Plastidial glycolysis in developing Arabidopsis embryos.

During oilseed embryo development, carbon from sucrose is utilized for fatty acid synthesis in the plastid. The role of plastidial glycolysis in Arabidopsis embryo oil accumulation was investigated. Genes encoding enolases (ENO) and phosphoglyceromutases (PGlyM) were identified, and activities and subcellular locations were established by expression of recombinant and green fluorescent protein (GFP)-fusion proteins. Mutant Arabidopsis plants lacking putative plastidial isoforms were characterized with respect to isoform composition and embryo oil content. In the developing embryo, ENO1 and ENO2 account for most or all of the plastidial and cytosolic ENO activity, respectively, and PGLYM1 accounts for most or all of the plastidial PGlyM activity. The eno1 and pglym1 mutants, in which plastidic ENO and PGlyM activities were undetectable, had wild-type amounts of seed oil at maturity. It is concluded that although plastids of developing Arabidopsis embryos have the capacity to carry out the lower part of the glycolytic pathway, the cytosolic glycolytic pathway alone is sufficient to support the flux from 3-phosphoglycerate to phosphoenolpyruvate required for oil production. The results highlight the importance for oil production of translocators that facilitate interchange of glycolytic intermediates between the cytosol and the plastid stroma.