Liou M R, Chen Y R, Liou R F
Department of Plant Pathology and Microbiology, National Taiwan University, Taipei, Taiwan.
Arch Virol. 2004 May;149(5):1037-43. doi: 10.1007/s00705-003-0251-1. Epub 2003 Dec 23.
The complete nucleotide sequence of a strain of Cactus virus X (CVX-Hu) isolated from Hylocereus undatus (Cactaceae) has been determined. Excluding the poly(A) tail, the sequence is 6614 nucleotides in length and contains seven open reading frames (ORFs). The genome organization of CVX is similar to that of other potexviruses. ORF1 encodes the putative viral replicase with conserved methyltransferase, helicase, and polymerase motifs. Within ORF1, two other ORFs were located separately in the +2 reading frame, we call these ORF6 and ORF7. ORF2, 3, and 4, which form the "triple gene block" characteristic of the potexviruses, encode proteins with molecular mass of 25, 12, and 7 KDa, respectively. ORF5 encodes the coat protein with an estimated molecular mass of 24 KDa. Sequence analysis indicated that proteins encoded by ORF1-5 display certain degree of homology to the corresponding proteins of other potexviruses. Putative product of ORF6, however, shows no significant similarity to those of other potexviruses. Phylogenetic analyses based on the replicase (the methyltransferase, helicase, and polymerase domains) and coat protein demonstrated a closer relationship of CVX with Bamboo mosaic virus, Cassava common mosaic virus, Foxtail mosaic virus, Papaya mosaic virus, and Plantago asiatica mosaic virus.
已测定从量天尺（仙人掌科）中分离出的一株仙人掌X病毒（CVX-Hu）的完整核苷酸序列。除去聚腺苷酸尾，该序列长度为6614个核苷酸，包含7个开放阅读框（ORF）。CVX的基因组结构与其他马铃薯X病毒相似。ORF1编码具有保守甲基转移酶、解旋酶和聚合酶基序的假定病毒复制酶。在ORF1内，另外两个ORF分别位于+2阅读框中，我们将其称为ORF6和ORF7。形成马铃薯X病毒“三联基因块”特征的ORF2、3和4分别编码分子量为25、12和7 kDa的蛋白质。ORF5编码估计分子量为24 kDa的外壳蛋白。序列分析表明，ORF1-5编码的蛋白质与其他马铃薯X病毒的相应蛋白质显示出一定程度的同源性。然而，ORF6的推定产物与其他马铃薯X病毒的推定产物没有显著相似性。基于复制酶（甲基转移酶、解旋酶和聚合酶结构域）和外壳蛋白的系统发育分析表明，CVX与竹花叶病毒、木薯普通花叶病毒、狗尾草花叶病毒、木瓜花叶病毒和车前草花叶病毒的关系更为密切。
