Molecular Genetic Analysis of Host Specificity in Plant Viruses

大多数植物病毒在多种植物的直接接种细胞中复制，但在启动细胞间传播和/或随后在植物中维持系统传播方面表现出精细的宿主特异性。作为分子研究植物病毒基因在运动、全身感染和宿主特异性中的个体和集体作用的基础，研究人员已经制作并鉴定了几种不同宿主范围和基因组序列差异的不同溴病毒的完整的感染性cDNA克隆。并证明了在这些病毒之间设计交换选定的基因和基因片段为鉴定宿主特异性决定因素和表征其行为提供了强有力的方法。基于这些工具和溴病毒分子生物学的强大一般特征，他们现在将：在细胞水平上跟踪感染运动，以确定不同病毒基因改变时全身感染被阻断的不同阶段；将宿主特异性效应映射到几个相关病毒基因的特定功能域，并测试基于自然RNA重组的RNA病毒遗传作图的潜在强大新方法；试验初步表明，与“门控”假说相反，成功的全身感染需要3a运动基因与1a和2a复制基因之间的相互适应；确定1a和2a基因在复制后对全身性感染的明显影响是否真正独立于它们在RNA复制中的已知功能；并在3a基因周围的非编码序列中定位观察到的宿主特异性决定因素，并确定它们对3a基因表达的可能影响。研究结果应该为植物对感染病毒的反应提供澄清的概念。

Most plant viruses replicate in directly inoculated cells from a wide range of plants, but show exquisite host specificity with respect to initiating cell-to-cell and/or sustaining subsequent systemic spread through the plant. As a foundation for molecular study of the individual and collective role of plant virus genes in movement, systemic infection, and host specificity, the investigators have produced and characterized complete, infectious cDNA clones of several distinct bromoviruses of varying divergence in host range and genome sequence, and demonstrated that designed exchange of selected genes and gene segments between such viruses provides a powerful approach for identifying host specificity determinants and characterizing their behavior. Building on these tools and the strong general characterization of bromovirus molecular biology, they will now: follow infection movement at the cellular level to define the distinct stages at which systemic infection is blocked upon alteration of different virus genes; map host specificity effects to specific functional domains of several implicated virus genes and test a potentially powerful new approach to RNA virus genetic mapping based on natural RNA recombination; test preliminary indications that, contrary to the "gating " hypothesis, successful systemic infection requires mutual adaptation between the 3a movement gene and the 1a and 2a replication genes; determine whether the apparently post-replication influence of the 1a and 2a genes on systemic infection is truly independent of their known functions in RNA replication; and localize observed host specificity determinants in noncoding sequences surrounding the 3a gene and determine their possible influence on 3a gene expression. The results should provide clarifying concepts regarding the plant's response to the infective viruses.