An ABC-B Transporter Helps Protect Fusarium graminearum Against Enniatin Toxicity

Fusarium graminearum and F. avenaceum often co-contaminate Canadian durum wheat grain, resulting in the co-deposition of species-specific mycotoxins, including trichothecenes produced by F. graminearum and enniatins produced by F. avenaceum. These mycotoxins pose significant risks to human and animal health. Although these fungi commonly co-occur in infected wheat, relatively little is known about how they interact during host infection. Interactions between the two species were examined using co-inoculation experiments on durum wheat spikes. In pathology trials, co-inoculations often reduced both disease severity and trichothecene accumulation compared with inoculations of F. graminearum alone, despite F. graminearum greatly out-competing F. avenaceum in total fungal biomass. Transcriptomic profiling identified strong induction of the F. graminearum ABC transporter gene FgABCB8 during co-inoculation with an enniatin-producing F. avenaceum strain. When F. graminearum was grown in vitro, FgABCB8 was induced upon exposure to F. avenaceum culture filtrate, or the related cyclohexadepsipeptides enniatin B1 or beauvericin. Heterologous expression of FgABCB8 in yeast provided partial protection against enniatin and beauvericin toxicity. Gene disruption of FgABCB8 increased F. graminearum sensitivity to enniatins. These findings demonstrate that FgABCB8 expression enhances the ability of F. graminearum to tolerate enniatin-producing fungi.