Cloning, functional characterisation and transgenic manipulation of vitamin E biosynthesis genes of wheat.

Abstract

Tocochromanols are an important group of plastidic lipophilic antioxidants that form an essential part of human diet and play important functions in photosynthetic organisms by protecting them from photo-oxidation, lipid peroxidation and membrane damage. Molecular genetics and genomics-based approaches have revealed the genes required for synthesis of these compounds in model organisms like rice, Arabidopsis and Synechocystis. To create a positive impact on human nutrition and health, the levels of total and specific tocochromanols have been altered in various agricultural crops by metabolic engineering. To understand the mechanisms involved in higher tocochromanol levels of wheat seeds and its germ, the tocochromanol biosynthesis pathway was investigated in wheat. The focus of this research was towards isolation of genes involved in wheat tocochromanol biosynthesis, and homologous and heterologous transgenic manipulation to alter their content and composition. Functional characterisation of TaHydroxyphenylpyruvate dioxygenase and Taγ-Tocopherol methyltransferase-overexpressing transgenic Arabidopsis plants revealed alterations in tocochromanol content and composition, which suggests better growth of these plants in the presence of sorbitol. TaHydroxyphenylpyruvate dioxygenase-overexpressing transgenic wheat, Triticum aestivum L. plants also showed 2.4-fold increase in tocochromanol content, which may have nutritional as well as antioxidative roles. Further characterisation and field trials of these transgenic lines can provide us more insight about the antioxidative roles of tocochromanols.