Complementation of Virus Movement in Transgenic Tobacco Expressing the Cucumber Mosaic Virus 3a Gene

• Published in: Virology (New York, N.Y.) N.Y.), 1995-05, Vol.209 (1), p.188-199
• Main Authors: Kaplan, Igor B., Shintaku, Michael H., Li, Qiubo, Zhang, Lee, Marsh, Loren E., Palukaitis, Peter
• Format: Article
• Language: English
• Subjects: cucumber mosaic virus; Cucumovirus - genetics; Cucumovirus - metabolism; Cucumovirus - pathogenicity; CUCUMOVIRUS DEL MOSAICO DEL PEPINO; CUCUMOVIRUS MOSAIQUE DU CONCOMBRE; Defective Viruses - genetics; EXPRESION GENICA; EXPRESSION DES GENES; GENE; Gene Expression; GENES; Genes, Viral; Genetic Complementation Test; GENETICA; GENETIQUE; MOUVEMENT; MOVIMIENTO; Mutation; Nicotiana - virology; NICOTIANA TABACUM; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; Plants, Genetically Modified; Plants, Toxic; PROTEINAS; PROTEINE; RNA, Viral - genetics; RNA, Viral - metabolism; Viral Proteins - genetics; VIRUS DE LAS PLANTAS; VIRUS DES VEGETAUX
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1006/viro.1995.1242

Tobacco plants were transformed with the cucumber mosaic cucumovirus (CMV) 3a gene and the in planta-expressed 3a protein was detected immunologically. The 3a protein was predominantly localized in a subcellular fraction corresponding to the cytosol. Two frameshift and four deletion mutants were created within the 3a open reading frame of CMV RNA 3. Five of these mutants, containing an N-terminal, large central, or C-terminal 70-amino-acid deletion could not infect nontransformed tobacco plants, but could infect the 3a transgenic tobacco plants, and generally accumulated to wild-type levels. The sixth mutant, lacking the C-terminal 43 amino acids of the 3a protein, was able to infect nontransformed tobacco plants. A delay in accumulation of viral RNA in both the inoculated and the systemically infected leaves was demonstrated for one of the mutants. Thus, the CMV 3a protein is a virus movement protein, the functions of which can be complemented in a transgenic plant. The CMV 3a transgenic plants were able to complement the long-distance movement of a pseudorecombinant cucumovirus defective for this function in tobacco, as well as the cell-to-cell, but not the long-distance, movement of two other related viruses. However, these transgenic plants were unable to complement the long-distance movement of viruses from several other taxonomic groups that could move cell to cell but not long distance in tobacco.