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Combinatorial genetic transformation generates a library of metabolic phenotypes for the carotenoid pathway in maize
- Zhu, Changfu, Naqvi, Shaista, Breitenbach, Jürgen, Sandmann, Gerhard, Christou, Paul, Capell, Teresa
- Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.47 pp. 18232-18237
- genetic transformation, gene transfer, Zea mays, biosynthesis, recombinant DNA, transgenic plants, corn, beta-carotene, endosperm, genes, promoter regions
- Combinatorial nuclear transformation is a novel method for the rapid production of multiplex-transgenic plants, which we have used to dissect and modify a complex metabolic pathway. To demonstrate the principle, we transferred 5 carotenogenic genes controlled by different endosperm-specific promoters into a white maize variety deficient for endosperm carotenoid synthesis. We recovered a diverse population of transgenic plants expressing different enzyme combinations and showing distinct metabolic phenotypes that allowed us to identify and complement rate-limiting steps in the pathway and to demonstrate competition between β-carotene hydroxylase and bacterial β-carotene ketolase for substrates in 4 sequential steps of the extended pathway. Importantly, this process allowed us to generate plants with extraordinary levels of β-carotene and other carotenoids, including complex mixtures of hydroxycarotenoids and ketocarotenoids. Combinatorial transformation is a versatile approach that could be used to modify any metabolic pathway and pathways controlling other biochemical, physiological, or developmental processes.