Infectivity of heterologous RNA-protein mixtures from alfalfa mosaic, citrus leaf rugose, citrus variegation, and tobacco streak viruses

Abstract

RNA preparations of alfalfa mosaic virus (AMV), citrus leaf rugose virus (CLRV), and citrus variegation virus (CVV) were separated into two size-classes by successive cycles of sucrose density gradient centrifugation. One class contained the three heaviest RNA's: CVV-RNA 1 + 2 + 3, CLRV-RNA 1 + 2 + 3, and AMV-RNA 1 + 2 + 3. The other contained the lightest or two lightest RNA's: CVV-RNA 4 + 4a, CLRV-RNA 4, and AMV-RNA 4. Protein was isolated from preparations of AMV, CLRV, CVV, tobacco streak virus (TSV), brome mosaic virus (BMV), and cowpea chlorotic mottle virus (CCMV) by dialysis against CaCl 2. Infectivity assays showed that noninfectious mixtures of the three heaviest RNA's of AMV, CLRV, or CVV could each be activated by addition of protein from AMV, CLRV, CVV, and TSV. These RNA mixtures could also be activated by the lightest RNA's of CVV, CLRV, and AMV. Symptoms of infected plants always resembled that of the virus supplying the three heaviest RNA's regardless of the activating protein or RNA. Proteins isolated from BMV and CCMV failed to activate any of the RNA mixtures. Serological relationships were not observed between AMV and TSV and the citrus viruses (CLRV, CVV). The serological relationship between CLRV and CVV was confirmed.