Sunter G, Hartitz M D, Hormuzdi S G, Brough C L, Bisaro D M
Biotechnology Center, Ohio State University, Columbus 43210.
Virology. 1990 Nov;179(1):69-77. doi: 10.1016/0042-6822(90)90275-v.
Tomato golden mosaic virus (TGMV) is a geminivirus whose genome is divided between two DNA components, designated A and B. The TGMV genome contains six open reading frames (ORFs) which can encode proteins of greater than 10 kDa. We have used a protoplast transfection system to determine the effects of viral proteins, as defined by these ORFs, on the accumulation of viral DNA in infected cells. The accumulation of cost protein was also examined in leaf discs. Our results indicate that mutations in ORFs AR1 and AL2 do not affect viral double-stranded DNA (dsDNA) levels, although AR1 and AL2 mutants accumulate only small amounts of single-stranded viral DNA (ssDNA). In contrast, a large reduction in both ss- and dsDNA levels is observed when a mutation is introduced into ORF AL3. Mutations within either of the two DNA B ORFs do not affect DNA replication. The AL3, BR1, and BL1 mutants are capable of synthesizing coat protein; however, coat protein is not detected in leaf discs inoculated with AR1 or AL2 mutants. Testable models are proposed to explain the influence of AL2 protein on coat protein accumulation and to account for the stimulation of viral DNA synthesis mediated by the AL3 gene product.
番茄金黄花叶病毒（TGMV）是一种双生病毒，其基因组分为两个DNA组分，分别命名为A和B。TGMV基因组包含六个开放阅读框（ORF），这些开放阅读框能够编码分子量大于10 kDa的蛋白质。我们利用原生质体转染系统来确定由这些开放阅读框所定义的病毒蛋白对受感染细胞中病毒DNA积累的影响。同时也在叶圆片中检测了外壳蛋白的积累情况。我们的结果表明，开放阅读框AR1和AL2中的突变并不影响病毒双链DNA（dsDNA）水平，尽管AR1和AL2突变体仅积累少量的单链病毒DNA（ssDNA）。相比之下，当在开放阅读框AL3中引入突变时，单链和双链DNA水平均大幅降低。两个DNA B开放阅读框中任何一个的突变都不影响DNA复制。AL3、BR1和BL1突变体能够合成外壳蛋白；然而，在用AR1或AL2突变体接种的叶圆片中未检测到外壳蛋白。我们提出了可验证的模型来解释AL2蛋白对外壳蛋白积累的影响，并说明由AL3基因产物介导的病毒DNA合成的刺激作用。
