Kavanagh T, Goulden M, Santa Cruz S, Chapman S, Barker I, Baulcombe D
Department of Genetics, Trinity College, Dublin, Ireland.
Virology. 1992 Aug;189(2):609-17. doi: 10.1016/0042-6822(92)90584-c.
Full-length cDNA clones of potato virus X (PVX) strains PVXUK3 and PVXHB have been constructed in plasmid vectors to allow in vitro transcription of infectious PVX RNA. In both instances the transcript-derived virus infected tobacco and potato identically to the respective progenitor strains: in tobacco and susceptible potato cultivars both strains infected systemically, producing symptomless or mild mosaic symptoms. In potato carrying the Rx or Nx resistance genes, the virus derived from the PVXHB cDNA infected systemically, whereas the virus derived from the PVXUK3 cDNA failed to infect the Rx plants or induced apical necrosis, characteristic of a hypersensitive response of the Nx gene. Three hybrid viral genomes were constructed at the cDNA level to localize the resistance breaking determinants of PVXHB. Transcripts of all three hybrids were infectious on tobacco. On potato cultivars with either the Rx or Nx resistance genes, the hybrid viruses infected in the same way as PVXHB, rather than PVXUK3. The common feature of these hybrid viruses, the coat protein gene, is therefore the determinant of Nx and Rx resistance breaking of PVXHB.
已将马铃薯X病毒（PVX）毒株PVXUK3和PVXHB的全长cDNA克隆构建到质粒载体中，以实现感染性PVX RNA的体外转录。在这两种情况下，转录本衍生病毒对烟草和马铃薯的感染情况与各自的亲本毒株完全相同：在烟草和易感马铃薯品种中，两种毒株均能系统感染，产生无症状或轻度花叶症状。在携带Rx或Nx抗性基因的马铃薯中，源自PVXHB cDNA的病毒能系统感染，而源自PVXUK3 cDNA的病毒无法感染Rx植株或诱导顶端坏死，这是Nx基因超敏反应的特征。构建了三个杂交病毒基因组，以在cDNA水平上定位PVXHB的抗性突破决定因素。所有三个杂交体的转录本在烟草上均具有感染性。在具有Rx或Nx抗性基因的马铃薯品种上，杂交病毒的感染方式与PVXHB相同，而非PVXUK3。因此，这些杂交病毒的共同特征——外壳蛋白基因，是PVXHB打破Nx和Rx抗性的决定因素。
