RESISTANCE TO TOBAMOVIRUSES IN TRANSGENIC TOBACCO PLANTS EXPRESSING THE COAT PROTEIN GENE OF PEPPER MILD MOTTLE VIRUS (KOREAN ISOLATE)

Red pepper, one of the most important vegetable crops in Korea, is sev erely affected by viral diseases causing 20-50% reduction in product y ield, A pepper strain of tobacco mosaic virus (TMV-p) is the most comm on virus in red pepper, To study the molecular structure of the TMV-p virus, we generated cDNA clones of the viral genome, Partial sequencin g of a few cDNA clones revealed that TMV-p shares a 98% identity at th e nucleotide level with the Spanish isolate of pepper mild mottle viru s (PMMV-s), This suggests that TMV-p should be reclassified as the Kor ean isolate of PMMV (PMMV-k). The coat protein (CP) gene together with the 3' untranslated region of the PMMV-k virus was obtained by revers e transcriptase-polymerase chain reaction (RT-PCR) using oligomers ded uced from the sequence of PMMV-s, The sequence analysis of the CP gene and the 3' untranslated region further confirmed that PMMV-k is highl y related to PMMV-s. The CP gene and the 3' untranslated region of PMM V-k were cloned into a plant expression vector and the construct was i ntroduced into tobacco plants, The transgenic plants expressing the PM MV-k CP gene were delayed in developing systemic disease or failed to develop symptoms at all after inoculation with PMMV-k. Delay of sympto ms was also observed when the plants were inoculated with TMV-OM which shares a 74% homology with PMMV-k in the amino acid sequence of the C P region, In a local lesion host, the CP expressing plants exhibited a greatly reduced number of necrotic lesions as compared to control pla nts after inoculation with TMV-OM, Our results show that CP-mediated v iral resistance is readily applicable in the case of PMMV-k and can pr ovide resistance to other viruses in the tobamovirus group.