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An engineered phosphoenolpyruvate carboxylase redirects carbon and nitrogen flow in transgenic potato plants
Author(s) -
Rademacher Thomas,
Häusler Rainer E.,
Hirsch HeinzJosef,
Zhang Li,
Lipka Volker,
Weier Dagmar,
Kreuzaler Fritz,
Peterhänsel Christoph
Publication year - 2002
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2002.01397.x
Subject(s) - phosphoenolpyruvate carboxylase , genetically modified crops , nitrogen , transgene , carbon fibers , gene flow , agronomy , biology , environmental science , botany , chemistry , photosynthesis , materials science , biochemistry , gene , organic chemistry , composite number , composite material , genetic variation
Summary Phosphoenolpyruvate carboxylase (PEPC) plays a central role in the anaplerotic provision of carbon skeletons for amino acid biosynthesis in leaves of C 3 plants. Furthermore, in both C4 and CAM plants photosynthetic isoforms are pivotal for the fixation of atmospheric CO 2 . Potato PEPC was mutated either by modifications of the N‐terminal phosphorylation site or by an exchange of an internal cDNA segment for the homologous sequence of PEPC from the C 4 plant Flaveria trinervia . Both modifications resulted in enzymes with lowered sensitivity to malate inhibition and an increased affinity for PEP. These effects were enhanced by a combination of both mutated sequences and pulse labelling with 14 CO 2 in vivo revealed clearly increased fixation into malate for this genotype. Activity levels correlated well with protein levels of the mutated PEPC. Constitutive overexpression of PEPC carrying both N‐terminal and internal modifications strongly diminished plant growth and tuber yield. Metabolite analysis showed that carbon flow was re‐directed from soluble sugars and starch to organic acids (malate) and amino acids, which increased four‐fold compared with the wild type. The effects on leaf metabolism indicate that the engineered enzyme provides an optimised starting point for the installation of a C 4 ‐like photosynthetic pathway in C 3 plants.