Tabler M, Sänger H L
EMBO J. 1984 Dec 20;3(13):3055-62. doi: 10.1002/j.1460-2075.1984.tb02257.x.
A set of monomeric and oligomeric potato spindle tuber viroid (PSTV) specific DNA forms representing complete DNA copies of the circular PSTV RNA genome were constructed and cloned in plasmid pBR322 and bacteriophage M13. Both single- and double-stranded PSTV DNAs are capable of initiating viroid replication in mechanically inoculated tomato plants where it normally proceeds via the RNA-RNA pathway without DNA being involved. All dimeric and higher multimeric forms were infectious irrespective of their polarity in the case of single-stranded DNA and regardless of their orientation in the vector DNA in the case of double-stranded DNA. The vector-inserted monomeric PSTV DNA units were also found to be infectious but of low specific infectivity which was increased when these monomers had been excised. Even two subgenomic DNA fragments, representing together the 359 nucleotides of the PSTV RNA genome, initiated the synthesis of viroid RNA progeny when co-inoculated although each fragment by itself is non-infectious. These results are discussed with respect to the infectivity previously observed with certain cloned DNAs of conventional RNA and DNA viruses.
构建了一组代表环状马铃薯纺锤块茎类病毒（PSTV）RNA基因组完整DNA拷贝的单体和寡聚体PSTV特异性DNA形式，并将其克隆到质粒pBR322和噬菌体M13中。单链和双链PSTV DNA都能够在机械接种的番茄植株中启动类病毒复制，在番茄植株中，类病毒复制通常通过RNA-RNA途径进行，不涉及DNA。所有二聚体和更高阶的多聚体形式都具有感染性，单链DNA的情况下与它们的极性无关，双链DNA的情况下与它们在载体DNA中的方向无关。还发现载体插入的单体PSTV DNA单元具有感染性，但特异性感染性较低，当这些单体被切除时，感染性会增加。即使是两个亚基因组DNA片段，合起来代表PSTV RNA基因组的359个核苷酸，共同接种时也能启动类病毒RNA子代的合成，尽管每个片段本身没有感染性。结合先前用传统RNA和DNA病毒的某些克隆DNA观察到的感染性对这些结果进行了讨论。
