Table

Some Genetically Modified Plants for Carotenoid Production

Model

Tomato fruits

Tobacco

Gene

Plant phytoene synthase

Bacterial phytoene synthase, crt B gene from Erwinia Bacterial phytoene desaturase (crtI) under the 35S promoter of the cauliflower mosaic virus Plant phytoene and Z-carotene desaturases Plant cyclases, Lcy-b, or Cyc-b gene, the last one obtained from the Beta mutant

Canola (Brassica napus)

Rice

Phytoene synthase (crtB) from Erwinia; the seed-specific promoter of Brassica napin was used

Phytoene synthase from daffodil

Daffodil phytoene synthase and lycopene cyclase, under the regulation of the endosperm-specific promoter of the glutelin gene and the bacterial phytoene desaturase (crtI) under the control of the 35S promoter

P-C-4-oxygenase from H. pluvialis (CrtO)

Phenotype

Dwarfism by the redirection of the synthesis from GGPP into carotenoid biosynthesis; fruits produced lycopene earlier than the wild-type plants, but final lycopene concentrations were lower Total carotenoids were increased twofold, in a fruit-specific manner P-Carotene content was tripled but total carotenoid concentration was halved

Threefold increase of P-carotene, but total carotenoids decreased Lyc-b produces a 3.8-fold increase in the P-carotene concentration; total carotenoid content was unchanged or slightly elevated; a greater boost was obtained with the transgenic expression of the Cyc-b in a manner that resembles the situation in the Beta mutant In mature seeds, the content of carotenoids was increased (mainly the a- and P-carotene) up to 50-fold, reaching 1600 ng/g fresh weight Increments in phytoene content Rice seeds expressing the Psy and crtI were yellow and contained P-carotene; interestingly, the presence of zeaxanthin and lutein was observed, rather than just lycopene

Tobacco accumulated a high concentration of ketocarotenoids, including astaxanthin, in the chromoplasts of the nectary tissue, changing the color flower from yellow to red; total carotenoids increased 140%

Sources: Adapted from Delgado-Vargas et al. (2000)2 and Hirshberg (2001).13

have been obtained (Table 7.8).213 Interestingly, it is estimated that over 124 million children worldwide are vitamin A deficient, and that improved vitamin A nutrition alone could prevent 1.3 to 2.5 million deaths among late infancy and preschool-age children that occur each year in developing countries. Consequently, one of the main goals is genetic modification of plants to obtain better sources of vitamin A.67 Accordingly, genetically modified plants have been developed to be improved vitamin

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