|Meng, Baozhong - UNIV OF GUELPH|
Submitted to: Research Trends
Publication Type: Review Article
Publication Acceptance Date: May 3, 2003
Publication Date: June 3, 2003
Citation: Meng, B., Gonsalves, D. 2003. Rupestris stem pitting associated virus: genome organization, heterogeneity, rapid detection, and relationships with other plant viruses. Research Trends. Current Topics in Virology. 3:125-135. Research Trends. Interpretive Summary: Rupestris stem pitting is a widespread viral disease of grapevines that is manifested primarily in the cultivar 'St. George'. Up until the lat five years, little information on the causal agent was known due to the difficulty in purifying the virus particles from grapevines. Breakthroughs in cloning and sequencing the double stranded RNA found in infected plants enabled the researchers to obtain the complete genome sequence of the virus, Rupestris stem pitting associated virus (RSPaV) that is associated with the disease. Thus, antibodies have been produced to the coat protein, rapid detection methods by polymerase chain reaction technology have been developed, and recently, antiserum to coat protein have been used to visualize the virus particles by electron microscopy. This review article gives details on these discoveries and suggests areas of future research.
Technical Abstract: As a component of the most important Rugose wood disease complex, Rupestris stem pitting (RSP) is the most prevalent viral disease of grapevines worldwide. Two major problems are associated with RSP. First, little was known regarding the biological aspects of the causative agent of the disease. Second, diagnosis of RSP is achieved through biological indexing on indicator Vitis Rupestris 'St. George', a tedious procedure that takes two or three years to complete. By taking a new and alternative approach, much advancement has been made on the putative causal virus of RSP in the past decade. A high molecular weight double-stranded RNA was first shown to be associated with RSP. The dsRNA was cloned and sequenced, which revealed a viral genome that is similar in structure to potexviruses, carlaviruses, and allexiviruses. The virus was designated Rupestris stem pitting associated virus (RSPaV) or Grapevine Rupestris stem pitting associated virus. Several lines of evidence clearly indicate that RSPaV, as a viral species, is not a homogeneous entity but is composed of a family of distinct sequence variants that differ extensively in genome sequence. It was also clearly shown that grapevines, at least scion varieties, are often infected with more multiple sequence variants. Based on the information of genome sequence, reverse transcription-polymerase chain reaction assays were first established for the rapid detection of RSPaV. The detection efficiency varies largely depending on the primers used. The coat protein of RSPaV was expressed in bacterial cells and polyclconal antibodies were produced against the recombinant proteins. Serological methods such as Western blot and indirect enzyme-linked immunosorbent assays have been developed. These nucleic acid- and protein-based diagnostic methods are advantageous as compared to the classical indicator indexing, because they are much quicker, as reliable, more sensitive, and more suitable for large-scale assays. More recently, viral particles of RSPaV were identified, for the first time, with immunosorbent electron microscopy using the antiserum. In addition, clear evidence indicates that the 'St. George' plants used as the indicators are infected with an apparent latent strain of RSPaV, the genome of which has recently been sequenced. The possible phylogenetic relationship of RSPaV with viruses from several other viral groups is discussed. The authors also provide their point of view for future research directions.