Identification of regulated proteins in naked barley grains (Hordeum vulgare nudum) after Fusarium graminearum infection at different grain ripening stages

We analyzed the effect of Fusarium graminearum infection on field-grown naked barley (Hordeum vulgare nudum). The ears were inoculated with F. graminearum spores during anthesis. In the course of ripening, grains in five phenological growth stages of naked barley from milk ripe to plant death were sampled. The albumin and globulin proteins of inoculated grains and untreated (control) grains were separated by two-dimensional gel electrophoresis. Forty-five spots composing of proteins that were changed in abundance due to F. graminearum infection were subsequently identified by mass spectrometry. Various proteins showing altered expression pattern after Fusarium infection were linked to stress response such as plant signal transduction pathways, fungal defense and oxidative burst. More proteins changed during early grain ripening stages than during later ripening stages. Protease inhibitors occurred at increased abundancy during milk ripe stage. A thaumatin-like protein accumulated at plant death stage. Proteins linked to nitrogen metabolism and protein biosynthesis were mainly reduced, whereas those linked to carbon metabolism were predominantly increased in infected grains. Biological significance: Fusarium graminearum infection can lead to significant contamination of grains with mycotoxins. With this 2D-based proteomics study we give an insight into plant-pathogen interactions between the non-model plant naked barley and the fungus F. graminearum during five stages of grain development. Over the multiple developmental stages we observed specific patterns of changes induced by the fungus: the primary plant metabolism and inhibition of fungal protease were predominantly affected during early grain development stages. During the entire grain development we found an induced accumulation of thaumatinlike proteins due to the fungal infection indicating their fundamental role for naked barley defense.