An infectious full-length cDNA clone of Chrysanthemum virus B (CVB, genus Carlavirus), was constructed. Four cDNA fragments covering the whole genome of CVB-S were cloned between the Cauliflower mosaic virus 35S promoter and the nopaline synthase (NOS) terminator. Chrysanthemum and garland chrysanthemum were inoculated with the constructed plasmid, named pCVB, using a gene gun system. As is the case in wild-type, CVB-infected plants, no visible symptoms were observed on plants inoculated with pCVB; however, western blotting and electron microscopy indicated the presence of the progeny virus of pCVB. pCVB could be a useful tool for analyzing the functions of carlaviral proteins.

Turnip mosaic virus (TuMV) is a member of the genusPotyvirus and is the only potyvirus known to cause devastating diseases of cruciferous plants. TuMV is a filamentous virion containing a positive-sense, single-stranded RNA that is covalently attached at the 5 0 -end to a viral protein linked to the genome (VPg) and polyadenylated at the 3 0 -end. This study is divided into two main areas. One involves the molecular biological analysis of viral factors relevant to TuMV infectivity and pathogenicity. The other describes the development of a rapid and simplified method for reverse transcription polymerase chain reaction (RT-PCR) for detecting viruses possessing distinctly shaped particles.Host range determinant between cabbage (Brassica oleracea L.) and Japanese radish (Raphanus sativus L.)A Japanese isolate of TuMV, TuC, causes systemic chlorotic spots in infected cabbage but does not systemically infect radish. However, TuR1 systemically infects both plants, with a mild chlorotic mottle in cabbage and mosaic symptoms in radish. Inoculation with many chimeric clones through the exchange of cDNA fragments between the two viruses revealed that the P3 gene was important in the determination of their host range. Analysis by tissue immunoblotting of inoculated leaves showed that the P3 gene played a role in both virus accumulation and longdistance movement. Symptom determinant in Arabidopsis thalianaTuC and TuR1 are capable of efficient systemic infection in many ecotypes of A. thaliana, with severe symptoms. However, in the case of infection of ecotype Landsberg erecta (Ler), TuC caused mosaic symptoms, whereas TuR1 induced systemic veinal necrosis. Using a number of chimeric viruses, the N-terminal region of P3 was mapped as responsible for the characteristic symptomatology on Ler. Binding analyses of the interaction between the VPg and eukaryotic initiation factor (eIF) 4E isoform [eIF(iso)4E]Binding of the eIF4E family to a 5 0 -cap structure is an important first step in the protein synthesis of eukaryotic mRNA. It was recently demonstrated that the interaction between potyviral VPg and the eIF4E family is necessary for virus infection. In vitro analyses in this study showed that TuMV VPg specifically interacted with eIF(iso)4E and that its binding affinity was stronger than that of eIF(iso)4E and capped RNA. Additionally, VPg can form a ternary complex with the eIF(iso)4G mediate eIF(iso)4E. These results suggest that VPg can interfere with the translation of host cellular mRNA and may participate in translational initiation of viral RNA.