Reduction of fumonisin production in Fusarium verticillioides by RNA interference

The fungus Fusarium verticillioides can produce fumonisin mycotoxins in ears under certain environmental conditions. Because fumonisins are unhealthy for humans and livestock, control strategies with nominal risk to the environment are needed to reduce fumonisin exposure. Host-induced gene silencing is a molecular engineered technique in which double-stranded RNA expressed in the plant host is absorbed by an invading fungus; subsequently, the expression of targeted genes is reduced in the fungus. A vital preliminary step of this technique is identification of DNA segments within the gene target that can effectively silence gene expression when expressed in the fungus. Here, we used segments of the fumonisin biosynthetic gene FUM1 to synthesize double-stranded RNA in F. verticillioides. Several of the resulting transformants had reduced FUM1 gene expression and fumonisin production. Similar losses in fumonisin production resulted from double-stranded RNA constructs with segments of FUM8, another fumonisin biosynthetic gene. FUM1 or FUM8 silencing constructs were transformed into three isolates of F. verticillioides originating from different regions of the United States. Whole genome sequence analysis of seven transformants indicated that reductions in fumonisin production were not due to mutation of the fumonisin biosynthetic gene cluster and showed a complex pattern of plasmid integration. These results indicate the cloned FUM1 or FUM8 gene segments could be transgenically expressed in maize for host-induced gene silencing of fumonisin production.