Replicase-Mediated Resistance to Cucumber Mosaic Virus in Transgenic Plants Involves Suppression of Both Virus Replication in the Inoculated Leaves and Long-Distance Movement

• Published in: Virology (New York, N.Y.) Vol. 199; no. 2; pp. 439 - 447
• Main Authors: Carr, John P., Gal-On, Amit, Palukaitis, Peter, Zaitlin, Milton
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.03.1994; Elsevier
• Subjects: Agronomy. Soil science and plant productions; Base Sequence; Biological and medical sciences; CHLOROSE; CLOROSIS; cucumber mosaic virus; Cucumovirus - immunology; Cucumovirus - physiology; CUCUMOVIRUS DEL MOSAICO DEL PEPINO; CUCUMOVIRUS MOSAIQUE DU CONCOMBRE; Fundamental and applied biological sciences. Psychology; GENETICA; GENETIQUE; Microbiology; Molecular Sequence Data; Nicotiana - microbiology; NICOTIANA TABACUM; Plants, Genetically Modified - immunology; Plants, Genetically Modified - microbiology; Plants, Toxic; Protoplasts - immunology; Protoplasts - microbiology; Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains; RESISTANCE AUX MALADIES; RESISTENCIA A LA ENFERMEDAD; RNA, Viral - analysis; RNA-Dependent RNA Polymerase - physiology; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; Virion; Virology; Virus Replication - immunology; Plant pathogen; Enzyme; Transferases; Mechanism; RNA-directed RNA polymerase; Virus; Nucleotidyltransferases; Microorganism resistance; Dissemination; Cucumber mosaic virus; Replication; Cucumovirus; Transgenic plant; Inhibition
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1006/viro.1994.1142

Tobacco plants transformed with a gene encoding a truncated cucumber mosaic virus (CMV) 2a replicase protein are resistant to systemic CMV disease. Experiments using protoplasts derived from plants of two R 2-generation CMV-resistant transgenic plant lines (lines R 2-2 and R 2-5) showed that resistance operates at the single cell level. Low levels of CMV-specific RNAs were detected in CMV-inoculated protoplasts obtained from both R 2-2 and R 2-5 plants indicating that resistance is due at least in large part to a marked but incomplete suppression of virus replication. Leaves of immature plants belonging to line R 2-2 occasionally exhibited local chlorosis when inoculated with high concentrations of CMV. Areas of local chlorosis were sites of low but detectable levels of CMV RNA, CMV virions, and CMV replicase activity, but did not act as foci for subsequent systemic disease. An antiserum raised against the CMV 2a replicase protein overexpressed in Escherichia coli was used to detect the presence of trace amounts of the truncated CMV 2a replicase protein in CMV-resistant transgenic tobacco plants. It was concluded that expression of the transgene, potentially as protein, engenders resistance primarily by suppressing virus replication but may also, to a lesser extent, do so by inhibiting systemic movement of the virus.