Abstract
The distribution of potyviruses in mixed infected Nicotiana benthamiana plants was investigated by using green and red fluorescent proteins (GFP, DsRed). Full-length cDNA clones of Plum pox virus (PPV-NAT-AgfpS; PPV-NAT-red), Tobacco vein mottling virus (TVMV-gfp; TVMV-red) and Clover yellow vein virus (ClYVV-GFP) expressing fluorescent proteins, referred to here as labelled viruses, were used to characterize the distribution of different potyviral populations (e.g. TVMV-gfp/PPV-NAT-red), as well as populations of identical, but differently labelled potyviruses (e.g. PPV-NAT-AgfpS/PPV-NAT-red) or in mixed infections of potyviruses with labelled Potato virus X (PVX). Plants infected by any of the PVX/potyvirus combinations exhibited synergistic symptoms and large numbers of cells were doubly infected. In contrast, co-infections of differently labelled potyvirus populations appeared non-synergistic and remained predominantly separate in the infected plants, independent of whether different viruses or identical but differently labelled viruses were co-infecting. Contact of differently labelled virus populations that exhibited spatial separation was restricted to a small number of cells at the border of different fluorescent cell clusters.