Characterization of an infectious clone of pepper ringspot virus and its use as a viral vector.

The genus Tobravirus comprises three species: Tobacco rattle virus, Pea early-browning virus and Pepper ringspot virus. The genomes of tobraviruses consist of two positive-sense single-stranded RNA segments (RNA1 and RNA2). Infectious clones of TRV are extensively used as virus-induced gene-silencing (VIGS) vectors for studies of virus-host interactions and functions of plant genes. Complete infectious clones of pepper ringspot virus (PepRSV), the only tobravirus present in Brazil, however, have not yet been reported. Infectious clones will help to identify unique features of PepRSV RNA2 and provide another option for development of VIGS vectors. We constructed infectious clones based on two PepRSV isolates, CAM (RNA1 and RNA2) and LAV (RNA2). The cDNA constructs for both homologous (RNA1 and RNA2 of the CAM isolate) and heterologous (RNA1/CAM and RNA2/LAV) combinations were infectious in Nicotiana benthamiana plants. VIGS vector constructs with green fluorescent protein or phytoene desaturase genes inserted in RNA2 silenced the target genes. The systemic translocation of the PepRSV RNA1 construct alone (nonmultiple infection) was also confirmed in an N. benthamiana plant. These results are similar to those reported for tobacco rattle virus.