Increased α-tocotrienol content in seeds of transgenic rice overexpressing Arabidopsis γ-tocopherol methyltransferase
- 870 Downloads
Vitamin E comprises a group of eight lipid soluble antioxidant compounds that are an essential part of the human diet. The α-isomers of both tocopherol and tocotrienol are generally considered to have the highest antioxidant activities. γ-tocopherol methyltransferase (γ-TMT) catalyzes the final step in vitamin E biosynthesis, the methylation of γ- and δ-isomers to α- and β-isomers. In present study, the Arabidopsis γ-TMT (AtTMT) cDNA was overexpressed constitutively or in the endosperm of the elite japonica rice cultivar Wuyujing 3 (WY3) by Agrobacterium-mediated transformation. HPLC analysis showed that, in brown rice of the wild type or transgenic controls with empty vector, the α-/γ-tocotrienol ratio was only 0.7, much lower than that for tocopherol (~19.0). In transgenic rice overexpressing AtTMT driven by the constitutive Ubi promoter, most of the γ-isomers were converted to α-isomers, especially the γ- and δ-tocotrienol levels were dramatically decreased. As a result, the α-tocotrienol content was greatly increased in the transgenic seeds. Similarly, over-expression of AtTMT in the endosperm also resulted in an increase in the α-tocotrienol content. The results showed that the α-/γ-tocopherol ratio also increased in the transgenic seeds, but there was no significant effect on α-tocopherol level, which may reflect the fact that γ-tocopherol is present in very small amounts in wild type rice seeds. AtTMT overexpression had no effect on the absolute total content of either tocopherols or tocotrienols. Taken together, these results are the first demonstration that the overexpression of a foreign γ-TMT significantly shift the tocotrienol synthesis in rice, which is one of the world’s most important food crops.
KeywordsVitamin E Transgenic rice γ-tocopherol methyltransferase α-tocotrienol α-tocopherol
This study was supported by the National Key Basic Research Projects (2012CB944803), the National Special Program for Transgenic Research (2011ZX08001-006), and the Funds for Distinguished Young Scientists and Priority Academic Program Development from Jiangsu Government, China.
- Farré G, Sudhakar D, Naqvi S, Sandmann G, Christou P, Capell T, Zhu C (2012) Transgenic rice grains expressing a heterologous ρ-hydroxyphenylpyruvate dioxygenase shift tocopherol synthesis from the γ to the α isoform without increasing absolute tocopherol levels. Transgenic Res. doi: 10.1007/s11248-012-9601-7
- Liu QQ, Zhang JL, Wang ZY, Hong MM, Gu MH (1998) A highly efficient transformation mediated by Agrobacterium in rice. Acta Phytophysiol Sin 24:259–271Google Scholar
- Padley FB, Gunstone FD, Harwood JL (1994) Occurrence and characteristics of oils and fats. In: Gunstone FD, Harwood JL, Padley FB (eds) The lipid handbook, 2nd edn. Chapman & Hall, London, pp 127–130Google Scholar
- Rink C, Christoforidis G, Khanna S, Peterson L, Patel Y, Khanna S, Abduljalil A, Irfanoglu O, Machiraju R, Bergdall VK, Sen CK (2011) Tocotrienol vitamin E protects against preclinical canine ischemic stroke by inducing arteriogenesis. J Cereb Blood Flow Metab 31:2218–2230PubMedCrossRefGoogle Scholar
- Sheppard AJ, Pennington JAT, Weihrauch JL (1993) Analysis and distribution of vitamin E in vegetable oils and foods. In: Packer L, Fuchs J (eds) Vitamin E in health and disease. Marcel Dekker, New York, pp 9–31Google Scholar
- Yuen KH, Wong JW, Lim AB, Ng BH, Choy WP (2011) Effect of mixed-tocotrienols in hypercholesterolemic subjects. Funct Foods Health Dis 3:106–117Google Scholar
- Zhang GY, Liu RR, Zhang P, Xu Y, Zhu J, Gu MH, Liang GH, Liu QQ (2012) Variation and distribution of vitamin E and composition in the seeds among different rice varieties. Acta Agrono Sin 38:55–61Google Scholar
- Zheng FQ, Wang ZY, Gao JP (1993) Isolation of total RNA from rice endosperm. Plant Physiol Commun 29:438–440Google Scholar