We provide evidence that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying serine to roots. Serine supplementation to the growth medium rescues root developmental arrest and restores normal levels of carbohydrates and sugar biosynthetic activities in gapcp double mutants. We demonstrate that GAPCps are important for the synthesis of serine in roots. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In this work, we have identified two Arabidopsis ( Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). However, the in vivo functions of the plastidial isoforms remain unresolved.
Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described.
The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD + to NADH. Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids.
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