In vivo encapsidation of potato spindle tuber viroid by velvet tobacco mottle virus particles.

When Nicotiana clevelandii was inoculated simultaneously with velvet tobacco mottle virus (VTMoV) and potato spindle tuber viroid (PSTV), replication of the viroid was greatly suppressed. However, both pathogens replicated if PSTV was inoculated several days before the VTMoV. Small amounts of PSTV were detected by dot-blot analysis of RNA in highly purified VTMoV isolated from coinfected plants indicating that the viroid had been encapsidated by the virus particles. Moreover, tomato plants which are immune to VTMoV became infected with PSTV when inoculated with VTMoV containing the viroid. Implications of these results are discussed in relation to questions regarding the spread and evolution of viroids and viroid-like satellite RNAs.