Localization of Genetic Information Involved in the Replication of Alfalfa Mosaic Virus

Abstract

Cowpea protoplasts were inoculated with different combinations of the 4 nucleoprotein components of alfalfa mosaic virus (AlMV) and the synthesis of viral particles, coat protein and RNA was analyzed. Synthesis of viral particles and coat protein was detectable by polyacrylamide gel electrophoresis only when the inoculum contained the components bottom [B], middle [M] and top b [Tb], accomodating RNA 1, 2 and 3, respectively. Upon inoculation with B + M + Tb, the synthesis of viral RNA was detectable by annealing of radiolabeled RNA frm protoplasts to virus-specific double-stranded RNA. On inoculation with B + Tb or M+ Tb, no significant amount of viral RNA was produced. After inoculation with B + M, the production of virus-specific RNA was about 40% of that induced by complete infection, indicating that genetic information encoded by RNA 1 and 2 is involved in viral RNA replication. Since a mixture of the genomic RNA did not induce synthesis of virus-specific RNA, coat protein is evidently required for RNA synthesis induced by the mixture of B and M nucleoproteins. Since no coat protein is produced upon inoculation with B + M + Ta components, the replicase activity induced by B + M evidently does not replicate RNA 4, the messenger for coat protein present in Ta particles.