Figure 4

Immmunogold label of virus infected P. betae zoospores. (A, B) Arrows point to gold particles detecting viral replicase. Note in a, the arrows are in a row pointing to gold particles in the cytoplasm, vesicles, and extracellular space. This could represent the path of virus movement between the zoospore and zoosporangial sac detailed in the model in Fig 1c. Vesicles are irregularly shaped. Some are horseshoe shaped, others are surrounding pockets of cytoplasm, and some are reaching outside of the zoospore body. (C, D) shows zoospore and vesicles treated with coat protein antiserum. Vesicles contain fibers of unknown origin. (E, F) Zoospores treated with P14 and P31 antiserum, respectively. Both label the zoospore vacuoles/vesicles and zoosporangial wall. (G, H) shows BNYVV virions (arrowheads) in plant cells, along the plant cell wall. Gold particle in both panels label coat protein or virions. Virions were not found inside zoosporangium or sporosorus. (I) shows zoosporangial wall (zw) near plant cell wall (cw) and plasmodesmata. ZW seems to block plasmodesmata. Gold particles label P31 proteins. There are unknown projections through plasmodesmata. Edge of zoospore shows vesicles extending into the zoosporangial milieu. Bars represent 1 μm.