Combinatorial genetic transformation generates a library of metabolic phenotypes for the carotenoid pathway in maize.
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.
Zhu
Changfu
C
Departament de Producció Vegetal i Ciència Forestal, Universitat de Lleida, Avenue Alcalde Rovira Roure, 191, 25198 Lleida, Spain.
Naqvi
Shaista
S
Breitenbach
Jürgen
J
Sandmann
Gerhard
G
Christou
Paul
P
Capell
Teresa
T
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*
D002338:Carotenoids; D006899:Mixed Function Oxygenases; D010105:Oxygenases; C093259:beta-carotene ketolase; C079232:beta-carotene hydroxylase