Phytopathology. 2002 Jun;92(6):646-53. doi: 10.1094/PHYTO.2002.92.6.646.
ABSTRACT The inner lining of the food canal of nematodes that transmit plantinfecting viruses is regarded as the retention region of viruses. To characterize the location of transmissible and nontransmissible viruses in the vector nematode Xiphinema americanum, three nepoviruses, Tobacco ringspot virus (TRSV), Tomato ringspot virus(TomRSV), and Cherry leaf roll virus(CLRV), and one non-nematode-transmissible virus, Squash mosaic virus (SqMV), were evaluated for transmission efficiency and localization sites in the nematode. Transmission trials showed highest transmission efficiency for TomRSV (38% with 1 and 100% with 10 nematodes, respectively), intermediate efficiency for TRSV (27% with 1 and 65% with 10 nematodes, respectively), and no transmission for CLRV and SqMV. Electron microscopy and immunofluorescent labeling revealed that TRSV was primarily localized to the lining of the lumen of the stylet extension and the anterior esophagus, but only rarely in the triradiate lumen. Within a nematode population, particles of TRSV were no longer observed in these three regions 10 weeks after acquisition, and it is assumed that there was gradual and random loss of the virus from these areas. The percentage of nematodes that were labeled by virus-specific immunofluorescent labeling in a population of viruliferous nematodes decreased gradually after TRSV acquisition when the nematodes were placed on a nonhost of the virus, and the loss of immunofluorescent labeling paralleled the decrease in the ability of the nematode population to transmit the virus. TomRSV was localized only in the triradiate lumen based on thin-section electron microscopy. No virus-like particles were observed in any part of the food canal of nematodes that had fed on CLRV-infected plants. Virus-like particles that appeared to be partially degraded were observed only in the triradiate lumen of nematodes that had fed on SqMV-infected plants. These results clarified the status of localization of two nontransmissible viruses in X. americanum and presented evidence that two nematode-transmissible viruses, TRSV and TomRSV, are localized in different regions of the food canal of X. americanum.
摘要 植物病毒介体线虫的食物道内层被认为是病毒的保留区。为了确定可传播和不可传播病毒在传播线虫 Xiphinema americanum 中的定位，我们评估了三种线状病毒，烟草环斑病毒（TRSV）、番茄环斑病毒（TomRSV）和樱桃叶卷病毒（CLRV），以及一种非介体线虫可传播病毒，南瓜花叶病毒（SqMV），在线虫中的传播效率和定位部位。传代试验表明，TomRSV 的传播效率最高（分别用 1 条和 10 条线虫获得 38%和 100%的传代效率），TRSV 的传播效率居中（分别用 1 条和 10 条线虫获得 27%和 65%的传代效率），而 CLRV 和 SqMV 则没有传播。电子显微镜和免疫荧光标记显示，TRSV 主要定位于口针延伸和前食道的内腔衬里，但在三叉内腔中很少见。在获得线虫后 10 周，线虫种群中不再观察到 TRSV 颗粒，并且假设病毒逐渐且随机地从这些区域丢失。在获得 TRSV 后，当线虫被放置在非病毒宿主上时，用病毒特异性免疫荧光标记标记的线虫在种群中的比例逐渐降低，并且免疫荧光标记的丢失与线虫种群传播病毒的能力降低平行。TomRSV 仅通过薄切片电子显微镜定位于三叉内腔。从感染 CLRV 的植物中取食的线虫的食物道的任何部位都没有观察到病毒样颗粒。仅从感染 SqMV 的植物中取食的线虫的三叉内腔中观察到似乎部分降解的病毒样颗粒。这些结果阐明了两种非传染性病毒在 X. americanum 中的定位状态，并提供了证据表明两种线虫可传播病毒，TRSV 和 TomRSV，定位于 X. americanum 食物道的不同区域。
