扩增了含有复制酶（NIb）基因的DNA片段，将其克隆到质粒pGM—T载体上并进行了序列分析。结果表明，NIb基因由1563个碱基组成，编码521个氨基酸并含有高度保守序列GDD。NIa／NIb和NIb／CP交界处的蛋白酶切割位点分别为Q／C和Q／A。与国外报道的SCMV亚组几个株系分离物相比，NIb基因（福建分离物）的核苷酸和氨基酸序列同源性分别为57．8％～86．9％和60．9％～95．2％，其中与SCMV—SA株系的核苷酸及氨基酸序列同源性则高达86．9％和95．2％。

The NIb coding region of sugarcane mosaic virus （SCMV） from Fujian was amplified from the extracted plant total RNA by using RT-PCR, and cloned into the pGM-T vector and sequenced. The result indicated that the NIb coding region comprised 1563 nucleotides and encoded a putative protein of 521 amino acids containing the consensus motif GDD. The protease cleavage sites between the NIa/NIb and NIb/coat protein were found to be Q/C and Q/A respectively. The nucleotide and the putative amino acid of replicase were compared with the other isolates or stain of SCMV subgroup, it shares 57.8%-86.9% and 60.9%-95.2% homology in nucleotide and the putative amino acid sequence respectively. The NIb sequence was most similar to SCMV-SA with identities of 86.9% and 95.2 % at the nucleotide and amino acid levels respectively.