Two papers in this issue improve on nature by engineering carotenoid biosynthetic pathways. In the first, Albrecht et al. have transformed Escherichia coli with carotenoid genes from two other bacteria capable of inducing expression of diverse carotenoid structures. They thus provide E. coli with the enzymes necessary to produce phytoene (C40), the universal starting compound for carotenoid synthesis. By introducing additional enzymes involved in the production of carotenoid intermediates, they obtained a diverse range of products, among them several unique acyclic hydroxyl-containing carotenoids. The superior antioxidant activity of these new carotenoids was demonstrated using a liposome–membrane model system (p. 843).

Taking an alternative approach, on p. 888, Mann et al. have engineered the tobacco carotenoid biosynthetic pathway to produce the marine compound astaxanthin, a red pigment of considerable economic and nutritional value because of its antioxidant properties. By introducing a β-carotene ketolase from the alga Haematococcus pluvialis into tobacco under the control of a gene promoter for flower petal expression, they succeeded in synthesizing astaxanthin from the endogenous β-carotene in the flower nectary. Astaxanthin and other ketocarotenoids accumulating in the flowers changed their color from yellow to red. (See also p. 825).