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The characteristic yellow-orange color of Cheez Whiz comes from a natural plant pigment, the carotenoid bixin. Known in crude extract as annatto, bixin is isolated from the seeds of the tropical plant Bixa orellana. Researchers have now determined how the shrub synthesizes bixin from another carotenoid, lycopene, and are planning to use that knowledge to engineer bixin-producing tomatoes. the group hypothesized that the structural similarity between bixin and saffron meant a similar biosynthetic pathway. They used DNA probes crafted from the genes of other plants to look for similar sequences in B. orellana. They found the enzyme pathway they were looking for: a dioxygenase to convert lycopene to bixin aldehyde, then an aldehyde dehydrogenase to produce norbixin, and finally a methyltransferase to yield bixin. The researchers transferred the relevant B. orellana genes into bacteria preengineered to produce lycopene and were able to detect bixin production.
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