Enhancement of Nutritional Quality of Wheat (Triticum aestivum) by Metabolic Engineering of Isoflavone Pathway

Isoflavones are large group of secondary metabolites produced in legumes such as soybeans. They have essential biological functions as nutraceutical and health functions for human. They are involved in plant resistance to biotic and abiotic stresses, symbiotic relationship with nitrogen-fixing organisms and plant competition (allelopathy). In this report, isoflavonoids were expressed in wheat (Triticum aestivum) via introducing the key enzymes Isoflavone Synthase (IFS). Transgenic callli induced from wheat immature embryos were propagated and prepared for bombardment. Five gene constructs were prepared; the binary vector (plasmid) pAHC25, 35S-CRC, 35S-IFS, Oleocin-IFS, Oleocin-IFS-CHI and were used for wheat calli transformation. Putative transgenic calli were used to regenerate transgenic wheat plants. Evaluation of recovered transgenic plants was carried out using PCR, southern bloting of PCR products and IFS-specific probe and HPLC analysis of transgenic plant tissue extracts. Genistein and naranigenin were detected in transgenic plants carrying IFS gene, indicating that the introduced IFS was able to use the endogenous substrate from wheat. IFS showed activity under 35S promoter as well as oleocin promoter. The activity of oleocin promoter in monocots provides a good tool to use plant promoters to drive plant gene expression in plants. This also represents promoter compatibility that the cis acting elements of the oleocin promoter represent binding targets for trans acting elements of wheat. Engineering the isoflavone pathway in wheat would lead to enhancement of nutraceutical value of wheat grains and improvement of wheat resistance to diseases.