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

Abstract

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 c-tocopherol methyltransferase (c-TMT) gene under the control of seed-specific vicillin promoter. Molecular characterization including PCR, Southern and Northern blots confirmed that the c-TMT transgene was successfully inherited to and expressed in the progeny plants. The c -TMT transgene was specifically expressed in immature seeds of transgenic plants, leading to efficient conversion of c-tocopherol to a-tocopherol and dramatic increase in seed a-tocopherol content, as detected by high performance liquid chromatography analysis. We also showed that such a high a-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 c-TMT gene in transgenic perilla displaying desirable high a-tocopherol content phenotype. Since a-tocopherol has the highest vitamin E activity, the transgenic perilla with high a-tocopherol content in seeds developed in this study will benefit both human and animal health.

Methodology Molecular cloning and characterization of gene coding for γ-tocopherol methyltransferase from lettuce (Lactuca sativa)

“…So far, the γ-TMT gene has been cloned from Arabidopsis thaliana, Brassica napus, Triticum aestivum, Helianthus annuus, and many other plants. The overexpression of the γ-TMT gene (mostly from A. thaliana) has been reported in Perilla frutescens, Lactuca sativa, Brassica juncea, Codonopsis lanceolata, and in soybean seed (Van Eenennaam et al, 2003;Cho et al, 2005;Yusuf and Sarin, 2007;Lee et al, 2008;Seong et al, 2009), which demonstrated the increase of α-tocopherol. In this study, the gene encoding γ-tocopherol methyltransferase, LsTMT, was cloned from L. sativa for the first time.…”

Current strategies for vitamin E biofortification of crops

“…While g-tocopherol dominated the tocopherol composition of wild-type seeds (>95%), a-tocopherol represented up to 95% of seed tocopherols in the best transgenic event [23]. Subsequently, the successful conversion of g-tocopherol into a-tocopherol via g-TMT overexpression has been reported in many other plants including soybean [24][25][26][27], shiso [28], lettuce [29], mustard [30], maize [31], and tobacco [32]. Because of the higher biological activity of a-tocopherol, most g-TMT overexpressing crops exhibited 5-10 times higher vitamin E activity than untransformed plants.…”

Uses and Values of Perilla (Perilla frutescens var. frutescens) as a Functional Oil Source

“…일반적으로 tocopherol 이성체는 α > β > γ > δ-isomer의 순으로 항산화 능력이 평가되었다 (Haung et al, 1994). Lee et al (2008) 계열의 유지를 혼합하여 ω-6/ω-3 비율을 조절하여 들깨유의 취약성을 개선할 수 있을 것으로 보인다 (Kim et al, 1996;Kim et al, 1999b;Lee et al, 2012). …”