Specific binding of Fusarium graminearum Hex1 protein to untranslated regions of the genomic RNA of Fusarium graminearum virus 1 correlates with increased accumulation of both strands of viral RNA.

The HEX1 gene of Fusarium graminearum was previously reported to be required for the efficient accumulation of Fusarium graminearum virus 1 (FgV1) RNA in its host. To investigate the molecular mechanism underlying the production of FgHEX1 and the replication of FgV1 viral RNA, we conducted electrophoretic mobility shift assays (EMSA) with recombinant FgHex1 protein and RNA sequences derived from various regions of FgV1 genomic RNA. These analyses demonstrated that FgHex1 and both the 5'- and 3'-untranslated regions of plus-strand FgV1 RNA formed complexes. To determine whether FgHex1 protein affects FgV1 replication, we quantified accumulation viral RNAs in protoplasts and showed that both (+)- and (-)-strands of FgV1 RNAs were increased in the over-expression mutant and decreased in the deletion mutant. These results indicate that the FgHex1 functions in the synthesis of both strands of FgV1 RNA and therefore in FgV1 replication probably by specifically binding to the FgV1 genomic RNA.