ASSOCIATION OF BAMBOO MOSAIC-VIRUS (BOMV) AND BOMV-SPECIFIC ELECTRON-DENSE CRYSTALLINE BODIES WITH CHLOROPLASTS

Infection of green bamboo (Bambusa oldhamii) with bamboo mosaic virus (BoMV), a possible member of the potexvirus group, is associated with the formation of a large number of unusual electron-dense crystalline bodies (EDCBs) and virion aggregates in the infected cells. The infection sequence was studied using leaf tissues prepared for electron microscopy. At an early stage of infection, before BoMV virion formation, EDCBs that lacked clear internal structure were detected in the chloroplasts and were used as infection initiation markers. At a later stage, BoMV virions were observed to be attached to the chloroplasts, whereas EDCBs containing ribosomelike beads occurred free and abundantly in the cytoplasm. In cells at a late stage of infection, masses of BOMV virions were readily observed in the cytoplasm and vacuoles. However, the EDCBs were restricted to the cytoplasm and nuclei. Only the EDCBs observed in the cytoplasm were closely associated with the BoMV virions. Immunogold labeling showed that the localization of capsid protein during infection corresponded with the localization of virions by ordinary electron microscopy, except that immunogold-labeled virions or BoMV antigens also were labeled along the plasma membrane during the early stage of infection. No virions or viral antigen were detected in other organelles. The EDCBs were not labeled using the antiserum to BoMV capsid protein, indicating that EDCBs do not contain BoMV antigenic determinants identical to those of BoMV virions.