Analysis for effct of the ratios of CMV RNA species on the viral multiplicalion in tobacco tissues

分析了抑制黄瓜花叶病毒(CMV)增殖的机理，特别是花叶绿岛组织和无症状叶片周期性出现在感染CMV的烟草上。烟草履历表Xanthi北卡罗来纳州感染了CMV-PEPO无卫星分离物，并对感染的早期阶段进行了分析。无症状叶片和绿色组织对接种病毒颗粒或病毒RNA的CMV具有抗性，这些组织含有CMV基因组的双链RNA3和4。它们含有极低水平的CMV单链RNA，其侵染性和外壳蛋白(CP)含量仅为黄色组织的5%。从各叶位组织中回收的病毒颗粒中，RNA3和RNA4与RNA1和RNA2的体积之比因每片叶上出现的症状类型而异。无症状叶片出现在叶片上方，RNA3和RNA4与RNA1和RNA2的比值较大。绿岛病毒的增殖受到严重抑制，但在绿岛组织制备的原生质体中病毒增殖得到恢复。根据这些结果，无症状叶片或绿色组织中的抗性不被认为是由CP引起的。CMV RNA的复制可能被某种未知的机制特异性地抑制。较大体积的RNA3和RNA4可导致形成无症状的叶片或绿岛。

Mechanism for the suppression of cucumber mosaic virus (CMV) multiplication is analyzed, with special reference to the green island tissue of mosaic leaves and the symptomless leaves periodically appear in the CMV-infected tobacco plants. Tobacco cv. Xanthi nc. was infected with a satellite-free isolate of CMV-pepo and analyzed for the early stage of infection. The symptomless leaves and the green tissue were resistant to the CMV inoculation with virus particles or viral RNA.Those tissues contained double stranded RNA 3 and 4 of the CMV genome. They contained very low level of single stranded RNA of CMV.They contained infectivity and coat protein (CP) as low as 5% of those in the yellow tissue. Ratios for the volume of RNA 3 and 4 to RNA 1 and 2 in the virus particles recovered from the tissues on each leaf position varied along with the symptom types appeared on each leaves. Symptomless leaves appeared above the leaves with larger ratio of RNA 3 and 4 to RNA 1 and 2. Virus multiplication was severely suppressed in the green islands, however, it was recovered in the protoplasts prepared from the green tissue. From these results, resistance in the symptomless leaves or the green tissue is not considered to be caused by CP.Replication of CMV RNA might be specifically suppressed by some unknown mechanism. Larger volume of RNA 3 and 4 may cause to develop the symptomless leaves or the green islands.