Flow cytometric analysis of tobacco and cowpea protoplasts infected in vivo and in vitro with alfalfa mosaic virus.

Immunofluorescence flow cytometry was used to study the distribution of viral antigen in protoplast populations. Protoplasts were isolated from healthy and alfalfa mosaic virus (AMV) infected tobacco leaves (designated in vivo infected). Furthermore isolated tobacco and cowpea protoplasts were infected in vitro with AMV. The FITC-conjugated antibodies could penetrate formaldehyde fixed protoplasts. The flow cytometric measurements were rapid and reproducible. Comparable immunofluorescence patterns were found for all infected samples (per sample 10(4) protoplasts were measured). Infectious virus could only be detected in in vivo infected tobacco protoplasts and in in vitro infected cowpea protoplasts.