甘蔗花叶病毒3’末端基因的克隆及外壳蛋白序列分析比较

Cloning of 3'-terminal Part of Sugarcane Mosaic Virus RNA and Sequence Comparison of CP Gene Between Chinese Isolate and Other Strains of SCMV

选取我国SCMV优势株系A株系的分离物SCMV CA为材料 ,经过病毒和病毒RNA的提纯 ,反转录获得病毒cDNA ,并克隆到载体 pUC19的SmaI位点上 ,筛选得到多个重组质粒。选取其中一个克隆SCMV CA5 4进行测序 ,得到一个全长为 12 96bp的核苷酸序列。这段序列由一个长为 10 44bp的开放阅读框架 (ORF)和一个长 2 79bp的 3’末端非编码区序列 ( 3’ UTR)及 poly(A)尾巴组成。这个ORF包括病毒完整的外壳蛋白 (CP)及部分核内含体蛋白b(NIb)基因序列。将所得序列同已知SCMV亚组中各株系分离物的核苷酸和氨基酸进行同源性比较 ,结果表明该序列与其它株系分离物CP核苷酸序列的同源性介于 6 3.7%～ 77.6 %之间 ,氨基酸的同源性介于 6 4%～ 89%之间。根据马铃薯Y病毒属的序列同源性划分标准 ,SCMV CA与其它株系或分离物的同源性关系均介于种与株系划分标准之间。

SCMV CA, an isolate of the dominant A strain in China continent was propagated on sweet maize and purified. Cloned cDNAs representing more than 0.8kb of the 3' termini were obtained after a reverse transcription and ligation to pUC19 in Sma I site using an oligo(dT) primer. One clone named SCMV CA54 was sequenced and the length of the SCMV CA54 was 1296 bp. The sequence covered the 3' untranslated region (3' UTR), coat protein (CP) and part of the nuclear inclusion b (NIb) genes of the virus. The nucleotide and deduced amino acid sequence in the CP gene between Chinese isolate SCMV CA and other isolates or strains of SCMV subgroup were compared. Results showed that the homology of nucleotide sequence in CP gene between SCMV CA and other isolates or strains of SCMV subgroup ranged from 63.7% to 77.6%, and amino acid sequence from 64% to 89%. This homology degree lies between the range for distinct viruses and that between related strains of potyviruses, arguing that the Chinese isolate might represent a distinct virus.