Identification and molecular characterization of flavonoid biosynthetic genes and their expression analysis in wheatgrass (Triticum aestivum L.) during leaf rust infection

Wheat (Triticum aestivum L.) is a major staple food worldwide. Puccinia triticina forms infectious urediniospores causing leaf rust disease in bread wheat leading to an annual yield loss of ~ 15% globally. Evolution of new virulent strains and ability of urediniospores to traverse long distances in air pose a challenge on the prevailing leaf rust control techniques. Therefore, significant knowledge is required about the genes in wheat plants that can restrict disease development. Contemporary studies indicate that flavonoid biosynthetic genes are involved in transcriptional and post-transcriptional gene regulation, growth, responses to environmental stimuli, and signal transduction. We were able to identify flavonoids like apigenin and luteolin that were synthesized in wheat plants only after leaf rust infection In silico identification of contigs from four SOLiD-SAGE libraries and their functional annotation depicted the involvement of secondary metabolism pathways in retort to the disease development. The flavonoid biosynthetic pathway was discerned through KEGG mapping of the identified contigs and the key genes like Chalcone synthase, Flavanone 3-dioxygenase, and Anthocyanidin synthase were characterized. Expression analysis of these genes at varied time points post-pathogen infection on both resistant and susceptible wheat Near-Isogenic Lines revealed their association with development, metabolism, and defense response regulation. Expression of these genes decreased significantly during pathogenesis in susceptible wheat plants compared to the resistant plants, indicating the transition in expression of flavonol accumulation possibly to combat leaf rust disease progression. Consequently, this study focuses on investigating flavonoid biosynthetic genes in wheat and their response during leaf-rust pathogenesis.