Seed specific expression of perilla γ-tocopherol methyltransferase gene increases α-tocopherol content in transgenic perilla (Perilla frutescens)

Increasing vitamin E activity in economically important oil crops such as perilla will enhance the nutritional value of these crops. Perilla (Perilla frutescens Britt) represents an important oil crop in Asian countries, including Korea. Using Agrobacterium-mediated transformation, we have engineered perilla with the gamma-tocopherol methyltransferase (gamma-TMT) gene under the control of seed-specific vicillin promoter. Molecular characterization including PCR, Southern and Northern blots confirmed that the gamma-TMT transgene was successfully inherited to and expressed in the progeny plants. The gamma -TMT transgene was specifically expressed in immature seeds of transgenic plants, leading to efficient conversion of gamma-tocopherol to alpha-tocopherol and dramatic increase in seed alpha-tocopherol content, as detected by high performance liquid chromatography analysis. We also showed that such a high alpha-tocopherol content phenotype was transmitted to the progeny plants. In addition, there was no significant change in fatty acid composition in transgenic seeds as compared with untransformed control Yeupsil cultivar, suggesting the lack of interplay between the fatty acid and tocopherol biosynthesis pathways. This was the first report on over expression of the gamma-TMT gene in transgenic perilla displaying desirable high alpha-tocopherol content phenotype. Since alpha-tocopherol has the highest vitamin E activity, the transgenic perilla with high alpha-tocopherol content in seeds developed in this study will benefit both human and animal health.