De Jong W, Chu A, Ahlquist P
Institute for Molecular Virology, University of Wisconsin-Madison 53706-1596, USA.
Virology. 1995 Dec 20;214(2):464-74. doi: 10.1006/viro.1995.0057.
The M1 and M2 strains of brome mosaic virus (BMV) both systemically infect the monocot host barley, but only the M2 strain systemically infects the dicot cowpea line TVu-612. We have shown previously that this difference in host range maps primarily to RNA3. To further characterize the role of RNA3 in host specificity, a series of RNA3 hybrids were tested, in inoculations with M1 RNA1 and RNA2, for ability to systemically infect TVu-612 cowpea. Although all hybrids were amplified well in cowpea protoplasts and all supported systemic infection in barley plants, only those with the 3a cell-to-cell movement gene of BMV-M2 supported systemic infection of cowpea. The sequences of the M1 and M2 3a proteins differ at four positions. Introducing these four coding differences individually or in various combinations into M1 RNA3 revealed that all four influenced BMV adaptation to cowpea and that these four differences were sufficient to account for the difference in ability between M1 and M2 RNA3s to support systemic infection of this legume. These coding changes were also associated with faster spread of infection in inoculated cowpea leaves, suggesting that they influence the ability to systemically infect TVu-612 cowpea through effects on the rate of cell-to-cell spread.
雀麦花叶病毒（BMV）的M1和M2株系均可系统感染单子叶宿主大麦，但只有M2株系能系统感染双子叶豇豆品系TVu - 612。我们之前已经表明，宿主范围的这种差异主要映射到RNA3上。为了进一步表征RNA3在宿主特异性中的作用，我们测试了一系列RNA3杂种，在接种M1 RNA1和RNA2时，检测其系统感染TVu - 612豇豆的能力。尽管所有杂种在豇豆原生质体中均能良好扩增，并且在大麦植株中均支持系统感染，但只有那些具有BMV - M2的3a细胞间移动基因的杂种支持豇豆的系统感染。M1和M2 3a蛋白的序列在四个位置存在差异。将这四个编码差异单独或以各种组合引入M1 RNA3，结果表明所有四个差异均影响BMV对豇豆的适应性，并且这四个差异足以解释M1和M2 RNA3在支持该豆科植物系统感染能力上的差异。这些编码变化还与接种的豇豆叶片中感染的更快传播相关，表明它们通过影响细胞间传播速率来影响系统感染TVu - 612豇豆的能力。
