Isotation and analysis of symptom expression genes in virus-infected by transposon-tagging method.

为探讨黄瓜花叶病毒（CMV[Y]）侵染烟草（Nicotiana tabacum' ky57 '）叶片严重绿斑病症状的遗传决定因素，比较了N。用巨细胞病毒(Y)、巨细胞病毒(O)或两种巨细胞病毒的假重组体接种的烟草（ky57）、烟草（xanthi nc）及其杂交品种。苍耳c在CMV(Y)接种的叶片中表现出非常轻微的黄斑症状。CMV(O)接种的Ky57和苍耳nc叶片均未出现症状。在假重组接种的Ky57叶片中，通过嵌合CMV(O)和CMV(Y)RNA3转录本确定了严重症状，这些转录本包含了CMV(Y)的大部分外壳蛋白基因。巨细胞病毒(Y)重症症状形成的遗传分析。假重组接种的烟草表明，两个隐性核编码宿主基因决定了CMV(Y)接种的Ky57的严重症状形成。两个隐性寄主遗传位点与Ky57的两个隐性白肋基因（yb1和yb2基因）完全共分离，其特征是茎部叶绿素含量明显降低。将不同品种的白肋烟接种CMV(Y)后，所有白肋烟均明显表现出严重的症状，而其他品种则表现出非常轻微的症状。这些结果表明，接种CMV(Y)的Ky57的严重黄斑症状的形成是由病毒外壳蛋白基因和与yb基因密切相关或相同的两个隐性宿主基因联合诱导的。

To investigate the genetic determinants of severe chlorotic spot symptoms in cucumber mosaic virus(CMV[Y])-inoculated tobacco(Nicotiana tabacum'Ky57')leaves, symptom expression was compared among tobaccos(N.tabacum'Ky57', N.tabacum'Xanthi nc', and their hybrids)inoculated with CMV(Y), CMV(O), or pseudorecombinants of both strains of CMV.Xanthi nc showed very mild chlorotic spot shmptoms in CMV(Y)-inoculated leaves. Both CMV(O)-inoculated Ky57 and Xanthi nc leaves showed no symptoms. In pseudorecombinant-inoculated Ky57 leaves, severe symptoms were determined by chimeric CMV(O)and CMV(Y)RNA3 transcripts, which contained most of the coat protein gene of CMV(Y). Genetic analysis of severe sympotom formation in CMV(Y). or pseudorecombinantinoculated tobaccos indicated that two recessive nuclearcoded host genes determined severe symptom formation in CMV(Y)-inoculated Ky57. The two recessive host genetic loci completely cosegregated with the two recessive burley loci(yb1 and yb2 genes)of Ky57, whose character is an apparent reduction in chlorophyll of the stems. When several cultivars of N.tabacum were inoculated with CMV(Y), all burley tobaccos clearly showed severe symptoms, but most other cultivars showed very mild symptoms, These results suggest that severe chlorotic spot symptom formation in CMV(Y)-inoculated Ky57 is induced by a combination of the virus coat protein gene and two recessive host genes that are closely linked to or identical to yb genes.