ORIGINAL PAPER Improvement of vitamin E quality and quantity in tobacco and lettuce by chloroplast genetic engineering

tant lipid-soluble antioxidant synthesized in chloro-plasts. Among the 8 isoforms of vitamin E, a-Toc has the highest activity in humans. To generate transgenic plants with enhanced vitamin E activity, we applied a chloroplast transformation technique. Three types of the transplastomic tobacco plants (pTTC, pTTMT and pTTC-TMT) carrying the Toc cyclase (TC) or c-Toc methyltransferase (c-TMT) gene and the TC plus c-TMT genes as an operon in the plastid genome, respectively, were generated. There was a significant increase in total levels of Toc due to an increase in c-Toc in the pTTC plants. Compared to the wild-type plants, Toc composition was altered in the pTTMT plants. In the pTTC-TMT plants, total Toc levels increased and a-Toc was a major Toc isoform. Furthermore, to use chloroplast transformation to produce a-Toc-rich vegetable, TC-overexpressing transplastomic lettuce plants (pLTC) were generated. Total Toc levels and vitamin E activity increased in the pLTC plants compared with the wild-type lettuce plants. These findings indicated that chloroplast genetic engineering is useful to improve vitamin E quality and quantity in plants