Brome mosaic virus replicase proteins localize with the movement protein at infection-specific cytoplasmic inclusions in infected barley leaf cells

Subcellular localization of the Brome mosaic virus replicase-related 1a and 2a proteins, and the 3a movement protein in infected barley leaves was exa mined by immunogold electron microscopy. The la and 2a proteins colocalized at infection-specific electron-dense cytoplasmic inclusions. The 3a protei n was also detected in these inclusions. The inclusions were oval or amorph ous, and contained electron-lucent regions. Electron microscopic autoradiog raphy showed that the inclusions were sites of [H-3]uridine incorporation, suggesting that they are sites of viral RNA synthesis.