Effect of disruption of the enniatin synthetase gene on the virulence of Fusarium avenaceum.

Production of the phytotoxic compound enniatin has been proposed to play a role during the infection process of plants by enniatin-synthesizing Fusarium species. Enniatins are cyclohexadepsipeptides synthesized by the multifunctional enzyme enniatin synthetase. To test the hypothesis that enniatin contributes to pathogenicity, enniatin-nonproducing mutants were constructed by gene disruption of the enniatin synthetase gene of a virulent Fusarium avenaceum strain. Four independent enniatin nonproducing mutants were characterized that did not express enniatin synthetase, as proved by RNA and protein blot analysis. The virulence on potato tuber tissue of the enniatin-nonproducing strains was significantly reduced compared with the virulence of the parent strain and three enniatin-producing transformants. Therefore, we conclude that enniatin production contributes to the virulence of Fusarium avenaceum.