Identification of the Wheat Signaling Proteins Interacting with the Fusarium Resistance Orphan Protein TaFROG and Characterization of Their Contribution to Plant Resistance to Fusarium graminearum and the Mycotoxin Deoxynivalenol

All genomes encode taxonomically restricted 'orphan' genes, the vast majority are of unknown function and not encoding previously identified protein domains. We previously reported the functional characterization of a Pooideae orphan gene (designated TaFROG) as a component of resistance to the globally important wheat disease, Fusarium head blight (FHB). In this study we want to determine the biochemical means by which TaFROG enhances plant disease resistance. TaFROG is an intrinsically disordered protein suggesting that it’s a component of the cellular signaling machinery. Therefore we conduct a yeast two-hybrid screen and identified putative wheat interacting proteins. This includes a Triticum specific NAC-like transcription factors and an evolutionarily conserved kinase SnRK1 (SNF1-Related Kinase 1), central integrators of stress and energy signaling. In planta bi-molecular fluorescence complementation assays confirmed these interactions. Gene expression studies showed that TaFROG is a component of the early wheat response to F. graminearum the causal fungal agent of FHB and its associated mycotoxic virulence factor deoxynivalenol (DON). In contrast, SnRK1 isn’t responsive to these stimuli at the gene expression level, but kinase activity analysis suggest that F. graminearum reduces SnRK1 activity whereas DON increases it. Using virus-induced gene silencing we present evidence that SnRK1a contributes to resistance to DON in a toxin/FHB resistant wheat genotype. Thus we conclude that TaFROG orphan protein interacts with a taxonomically restricted and an evolutionary conserved signaling proteins. Moreover the common role of TaFROG and SnRK1 in DON tolerance and their physical interaction suggest that they act together in the same signaling pathway.