title: Chloroplast-localized 6-phosphogluconate dehydrogenase is critical for maize endosperm starch accumulation.
abstract: Plants have duplicate versions of the oxidative pentose phosphate pathway (oxPPP) enzymes with a subset localized to the chloroplast. The chloroplast oxPPP provides NADPH and pentose sugars for multiple metabolic pathways. This study identified two loss-of-function alleles of the Zea mays (maize) chloroplast-localized oxPPP enzyme 6-phosphogluconate dehydrogenase (6PGDH). These mutations caused a rough endosperm seed phenotype with reduced embryo oil and endosperm starch. Genetic translocation experiments showed that pgd3 has separate, essential roles in both endosperm and embryo development. Endosperm metabolite profiling experiments indicated that pgd3 shifts redox-related metabolites and increases reducing sugars similar to starch-biosynthetis mutants. Heavy isotope-labelling experiments indicates that carbon flux into starch is altered in pgd3 mutants. Labelling experiments with a loss of cytosolic 6PGDH did not affect flux into starch. These results support the known role for plastid-localized oxPPP in oil synthesis and argue that amyloplast-localized oxPPP reactions are integral to endosperm starch accumulation in maize kernels.
authors.affiliation: Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Gertraud
authors.initials: G
authors.lastname: Spielbauer
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Lilla
authors.initials: L
authors.lastname: Römisch-Margl
authors.forename: Phuc Thi
authors.initials: PT
authors.lastname: Do
authors.forename: Romain
authors.initials: R
authors.lastname: Fouquet
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Eisenreich
authors.forename: Alfons
authors.initials: A
authors.lastname: Gierl
authors.forename: A Mark
authors.initials: AM
authors.lastname: Settles
mesh_terms: D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism*; D056625:Endosperm / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism* / Q000502:physiology; D013213:Starch / Q000096:biosynthesis*; D003313:Zea mays / Q000201:enzymology / Q000378:metabolism*
chemical_list: D013213:Starch; D010734:Phosphogluconate Dehydrogenase
keywords: Defective kernel; PGD3; endosperm; maize; pentose phosphate pathway; starch.