Complementation and recombination between mutants of complementary sense genes of DNA A of Abutilon mosaic virus.

Mutations have been inserted into the complementary sense ORFs of DNA A of Abutilon mosaic virus (AbMV). Mutation in both ORF AC1 and ORF AC2/3 resulted in clones incapable of infecting Nicotiana benthamiana following agroinoculation. Mutation in ORF AC1 but not in ORF AC2/3 prevented DNA replication in leaf discs. Thus ORF AC1 is essential for AbMV DNA replication whereas ORF AC2/3 is probably involved in some aspect of the spread of the virus through the plant. Coagroinoculation of both mutants and wild-type DNA B resulted in complementation and recombination. Complementation precedes recombination and once recombination is established mutant DNA can no longer be detected. Plants in which complementation alone is occurring are symptomless and contain relatively low amounts of virus double-stranded DNA whereas following recombination a wild-type infection is established.