Malcuit I, de Jong W, Baulcombe D C, Shields D C, Kavanagh T A
Department of Genetics, Trinity College, Dublin 2, Ireland.
Virus Genes. 2000;20(2):165-72. doi: 10.1023/a:1008178800366.
Resistance to potato virus X (PVX) is determined by the product of a host resistance gene and a viral determinant specifying either virulence (resistance-breaking ability) or avirulence (resistance sensitivity). The viral coat protein is the determinant of resistance mediated by the host Nx gene while the 25 kDa movement protein is the determinant of Nb-mediated resistance. Group 1 and group 4 strains of PVX are avirulent or virulent respectively for both these determinants while group 2 and group 3 strains are virulent for one but avirulent for the other determinant. There are two alternative evolutionary mechanisms by which the various strain groups might have evolved: either by recombination between strains carrying virulence (or avirulence) determinants that evolved once only, or alternatively, by independent evolution of at least one virulence (or avirulence) determinant in distinct phylogenetic branches. These alternative hypotheses were investigated by (i) determining the complete genomic sequence of a group 1 and a group 4 strain and (ii) comparing the completely sequenced genomes of six isolates representative of the four strain groups. The analysis revealed the same phylogeny for all five PVX genes. Thus, there is no evidence that the PVX strain groups evolved by recombination.
对马铃薯X病毒（PVX）的抗性由宿主抗性基因的产物和一个病毒决定因子决定，该病毒决定因子决定毒力（抗性破坏能力）或无毒力（抗性敏感性）。病毒外壳蛋白是由宿主Nx基因介导的抗性决定因子，而25 kDa运动蛋白是Nb介导的抗性决定因子。PVX的第1组和第4组菌株对这两个决定因子分别无毒或有毒，而第2组和第3组菌株对其中一个决定因子有毒，但对另一个决定因子无毒。有两种可供选择的进化机制，各种菌株组可能通过这些机制进化：要么是携带仅进化一次的毒力（或无毒力）决定因子的菌株之间发生重组，要么是至少一个毒力（或无毒力）决定因子在不同的系统发育分支中独立进化。通过（i）确定第1组和第4组菌株的完整基因组序列，以及（ii）比较代表四个菌株组的六个分离株的完全测序基因组，对这些替代假设进行了研究。分析揭示了所有五个PVX基因相同的系统发育。因此，没有证据表明PVX菌株组是通过重组进化而来的。
