Fig. 6.

Simplified pathways illustrating carbon refixation by Rubisco in the plastid after labeling pennycress embryos with [U-¹³C₅]glutamine. Values next to brackets report the average labeling per carbon (%) of the molecule, whereas values next to carboxylic groups are the ¹³C enrichment (%) for the C1 of the molecules determined by LC-MS/MS. Gray and white spheres represent labeled and unlabeled carbon atoms, respectively. The shades of gray are proportional to the labeling. The carboxylic groups of methionine, valine, and phenylalanine are derived from those of malate, pyruvate, and phophoenolpyruvate, respectively. Abbreviations (in alphabetical order): AcCoA, acetyl-CoA; AKG, α-ketoglutarate; CIT, citrate; FUM, fumarate; GLYP, glycerol phosphate; ICIT, isocitrate; MAL, malate; OAA, oxaloacetate; PGA, phosphoglycerate; P5P, pentose 5-phosphates; PYR, pyruvate; Ru1,5BP, ribulose 1,5-bisphosphate; SUCC, succinate; TP, triose phophates; Vglycop, portion of pyruvate produced from the plastidic glycolysis; Vmep, portion of pyruvate produced by the plastidic NADP-dependent malic enzyme.