Trichothecene mycotoxins such as deoxynivalenol (DON) are virulence factors of Fusarium graminearum, which causes Fusarium head blight, one of the most important diseases of small grain cereals. We previously identified a nonspecific lipid transfer protein (nsLTP) gene, AtLTP4.4, which was overexpressed in an activation-tagged Arabidopsis line resistant to trichothecin, a type B trichothecene in the same class as DON. Here we show that overexpression of AtLTP4.4 in transgenic wheat significantly reduced F. graminearum growth in 'Bobwhite' and 'RB07' lines in the greenhouse and reduced fungal lesion size in detached leaf assays. Hydrogen peroxide accumulation was attenuated on exposure of transgenic wheat plants to DON, indicating that AtLTP4.4 may confer resistance by inhibiting oxidative stress. Field testing indicated that disease severity was significantly reduced in two transgenic 'Bobwhite' lines expressing AtLTP4.4. DON accumulation was significantly reduced in four different transgenic 'Bobwhite' lines expressing AtLTP4.4 or a wheat nsLTP, TaLTP3, which was previously shown to have antioxidant activity. Recombinant AtLTP4.4 purified from Pichia pastoris exhibited potent antifungal activity against F. graminearum. These results demonstrate that overexpression of AtLTP4.4 in transgenic wheat suppresses DON accumulation in the field. Suppression of DON-induced reactive oxygen species by AtLTP4.4 might be the mechanism by which fungal spread and mycotoxin accumulation are inhibited in transgenic wheat plants.
Keywords: Fusarium head blight; ROS; Triticum aestivum; genetics and resistance; mycology; nsLTP; plant stress and abiotic disorders; trichothecene.