Expression of gamma-Tocopherol Methyltransferase Transgene Improves Tocopherol Composition in Lettuce (Latuca sativa L.)

A cDNA encoding γ-tocopherol methyltransferase (γ-TMT) from Arabidopsis thaliana was overexpressed in lettuce (Latuca sativa L.) to improve the tocopherol composition. Seven lines of lettuce (T0) containing the γ-TMT transgene were produced by Agrobacteriummediated transformation. The inheritance and expression of the transgene were confirmed by DNA and RNA gel blot analyses as well as quantification of tocopherols and γ-TMT activities. The ratio of α-/γ- tocopherol content (TR) varied from 0.6 to 1.2 in nontransformed plants, while the T0 plants had ratios of 0.8 to 320. The ratio ranged from 0.4 to 544 in 41 T1 progenies of the T0 transgenic line gTM3, and the phenotypic segregation indicated monogenic inheritance of the transgene (i.e., 3:1 = dominant:wild-type classes). There was a tight relationship between the TR phenotype and γ-TMT activity, and enzyme activities were affected by the copy number and transcript levels of the transgene. The TR phenotype was stably expressed in T2 progenies of T1 plants. The results from this study indicated that a stable inheritance and expression of Arabidopsis γ-TMT transgene in lettuce results in a higher enzyme activity and the conversion of the γ-tocopherol pool to α-tocopherol in transgenic lettuce. KCI Citation Count: 45