‘First blue chrysanthemum engineered’

Truly blue chrysanthemum – photo: Naonobu Noda/NARO

Truly blue chrysanthemum – photo: Naonobu Noda/NARO

“We achieved the development of blue color in chrysanthemum by a two-step modification of the anthocyanin structure. This simple method is a promising approach to generate blue flowers in various ornamental plants by metabolic engineering”, state Japanese scientists Naonobu Noda, Satoshi Yoshioka, Sanae Kishimoto, Masayoshi Nakayama, Mitsuru Douzono, Yoshikazu Tanaka and Ryutaro Aida. The researchers work at Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization and the Research Institute of Suntory Global Innovation Center Limited, Suntory World Research Centre in Japan.
‘Most blue-hued flowers contain delphinidin-based anthocyanins’
In the abstract of their article in Science Advanced the authors memorize that various coloured cultivars of ornamental flowers have been bred by hybridization and mutation breeding. “However, the generation of blue flowers for major cut flower plants, such as roses, chrysanthemums, and carnations, has not been achieved by conventional breeding or genetic engineering. Most blue-hued flowers contain delphinidin-based anthocyanins; therefore, delphinidin-producing carnation, rose, and chrysanthemum flowers have been generated by overexpression of the gene encoding flavonoid 3′,5′-hydroxylase (F3′5′H), the key enzyme for delphinidin biosynthesis. Even so, the flowers are purple/violet rather than blue. To generate true blue flowers, blue pigments, such as polyacylated anthocyanins and metal complexes, must be introduced by metabolic engineering; however, introducing and controlling multiple transgenes in plants are complicated processes.”
The researchers succeeded in generating blue chrysanthemum flowers by the introduction of butterfly pea UDP (uridine diphosphate)–glucose:anthocyanin 3′,5′-O-glucosyltransferase gene, in addition to the expression of the Campanula medium F3′5′H. Newly synthesized 3′,5′-diglucosylated delphinidin-based anthocyanins exhibited a violet colour under the weakly acidic pH conditions of flower petal juice and showed a blue colour only through intermolecular association, termed ‘copigmentation’, with flavone glucosides in planta. [read the full article in Science Advanced].