Cucumber mosaic virus D satellite RNA-induced programmed cell death in tomato

D satellite RNA (satRNA) with its helper virus, namely, cucumber mosaic vir us, causes systemic necrosis in tomato. The infected plant exhibits a disti nct spatial and temporal cell death pattern. The distinct features of chrom atin condensation and nuclear DNA fragmentation indicate that programmed ce ll death is involved. In addition, satRNA localization and terminal deoxynu cleotidyltransferase-mediated dUTP nick end labeling show that cell death i s initiated from the infected phloem or cambium cells and spreads to other nearby infected cells. Timing of the onset of necrosis after inoculation im plicates the involvement of cell developmental processes in initiating toma to cell death. Analysis of the accumulation of minus- and plus-strand satRN As in the infected plants indicates a correlation between high amounts of m inus-strand satRNA and tomato cell death.