SENSE AND ANTISENSE COAT PROTEIN GENE CONSTRUCTS CONFER HIGH-LEVELS OF RESISTANCE TO TOMATO RINGSPOT NEPOVIRUS IN TRANSGENIC NICOTIANA SPECIES

The coat protein (cp) gene and the 3' end untranslated region of a pea ch isolate of tomato ringspot virus (TomRSV) were cloned from purified total viral RNA and sequenced. Reverse transcription and polymerase c hain reaction (RT-PCR) were used to engineer the TomRSV cp gene so tha t it could be cloned into plasmid vectors designed for either in vitro transcription or plant expression. The cloned TomRSV cp gene was used to transform Nicotiana benthamiana and N. tabacum plants, a systemic and a local lesion host, respectively. After challenge inoculation wit h the TomRSV peach isolate, several R(0), R(1), and R(2) resistant tra nsgenic lines containing sense and antisense cp constructs exhibited d ifferent levels of protection ranging from complete resistance to dela y in symptom appearance or reduction in symptom severity. Interestingl y, cp gene expression levels were undetectable by enzyme-linked immuno sorbent assay (ELISA) in the resistant lines containing cp sense const ructs, and levels of cp transcripts were low or undetectable by Northe rn blot on resistant sense and antisense lines. The high level of resi stance obtained in Nicotiana spp. offers important prospects for the e ngineering of TomRSV resistance into several economically important fr uit and berry crops susceptible to this nepovirus.