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Tomato Cell Death Mediated By Complementary Plant Viral Satellite RNA Sequences

Cell death (necrosis) and severe yellowing (chlorosis) in tomato are induced by cucumber mosaic virus (CMV) supporting particular satellite RNAs. To determine whether CMV RNA sequences also are needed to induce necrosis or chlorosis, tomato seedlings were infected with the potato virus X vector expressing either a necrogenic or chlorosis-inducing satellite RNA of CMV. The infected plants did not develop chlorosis, although they did develop necrosis, but only when all or part of a 335-nucleotide necrogenic satellite RNA was expressed in the (-) polarity; i.e., the strand not packaged in virus particles. Computer-assisted secondary structure analysis suggests that the necrogenicity domain is an octanucleotide loop and adjacent base-paired stem of a thermodynamically stable hairpin structure.