Silencing Suppressor P19 Research Articles

A chemically inducible cucumber mosaic virus amplicon system for expression of heterologous proteins in plant tissues

A novel cucumber mosaic virus inducible viral amplicon (CMViva) expression system has been developed that allows for tightly regulated chemically inducible expression of heterologous genes in plant hosts. Transient production of recombinant alpha(1)-antitrypsin (rAAT), a human blood protein, was demonstrated in Nicotiana benthamiana leaves. The highest production levels were obtained by co-infiltrating leaves with Agrobacterium tumefaciens cells containing CMViva carrying the AAT gene and A. tumefaciens cells carrying a binary vector constitutively expressing the gene silencing suppressor p19. Accumulation of up to thirty-fold more rAAT was observed in leaves (24 mg per 100 g leaf tissue) when compared with the expression levels observed using the cauliflower mosaic virus (CaMV) 35S promoter. Significantly, 70% of the rAAT produced using the CMViva expression system was found to be biologically active, a 170-fold increase in functional protein compared with the CaMV 35S expression system.

Occurrence of artichoke mottle crinkle virus in leaf vein xylem

Traditional virus inoculation of plants involves mechanical rubbing of leaves, whereas in nature viruses like Tomato bushy stunt virus (TBSV) are often infected via the roots. A method was adapted to compare leaf versus root inoculation of Nicotiana benthamiana and tomato with transcripts of wild-type TBSV (wtTBSV), a capsid (Tcp) replacement construct expressing GFP (T-GFP), or mutants not expressing the silencing suppressor P19 (TBSVΔp19). In leaves, T-GFP remained restricted to the cells immediately adjacent to the site of inoculation, unless Tcp was expressed in trans from a Potato virus X vector; while T-GFP inoculation of roots gave green fluorescence in upper tissues in the absence of Tcp. Conversely, leaf inoculation with wtTBSV or TBSVΔp19 transcripts initiated systemic infections, while upon root inoculation this only occurred with wtTBSV, not with TBSVΔp19. Evidently the contribution of Tcp or P19 in establishing systemic infections depends on the point-of-entry of TBSV in the plants.