Karasev A V, Nikolaeva O V, Mushegian A R, Lee R F, Dawson W O
University of Florida, Citrus Research and Education Center, Lake Alfred 33850-2299, USA.
Virology. 1996 Jul 1;221(1):199-207. doi: 10.1006/viro.1996.0366.
The 3'-terminal half of the beet yellow stunt virus (BYSV) genome 10,545 nt, has been cloned and sequenced. The sequenced portion of the BYSV genome encompasses 10 open reading frames (ORFs) and 241 nt of the 3' untranslated region. The sequence spans, in the 5' to 3' direction, the C-terminal region of the replication-associated polyprotein gene (ORF 1a) which includes the set of motifs typical of helicases (HEL), the entire 53-kDa polymerase (RdRp) gene (ORF 1b), and genes encoding 30-kDa (ORF 2), 6-kDa (ORF 3), 66-kDa (ORF 4), 61-kDa (ORF 5), 25-kDa (ORF 6), 23.7-kDa (coat protein, CP) (ORF 7), 18-kDa (ORF 8), and 22-kDa (ORF 9) proteins. The double-stranded RNA "replicative form" of the BYSV was demonstrated to have a nontemplate G residue at the 3' terminus of the (+) strand. The RdRp of BYSV is presumably expressed via a +1 ribosomal frameshift. The five-gene module conserved among closteroviruses was identified in BYSV; it includes a gene array coding for a 6-kDa small hydrophobic protein, a 66-kDa homolog of the cellular HSP70 heat shock proteins, a 61-kDa protein, and a 25-kDa diverged copy of the CP followed by the CP gene itself. Phylogenetic analysis of the replication-associated HEL and RdRp domains as well as proteins from the five-gene module demonstrated the closest relationship between BYSV and two other closteroviruses, beet yellows (BYV) and citrus tristeza (CTV) viruses. Like CTV, the BYSV genome contains a 30-kDa protein gene between the RdRp and the 6-kDa protein genes, and like BYV it has only two genes downstream of the CP gene. The organization of the BYSV genome appears to be intermediate between BYV and CTV, which suggests that these three viruses might represent three distinct but probably close stages in the closterovirus evolution.
甜菜黄矮病毒（BYSV）基因组10545个核苷酸的3'末端一半已被克隆并测序。BYSV基因组的测序部分包括10个开放阅读框（ORF）和3'非翻译区的241个核苷酸。该序列在5'至3'方向上跨越复制相关多聚蛋白基因（ORF 1a）的C末端区域，其中包括解旋酶（HEL）典型的基序集、整个53 kDa聚合酶（RdRp）基因（ORF 1b），以及编码30 kDa（ORF 2）、6 kDa（ORF 3）、66 kDa（ORF 4）、61 kDa（ORF 5）、25 kDa（ORF 6）、23.7 kDa（外壳蛋白，CP）（ORF 7）、18 kDa（ORF 8）和22 kDa（ORF 9）蛋白的基因。BYSV的双链RNA“复制形式”被证明在（+）链的3'末端有一个非模板G残基。BYSV的RdRp可能通过+1核糖体移码表达。在BYSV中鉴定出了在长线形病毒中保守的五基因模块；它包括一个编码6 kDa小疏水蛋白的基因阵列、细胞HSP70热休克蛋白的66 kDa同源物、一个61 kDa蛋白、CP的一个25 kDa分化拷贝，随后是CP基因本身。对复制相关的HEL和RdRp结构域以及来自五基因模块的蛋白质进行系统发育分析，结果表明BYSV与另外两种长线形病毒甜菜黄化病毒（BYV）和柑橘衰退病毒（CTV）关系最为密切。与CTV一样，BYSV基因组在RdRp和6 kDa蛋白基因之间含有一个30 kDa蛋白基因，与BYV一样，它在CP基因下游只有两个基因。BYSV基因组的组织形式似乎介于BYV和CTV之间，这表明这三种病毒可能代表了长线形病毒进化过程中的三个不同但可能相近的阶段。
