title: Combinatorial genetic transformation generates a library of metabolic phenotypes for the carotenoid pathway in maize.
abstract: 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 beta-carotene hydroxylase and bacterial beta-carotene ketolase for substrates in 4 sequential steps of the extended pathway. Importantly, this process allowed us to generate plants with extraordinary levels of beta-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.
authors.affiliation: Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida, Avenue Alcalde Rovira Roure, 191, 25198 Lleida, Spain.
authors.forename: Changfu
authors.initials: C
authors.lastname: Zhu
authors.forename: Shaista
authors.initials: S
authors.lastname: Naqvi
authors.forename: Jürgen
authors.initials: J
authors.lastname: Breitenbach
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sandmann
authors.forename: Paul
authors.initials: P
authors.lastname: Christou
authors.forename: Teresa
authors.initials: T
authors.lastname: Capell
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D017343:Genes, Plant; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009154:Mutation; D010105:Oxygenases / Q000378:metabolism; D030821:Plants, Genetically Modified; D013379:Substrate Specificity; D014170:Transformation, Genetic; D003313:Zea mays / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D002338:Carotenoids; D006899:Mixed Function Oxygenases; D010105:Oxygenases; C093259:beta-carotene ketolase; C079232:beta-carotene hydroxylase