Analysis of local and systemic spread of the crucifer-infecting TMV-Cg virus in tobacco and several Arabidopsis thaliana ecotypes

The crucifer-infecting tobacco mosaic virus, TMV-Cg, infects Arabidopsis thaliana ( L.) Heynh. efficiently without causing severe symptoms. The systemic spread of TMV-Cg in Arabidopsis was evaluated in 14 ecotypes. Five days after inoculation, TMV-Cg was detected in apical leaves of 8 out of 14 ecotypes. As expected, the spread of TMV-Cg in the ecotypes tested was considerably faster than that of tobacco mosaic virus (TMV-U-1). To study the participation of viral proteins in the TMV-Cg-induced infection, a complete genomic cDNA of TMV-Cg was cloned. The role of TMV-Cg movement protein in systemic spread was tested with a hybrid virus, constructed from the TMV-U1 genome and the TMV-Cg movement protein gene. Contrary to expectations, the systemic spread of this hybrid in Arabidopsis was similar to that of TMV-U1. The failure of the hybrid virus to spread at rates similar to those of TMV-Cg was not due to restrictions in local movement. In tobacco ( Nicotiana tabacum L.), the hybrid virus spread efficiently and induced systemic mosaic symptoms characteristic of TMV-U1. The TMV-Cg cDNA clone provides an attractive tool to study virus-host interactions.