title: Widely separated sequence elements within cucumber mosaic virus satellites contribute to their ability to induce lethal tomato necrosis.
abstract: To determine the structural requirements for cucumber mosaic virus (CMV) satellites to elicit lethal tomato necrosis, three satellite variants D, S and Y were used in the construction and cloning of chimeric cDNAs. D and S are necrogenic and non-necrogenic 'prototype' variants, respectively, and Y possesses the 3' conserved necrosis-determining region but does not cause lethal tomato necrosis. Its 5' half harbours an insertion/deletion region that results in a molecule about 30 nucleotides longer than other variants. Tomato bio-assays were conducted with RNA transcripts of all six chimeric combinations of the 5' and 3' halves of the three satellite variants divided by a common restriction site, as well as with a mutated chimera. None of the chimeras containing the 5' half of Y induced lethal necrosis in tomato even when their 3' halves were that of the D variant with the conserved necrogenic element. Chimeras with the 3' half of Y elicited only partial or restricted necrosis which was much less severe than that induced by prototype variant D, and often was not lethal. Site-directed mutation of a single nucleotide in proximity to the necrogenic element of such a chimera containing the 3' half of Y restored much lethal necrogenicity. The results revealed the presence of structural elements in CMV satellite variant Y that modulate or even suppress the expression of the 3' conserved necrosis-determining element. They indicate that in CMV satellites widely separated sequence elements constituting a three-dimensional requirement are responsible for eliciting lethal necrosis in tomato.
mesh_terms: D001483:Base Sequence; D001681:Biological Assay; D017124:Conserved Sequence; D004252:DNA Mutational Analysis; D004274:DNA, Recombinant / Q000235:genetics; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009029:Mosaic Viruses / Q000235:genetics* / Q000472:pathogenicity; D009336:Necrosis; D010935:Plant Diseases / Q000382:microbiology*; D010944:Plants / Q000382:microbiology*; D012313:RNA / Q000235:genetics*; D019244:RNA, Satellite; D012367:RNA, Viral / Q000235:genetics*; D014774:Virulence
chemical_list: D004274:DNA, Recombinant; D019244:RNA, Satellite; D012367:RNA, Viral; D012313:RNA