Klein P G, Klein R R, Rodríguez-Cerezo E, Hunt A G, Shaw J G
Department of Horticulture and Landscape Architecture, University of Kentucky, Lexington 40546.
Virology. 1994 Nov 1;204(2):759-69. doi: 10.1006/viro.1994.1591.
We have used a cDNA clone of the potyvirus, tobacco vein mottling virus, to construct 19 mutants bearing 12-nt insertions in the viral genome. These mutants display a variety of phenotypes in inoculated tobacco plants or protoplasts. All mutants with insertions in P3, CI, 6K, NIa, or NIb failed to produce detectable amounts of progeny viral RNA in protoplasts or plants which suggests that they all may be directly involved in replication. Mutants (one in P1 and one in HCpro) presumably affected in polyprotein processing also did not replicate in plants or protoplasts. Seven mutants, with insertions in the 5' noncoding region, P1, HCpro, or CP regions of the genome, were able to infect protoplasts. Three of the 7 mutants (1 in the 5' noncoding region and 2 in HCpro) were able to infect protoplasts but not plants. The remaining 4 mutants replicated in protoplasts and were able to cause systemic infection in plants. The mutation in the CP had no effect on virus accumulation or symptom development in inoculated plants, whereas the other 3 (1 in P1 and 2 in HCpro) induced cyclical patterns of symptom expression. These symptoms ranged from very mild to wild-type-like as new leaves emerged and, as the plants continued to grow, this pattern was repeated. These results support the assignment of roles in replication to five coding regions in the genome and demonstrate that sequence alterations in many parts of other regions of the viral genome may have pronounced effects on replication and the expression of disease symptoms.
我们利用马铃薯Y病毒属的烟草脉斑驳病毒的一个cDNA克隆构建了19个在病毒基因组中带有12个核苷酸插入片段的突变体。这些突变体在接种的烟草植株或原生质体中呈现出多种表型。所有在P3、CI、6K、NIa或NIb中插入的突变体在原生质体或植株中均未能产生可检测到的子代病毒RNA，这表明它们可能都直接参与复制。推测在多聚蛋白加工过程中受到影响的突变体（一个在P1，一个在HCpro）在植株或原生质体中也不能复制。7个在基因组的5'非编码区、P1、HCpro或CP区插入的突变体能够感染原生质体。这7个突变体中的3个（1个在5'非编码区，2个在HCpro）能够感染原生质体但不能感染植株。其余4个突变体在原生质体中复制，并能够在植株中引起系统感染。CP中的突变对接种植株中的病毒积累或症状发展没有影响，而其他3个（1个在P1，2个在HCpro）诱导出周期性的症状表达模式。随着新叶长出，这些症状从非常轻微到类似野生型，并且随着植株继续生长，这种模式会重复出现。这些结果支持了基因组中五个编码区在复制中所起作用的分配，并表明病毒基因组其他区域许多部分的序列改变可能对复制和病害症状表达有显著影响。
