低毒病毒ORF B 6.4-7.0 kb区域调控病毒dsRNA积累

Hypoviruses are a group of unencapsidated, plus-stranded RNA viruses，which can attenuate the virulence of the chestnut blight fungus, Cryphonectria parasitica. Among these viruses, CHV1-Euro7 accumulates much more viral dsRNA in the host cells than CHV1-EP721 does. In this study, we constructed an in trans complementary plasmid 0.6GpCPXHY2 which contains a 0.6kb fragment between 6.4kb to 7.0 kb located in the ORF B of the CHV1-Euro7, and a similar plasmid, pCPTTP2, which contains an untranslatable form of the 0.6kb fragment by addition of double TAA terminator codons in front of the ATG triplet of the fragment. Then the two plasmids were introduced into the protoplasts of the EP721 separately. Transformants containing a normal form of the viral ORF B 6.4-7.0kb fragment increased the dsRNA level of CHV1-EP721 in the host, but transformants with the untranslatable form of the ORF B 6.4-7.0kb fragment failed to elevate the dsRNA accumulation level. These results demonstrate that 1) viral ORF B 6.4-7.0kb fragment is a determinant for viral dsRNA accumulation and 2) this determinant functions in form of protein. Our work lays a new foundation for elucidation of the mechanism of hypovirus dsRNA accumulation in the host cells.