Lunello Pablo, Mansilla Carmen, Sánchez Flora, Ponz Fernando
Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Madrid, Spain.
Mol Plant Microbe Interact. 2007 Dec;20(12):1589-95. doi: 10.1094/MPMI-20-12-1589.
Possible effects of host developmental stage on the amount of virus present in systemically infected plant tissues hitherto have received little attention. In this study, the pattern of virus accumulation over the plant lifespan has been examined in systemically invaded tissues of Arabidopsis thaliana infected by either of two distinct (+)RNA viruses: Turnip mosaic virus, a member of Potyvirus, and Oilseed rape mosaic virus, a member of Tobamovirus. Quantitative analyses of virus coat protein and virus genomic RNA in roots versus aerial plant parts revealed generally sinusoidal temporal patterns of virus accumulation. In noninoculated leaves, a time period was found during which no virus accumulation was detected. This period was coincident with the approximately 7 days of inflorescence bud formation and differentiation. In roots, virion content reached high levels a few days after inoculation, dropping dramatically during the period of bud formation and quickly recovering after it. These results, together with electron microscopy observations, are consistent with loss of virions due to disassembly. Fluorescence observations of green fluorescent protein-tagged virus-infected root tissue also were consistent with a net loss of virus-specified proteins. Inoculations performed after the emergence of the inflorescence and on A. thaliana flowering-time mutants support the temporal link between observed changes in virus content and inflorescence bud formation. Different host-involving biochemical processes can be invoked to provide mechanistic clues, but no one of them alone seems sufficient to explain the complex patterns of tight temporal regulation of virus accumulation observed in these experiments.
宿主发育阶段对系统感染植物组织中病毒含量的可能影响，迄今为止很少受到关注。在本研究中，已在被两种不同的（+）RNA病毒之一感染的拟南芥系统侵染组织中，研究了病毒在植物整个生命周期中的积累模式：芜菁花叶病毒，一种马铃薯Y病毒属成员；以及油菜花叶病毒，一种烟草花叶病毒属成员。对根与地上植物部分中的病毒外壳蛋白和病毒基因组RNA进行定量分析，揭示了病毒积累通常呈正弦时间模式。在未接种的叶片中，发现了一个未检测到病毒积累的时间段。这个时间段与大约7天的花序芽形成和分化期一致。在根中，病毒粒子含量在接种后几天达到高水平，在芽形成期急剧下降，并在芽形成期之后迅速恢复。这些结果，连同电子显微镜观察结果，与病毒粒子因解体而损失一致。对绿色荧光蛋白标记的病毒感染根组织的荧光观察结果也与病毒特异性蛋白的净损失一致。在花序出现后对拟南芥开花时间突变体进行接种，支持了观察到的病毒含量变化与花序芽形成之间的时间联系。可以调用不同的涉及宿主的生化过程来提供机制线索，但其中任何一个单独看来都不足以解释在这些实验中观察到的病毒积累的复杂紧密时间调控模式。
