THE MOVEMENT PROTEIN AND COAT PROTEIN OF ALFALFA MOSAIC-VIRUS ACCUMULATE IN STRUCTURALLY MODIFIED PLASMODESMATA

In systemically infected tissues of Nicotiana benthamiana, alfalfa mos aic virus (AMV) coat protein (CP) and movement protein (MP) are detect ed in plasmodesmata in a layer of three to four cells at the progressi ng front of infection. Besides the presence of these viral proteins, t he plasmodesmata are structurally modified in that the desmotubule is absent and the diameter has increased drastically (almost twofold) whe n compared to plasmodesmata in uninfected cells or cells in which AMV infection had been fully established. Previously reported observations on virion-containing tubule formation at the surface of AMV-infected protoplasts suggest that AMV employs a tubule-guided mechanism for int ercellular movement. Although CP and MP localization to plasmodesmata is consistent with such a mechanism, no tubules were found in plasmode smata of AMV-infected tissues. The significance of these observations is discussed. (C) 1998 academic Press.