The coat protein of satellite panicum mosaic virus (SPMV) was used to stabilize viral vector gene inserts in planta. A Potato virus X (PVX) vector carrying the SPMV capsid protein (CP) gene was successfully stabilized through three serial passages in Nicotiana benthamiana from the upper non-inoculated leaves following rub inoculation. The presence of SPMV CP expression from the PVX vector was confirmed by necrotic lesions that occur only when SPMV CP is present and by western blot and reversetranscription PCR analyses. In addition, PVX-SPCP was co-inoculated onto N. benthamiana with a Tomato bushy stunt virus vector carrying a green fluorescent protein gene, which normally does not yield GFP expression in upper tissue due to loss of the insert. However, upon co-inoculation with PVX-SPCP, upper non-inoculated leaves exhibited GFP accumulation based on green fluorescence by UV illumination at 488 nm and western blot analysis. GFP expression was more abundant in upper non-inoculated N. benthamiana leaves as well as systemic tissues when the co-inoculation experiments were performed at 20°C compared to 25°C. These results suggest that SPMV CP is a viable molecular tool for stabilizing viral vector gene inserts in planta.