Appl Environ Microbiol. 1995 Nov;61(11):3950-9. doi: 10.1128/aem.61.11.3950-3959.1995.
Spiroplasmavirus SVTS2, isolated from Spiroplasma melliferum TS2, produces plaques when inoculated onto lawns of Spiroplasma citri M200H, a derivative of the type strain Maroc R8A2. S. citri strains MR2 and MR3, originally selected as colonies growing within plaques on a lawn of M200H inoculated with SVTS2, were resistant to SVTS2. Genomic DNA fingerprints and electrophoretic protein profiles of M200H, MR2, and MR3 were similar, but three proteins present in M200H were missing or significantly reduced in both resistant lines. None of these three polypeptides reacted with antiserum against S. citri membrane proteins, indicating that they probably are not surface-located virus receptors. Electroporation with SVTS2 DNA produced 1.5 x 10(sup5) transfectants per (mu)g of DNA in M200H but none in MR2 or MR3, suggesting that resistance may result from inhibition of viral replication. The digestion patterns of the extrachromosomal double-stranded (ds) DNA of these lines were similar. Three TaqI fragments of MR2 extrachromosomal DNA that were not present in M200H extrachromosomal DNA hybridized strongly to an SVTS2 probe, and two of these fragments plus an additional one hybridized with the MR3 extrachromosomal DNA, indicating that a fragment of SVTS2 DNA was present in the extrachromosomal ds DNA of MR2 and MR3 but not of M200H. When the restricted genomes of all three lines were probed with SVTS2 DNA, strong hybridization to two EcoRI fragments of chromosomal MR2 and MR3 DNA but not M200H DNA indicated that SVTS2 DNA had integrated into the genomes of MR2 and MR3 but not of M200H. When MR3 extrachromosomal ds DNA containing a 2.1-kb SVTS2 DNA fragment was transfected into M200H, the transformed spiroplasmas were resistant to SVTS2. These results suggest that SVTS2 DNA fragments, possibly integrated into the chromosomal or extrachromosomal DNA of a previously susceptible spiroplasma, may function as viral incompatibility elements, providing resistance to superinfection by SVTS2.
从蜜蜂蜜蜂螺旋体 TS2 中分离到的螺旋体病毒 SVTS2，在接种到柑橘螺旋体 M200H 草坪上时会产生斑块，M200H 是 Maroc R8A2 型菌株的衍生物。最初选择作为在接种 SVTS2 的 M200H 草坪上的斑块内生长的菌落的柑橘螺旋体菌株 MR2 和 MR3 对 SVTS2 具有抗性。M200H、MR2 和 MR3 的基因组 DNA 指纹图谱和电泳蛋白图谱相似，但 M200H 中存在的三种蛋白质在两条抗性线中缺失或明显减少。这三种多肽都没有与柑橘螺旋体膜蛋白的抗血清发生反应，表明它们可能不是位于表面的病毒受体。用 SVTS2 DNA 电穿孔在 M200H 中产生了每微克 DNA 1.5 x 10(sup5)的转染子，但在 MR2 或 MR3 中都没有，这表明抗性可能是由于病毒复制的抑制。这些线的染色体外双链 (ds) DNA 的消化模式相似。MR2 染色体外 DNA 中不存在的三个 TaqI 片段与 SVTS2 探针强烈杂交，其中两个片段加上另一个片段与 MR3 染色体外 DNA 杂交，表明 SVTS2 DNA 的一个片段存在于 MR2 和 MR3 的染色体外 ds DNA 中，但不存在于 M200H 中。当用 SVTS2 DNA 探测这三种线的受限基因组时，强烈杂交到 MR2 和 MR3 染色体 DNA 的两个 EcoRI 片段，但没有与 M200H DNA 杂交，表明 SVTS2 DNA 已整合到 MR2 和 MR3 的基因组中，但不是 M200H 的基因组。当含有 2.1kb SVTS2 DNA 片段的 MR3 染色体外 ds DNA 被转染到 M200H 中时，转化的螺旋体对 SVTS2 具有抗性。这些结果表明，SVTS2 DNA 片段，可能整合到先前易感螺旋体的染色体或染色体外 DNA 中，可能作为病毒不相容元件发挥作用，提供对 SVTS2 超感染的抗性。
