WIN1 Transcription Factor Channelizes Free Fatty Acids to Enforce Cuticle in Barley Spikelets to Resist Fusarium Head Blight

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe (Teleomorph: Gibberella zeae) is one of the most devastating diseases that severely affects crop production. Resistance to FHB is highly complex and quantitative in nature and is majorly classified as type-I (resistance to initial infection of spikelets), and type-II (resistance to spread within the spike or rachis resistance). Barley has high level of type-II resistance. In the present study, two two-row barley cultivars viz. CI9831 (R=resistant), and H106-371 (S=susceptible) varying in resistance to FHB were selected to identify the resistance related (RR) metabolites. Using non-targeted metabolomics approach (LC-ESI-LTQ-Orbitrap), key RR metabolites belonging to fatty acids, phenylpropanoids, flavonoids and terpenoid biosynthetic pathways were identified. The free fatty acids: Linoleic and palmitic acid, were among the highest fold change resistance related induced (RRI) metabolites. The role of these FFAs was proposed to be in cuticle biosynthesis, which acts as a barrier for the entry of pathogen thereby conferring resistance to host. Quantitative-real time PCR studies revealed higher expressions of CYP86A2, and CYP89A2, LACS-2, GPAT-6 and WIN1 transcription factor (TF) genes, involved in the cuticle biosynthesis, in the pathogen-inoculated resistant genotype than in susceptible. Sequencing of WIN1 TF showed the absence of first intron in the susceptible genotype. Further, silencing of WIN1 by virus induced gene silencing in resistant genotype showed increased fungal biomass and decreased abundance of FFA like linoleic, palmitic acid upon pathogen inoculation, proving the link of WIN1 in regulating genes involved in cuticle biosynthesis.