The 3a Protein from Cucumber Mosaic Virus Increases the Gating Capacity of Plasmodesmata in Transgenic Tobacco Plants Vaquero, C. and Turner, A. P. and Demangeat, G. and Sanz, A. and Serra, M. T. and Roberts, K. and García-Luque, I.,, 75, 3193-3197 (1994), doi = https://doi.org/10.1099/0022-1317-75-11-3193, publicationName = Microbiology Society, issn = 0022-1317, abstract= The 3a protein, encoded by RNA 3 of cucumber mosaic virus (CMV), is the putative movement protein of viral progeny in infected plants. An analysis of transgenic tobacco plants constitutively expressing the CMV 3a protein showed that the protein is accumulated in leaves at every stage of development. In fully expanded leaves the protein is immunodetectable mostly in a cell-wall- enriched fraction. Dye-coupling experiments using fluor- escent-dextran probes were performed on fully expanded leaves to study the modifying effect of CMV 3a protein on the gating capacity of plasmodesmata. Movement of fluorescein-isothiocyanate-labelled dex- tran with a mean molecular mass of 10000 Da, and an approximate Stokes’ radius of 2·3 nm, was detected between cells of the 3a protein transgenic plants, but not in the control plants. These results are consistent with the idea that the CMV 3 a protein is involved in the modification of plasmodesmata and, therefore, in the cell-to-cell spread of the virus., language=, type=