Antioxidant value addition in human diets: genetic transformation of Brassica juncea with gamma-TMT gene for increased alpha-tocopherol content.

Alpha-tocopherol, the most biologically active form of vitamin E, is implicated in decreasing the risk of several types of cancers, coronary heart disease and a number of degenerative human conditions, when taken in excess of the recommended daily allowance. Natural alpha-tocopherol has twice the bioavailability of the synthetic isomer. This study describes a successful attempt at fortifying human diets with natural alpha-tocopherol by taking recourse to genetic engineering of an important oilseed crop, Brassica juncea. Gamma-tocopherol methyl transferase cDNA from Arabidopsis thaliana, coding for the enzyme catalysing the conversion of the large gamma-tocopherol pool to alpha-tocopherol, was overexpressed in B. juncea plants. The successful integration of the transgene was confirmed by PCR and Southern blot analysis, while the enhanced transcript level was evident in the northern blot analysis. HPLC analysis of the seeds of the T1 transgenic lines showed a shift in tocopherol profile with the highest over-expressors having alpha-tocopherol levels as high as sixfold over the non-transgenic controls. This study discusses the production of a transgenic oilseed crop with high alpha-tocopherol levels, which can provide a feasible, innocuous, and inexpensive way of taking the beneficial effects of high alpha-tocopherol intake to the masses.