Biology and structure of plant satellite viruses activated by icosahedral helper viruses.

Abstract

Nearly 40 years ago, Kassanis and Nixon (1960) described two kinds of particles in tobacco necrosis virus (TNV) infections that differed in size, and thus seemed to be separate viruses. The smaller component was demonstrated to depend on the larger autonomous virus for its multiplication, and hence was designated a satellite virus, satellite tobacco necrosis virus (STNV). This discovery quickly stimulated research in several areas of biology and chemistry with a focus on relationships, pathology, transmission, and interdependence of STNV and TNV. Following the realization of the satellite nature of STNV, identification of other satellite viruses was remarkably slow compared with the rates of discovery of new viruses, satellite RNAs, and viroids. More than 15 years passed before a second satellite virus, satellite panicum mosaic virus (SPMV; Fig. 1), was described (Buzen et al. 1984; Niblett and Paulsen 1975). A satellite virus particle associated with maize white line mosaic virus (MWLMV) that constitutes a third distinct satellite virus was subsequently identified (Gingery and Louie 1985; Zhang et al. 1991a). The helper viruses that support replication of these three satellite viruses are all isometric and have monopartite genomes. However, particle morphology of the helper virus seems to be inconsequential for support of isometric satellite viruses, since a fourth satellite virus, satellite tobacco mosaic virus (STMV), naturally occurs in Nicotiana glauca infected with the rod-shaped tobacco mosaic virus (Valverde and Dodds 1986).KeywordsMosaic VirusCapsid ProteinNecrosis VirusHelper VirusTohacco Necrosis VirusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.