Effects of Mutagenesis in vitro on the Ability of Cloned Tomato Golden Mosaic Virus DNA to Infect Nicotiana benthamiana Plants

Abstract

Insertion mutations introduced in vitro into cloned DNA of tomato golden mosaic virus that considerably shortened the length of the open reading frames (ORFs) AL1, AL2/AL3, BL1 or BR1, abolished the ability of the DNA to infect Nicotiana benthamiana seedlings. Mutants in which ORF AR1 was similarly shortened by an insertion or a 28 bp deletion were infections, showing that the formation of coat protein or virions is not reqired for replication and systemic spread of virus DNA, although the appearance of symptoms was delayed in infections with the deletion mutant. Mutants with larger deletions (178 bp to 603 bp) in ORF AR1 were not infectious. Infections could be initiated with mixtures of AL1 and AL2/AL3 mutants, or BL1 and BR1 mutants, primarily as a result of complementation, although a low proportion of wild-type DNA A molecules regenerated by recombination or reversion was detected in the progeny of infection with the DNA A mutants.