import of phosphoenolpyruvate by plastids from developing embryos of oilseed rape, Brassica napus (L.), and its potential as a substrate for fatty acid synthesis

• Published in: Journal of experimental botany Vol. 55; no. 402; pp. 1455 - 1462
• Main Authors: Kubis, S.E, Pike, M.J, Everett, C.J, Hill, L.M, Rawsthrone, S
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.07.2004; Oxford Publishing Limited (England)
• Subjects: Base Sequence; biochemical pathways; Biological and medical sciences; Biological Transport; biosynthesis; Brassica napus; Brassica napus - genetics; Brassica napus - physiology; Brassica napus var. napus; Carbon; Cell physiology; Cloning, Molecular; DNA Primers - genetics; embryo; embryo (plant); embryogenesis; Embryos; enzyme substrates; fatty acid synthesis; Fatty acids; Fatty Acids - biosynthesis; Fundamental and applied biological sciences. Psychology; gene expression; glucose 6-phosphate; Imports; Leaves; Lipid metabolism; lipogenesis; metabolites; Oilseeds; Phosphates; phosphoenolpyruvate; Phosphoenolpyruvate - metabolism; phosphoenolpyruvate translocator; Plant physiology; Plant physiology and development; plasma membrane; Plasma membrane and permeation; plastid; Plastids; Plastids - metabolism; pyruvic acid; Pyruvic Acid - metabolism; rapeseed; Research Papers: Cell and Molecular Biology, Biochemistry and Molecular Physiology; Reverse Transcriptase Polymerase Chain Reaction - methods; Seeds - physiology; transporters; Brassica napus var. oleifera; embryo; phosphoenolpyruvate translocator; Plant leaf; Plastid; Metabolism; Fatty acids; fatty acid synthesis; Cruciferae; Dicotyledones; Angiospermae; Brassica napus; Development; Spermatophyta; ATP
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erh157

The plastidial phosphoenolpyruvate (PEP)/phosphate translocator (PPT) is expressed in the developing embryos of oilseed rape (Brassica napus L.). PEP can be imported by plastids isolated from embryos and used for fatty acid synthesis at rates that are sufficient to account for one-third of the rate of fatty acid synthesis in vivo. This provides the first experimental evidence for uptake of PEP and incorporation of carbon from it into fatty acids by plastids. PEP metabolism in isolated plastids is able to provide some of the ATP required for fatty acid synthesis. Expression of the PPT and related glucose 6-phosphate (Glc-6-P) translocator (GPT) is high in early embryo and leaf development and then declines. The marked decline in the abundance of PPT and GPT transcripts between the pre- and mid-oil accumulating stages of embryo development in B. napus does not correlate with the corresponding translocator activities, which both increase over the same period. This means that transcript abundance cannot be used to infer the activity of the translocators.