Development of CoQ10-enriched rice from giant embryo lines

Coenzyme Q (CoQ), also called ubiquinone, is an electron transfer molecule in the respiratory chain; it is also a lipid-soluble antioxidant. Most cereal crops produce mainly CoQ9, which has nine isoprene units, whereas humans produce mainly CoQ10, with 10 isoprene units. CoQ10 is a very popular food supplement. Using the cultivar Nipponbare, we previously produced CoQ10-enriched rice plants (Nipponbare-type CoQ10-enriched rice plants) by introduction of the gene for decaprenyl diphosphate synthase (DdsA). In Nipponbare-type CoQ10-enriched rice plants, seed CoQ10 content per weight was increased to up to 10 times that of wild-type rice. However, seed CoQ10 level of those rice plants is still insufficient for practical use, and further 10-times increase in CoQ10 content have been expected. Here, we confirmed preferential accumulation of CoQ in bran and germ of rice seed, and produced improved CoQ10-enriched rice plants by using 2 kinds of giant embryo rice lines, Haiibuki and Chukei-toku 70 (Toku 70). In giant embryo line-type CoQ10-enriched rice plants, seed CoQ10 content per weight was increased to up to 1.4 times (Haiibuki-type) or 1.8 times (Toku 70-type) that in Nipponbare-type CoQ10-enriched rice plants, demonstrating that use of giant embryo rice lines is effective to increase seed CoQ10 content per weight.