Characterization of a Brassica-infecting comovirus from Ohio

A turnip plant grown in a University of Toledo greenhouse showed unusual symptoms that we thought were due to a virus. Initial symptoms on turnips are chlorotic lesions on systemic leaves. Older leaves show chlorotic ringspot symptoms and line patterns along veins while younger leaves show chlorotic lesions. To examine the breadth of the host range for the putative virus, different plant species were inoculated. TuRSV (Turnip ringspot virus ) was able to induce symptoms mainly on plants of the Brassicaceae but not in other families.; The virus induces systemic symptoms on Arabidopsis thaliana, a member of the Brassica family. TuRSV was inoculated onto twenty-four A. thaliana ecotypes to obtain additional information on its host range.{09}A variety of symptomatology was observed, from death to no obvious symptoms on the plants. The virus caused a lethal infection in the Ct-1 ecotype. Some ecotypes, such as Aa-0, show an unusual relationship with the virus. Aa-0 recovered from the initial symptoms and flowered, although the recovery process was complicated. Such a recovery mechanism is the first reported case for this phenomenon against a virus in Arabidopsis.; Col-0 plants were mostly resistant to the virus. The fact that the Col-0 ecotype is resistant permitted a detailed study of virus-host interactions. Col-0 mutants defective in the ethylene, jasmonic acid, salicylic acid signaling pathways exhibited no symptoms, similar to Col-0 wild type plants suggesting Col-0 resistance may not use classical signaling pathways.; F1 and F2 data suggests that Col-0 resistance may be due to a single recessive gene, but only in Oy-0 background. The symptoms for the F2s derived from crosses of either Nw-4, Aa-0 with Col-0 are far more complicated. Leaf dip electron microscopy and other data suggested that the pathogen is not present at high titer. Electron microscopy performed on the infectious sucrose gradient fractions detected icosahedral virus particles 26-28 nanometers in diameter. A pan-comovirus RT-PCR assays performed on virus infected samples showed positive results, indicating that TuRSV is a comovirus. Taken together these data suggest that TuRSV is a new member of the comovirus family.