PSEUDORECOMBINATION AND COMPLEMENTATION BETWEEN POTATO YELLOW MOSAIC GEMINIVIRUS AND TOMATO GOLDEN MOSAIC GEMINIVIRUS

Pseudorecombinants made by exchanging the cloned, infectious genome co mponents (DNAs A and B) of potato yellow mosaic geminivirus (PYMV) and the common strain (cs) of tomato golden mosaic geminivirus (csTGMV) a re not infectious in their common host Nicotiana benthamiana. In an N. benthamiana leaf disc assay neither PYMV DNA A nor TGMV DNA A trans-r eplicated each other's DNA B component. The ability of PYMV and TGMV t o mediate the systemic movement of each other's DNA A was investigated following coinoculation of N. benthamiana with both genome components of one virus (the helper virus) and DNA A of the other virus (the dep endent virus). Movement of the dependent virus DNA A in both cases ill ustrates interchangeability between the DNA B-encoded movement protein s of New World geminiviruses which infect solanaceous hosts. We have s tudied this genetic interchangeability further in separate co-agroinoc ulation experiments with N. benthamiana plants using TGMV DNA A to com plement mutations in PYMV open reading frame (ORF) AC2, which encodes a protein that trans-activates the expression of virion sense promoter s, and in PYMV ORF AC3, which specifies a protein that enhances viral DNA replication. TGMV DNA A complemented a PYMV AC2 mutant and restore d its infectivity and it also complemented a PYMV AC3 mutant and resto red the reduced DNA phenotype.