Recombinant constructions and infectivity analysis of tobacco mosaic virus and attenuated tomato mosaic virus N14 genomes

Abstract

The recombinant clones of pTN and pNT have been constructed by exchanging the coding regions of the movement proteins (MP), coat proteins (CP) and 3− noncoding regions between the cDNAs of the tobacco mosaic virus (Chinese Isolate, TMV-Cv) and the attenuated tomato mosaic virus N14 genomes, and used as templates forin vitro runoff transcription. Their transcripts have been used for tobacco infection assays. The infection results show that the transcripts of pTN and pNT are infectious. Local lesions were observed in the leaves ofNicotiana tabacum cv. Samsun NN inoculated with pTN transcript, but were fewer than those in the same kind of plant induced by pTMV-Cv transcript. Systemic symptoms were also observed inN. tabacum cv. Huangmiaoyu induced by pTN transcript, but were slighter than those on the same kind of tobacco induced by pTMV-Cv transcript. Local lesions were shown inN. tabacum cv. Samsun NN inoculated with pNT transcript, but were more than those in the same kind of plant induced by pN14 transcript while no systemic symptom was displayed inN. tabacum cv. Huangmiaoyu. These results suggest that the recombinant viruses of TN and NT are able to propagate in the assayed tobaccos, and they keep the most same phenotypic character with pTMV-Cv and pN14 transcripts, and TMV-Cv and N14 as well. The conjunctions between the replicase and the MP, CP and 3− noncoding regions are not stringent. Apparently there is a compatible function complementation between the homologous subgenomes of TMV-Cv and N14. From those above it could be probably presumed that the mutagenized replicase gene of N14 plays a major role In contributing to the virus attenuation while its mutagenized MP gene could avianize the symptoms of the infected tobaccos.