Infectious eggplant mosaic tymovirus and ononis yellow mosaic tymovirus from cloned cDNA.

Eggplant mosaic virus (EMV) and ononis yellow mosaic virus (OYMV) are two tymoviruses that have ssRNA genomes of about 6.2 kb and 6.3 kb, and which infect solanaceous and leguminous hosts, respectively. Full-length cDNA clones of these viruses were constructed with a T7 promoter adjacent to the 5' terminus of the DNA copy of the viral genome, and with unique restriction endonuclease sites at the 3' terminus. This allowed RNA to be transcribed from the DNA encoding the genome. The transcript RNA was infectious when inoculated to Nicotiana glutinosa (for EMV) and Pisum sativum (for OYMV). These clones, together with clones of turnip yellow mosaic tymovirus, which infects brassicas, have been used to construct hybrids in which the virion protein gene was exchanged between EMV or OYMV and turnip yellow mosaic virus. These and other hybrids are being used to investigate the molecular basis for host range differences in tymoviruses.