Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2015
Publication Date: 6/26/2015
Publication URL: http://handle.nal.usda.gov/10113/61033
Citation: Edwards, M.C., Weiland, J.J., Todd, J., Stewart, L.R. 2015. Infectious Maize rayado fino virus from cloned cDNA. Phytopathology. 105:833-839.
Interpretive Summary: Maize rayado fino virus (MRFV) is the type member of a group of plant-infecting viruses known as marafiviruses. These viruses are of interest because of their inability to infect all tissues of a plant host, as well as their ability to replicate in both plant and insect hosts. Techniques for producing and inoculating recombinant viral genomes would open new avenues for investigation of these viruses and further our general knowledge of virus-vector interactions. In this study, a clone of a US isolate of MRFV was produced that induces typical symptoms of MRFV infection in maize plants (stunting and chlorotic stipple striping of leaves), as well as the accumulation of viral products characteristic of native MRFV infection. Furthermore, the cloned virus was transmissible by both the corn leafhopper and the black-faced leafhopper. This constitutes the first report of a full-length MRFV clone from which infectious RNA can be generated, providing the foundation for future discoveries regarding the ability of some viruses to infect both plants and insects, the ability of some viruses to be transmitted by leafhoppers, and the inability of some viruses to move outside the vascular tissues of infected plants.
Technical Abstract: Maize rayado fino virus (MRFV) is the type member of the marafiviruses within the family Tymoviridae. A cDNA clone from which infectious RNA can be transcribed was produced from a US isolate of MRFV (MRFV-US). Infectivity of transcripts derived from cDNA clones was demonstrated by infection of maize plants and protoplasts, as well as by transmission via the known leafhopper vectors Dalbulus maidis and Graminella nigrifrons that transmit the virus in a persistent-propagative manner. Infection of maize plants through vascular puncture inoculation of seed with transcript RNA resulted in the induction of fine stipple stripe symptoms typical of those produced by wild type MRFV and a frequency of infection comparable to that of wild type. Northern and western blotting confirmed the production of MRFV-specific RNAs and proteins in infected plants and protoplasts. An unanticipated increase in sgRNA synthesis over levels in infected plants was observed in protoplasts infected with either wild-type or cloned virus. Sequence analysis revealed a conserved motif previously identified in both OBDV capsid protein and tymoviral non-structural protein processing near the amino terminus of the replicase polyprotein, suggesting cleavage at this site also may occur.