Fate of African Cassava Mosaic Virus Coat Protein Deletion Mutants after Agroinoculation

SUMMARY We have investigated the behaviour of coat protein deletion mutants of the geminivirus African cassava mosaic virus (ACMV) when introduced into Nicotiana benthamiana by agroinoculation. In dividing callus tissue, replicating mutant DNA A, in the absence of DNA B, remained subgenomic in size. However, systemic infection of plants was associated with the rapid reversion of the deletion mutants to native component size, as happened when the mutants were introduced into the host by more conventional mechanical inoculation procedures. The results contrast with those reported for tomato golden mosaic virus (TGMV) for which similar mutants, agroinoculated into N. benthamiana, remained subgenomic. The results indicate that the inoculation route is not responsible for the different behaviour of ACMV and TGMV mutants and illustrate a significant difference between the interaction of these otherwise closely related geminiviruses with a common host that might be exploited for the investigation of the determinants of DNA replication and spread.