Starch phosphorylation in potato tubers proceeds concurrently with de Novo biosynthesis of starch

The in vivo phosphorylation of starch was studied in Solanum tuberosum cv Dianella and Posmo. Small starch granules contain 25% more ester-bound phosphate per glucose residue than large starch granules. The degree of phosphorylation was found to be almost constant during tuber development. Isolated...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1994-05, Vol.105 (1), p.111-117
Main Authors: Nielsen, T.H, Wischmann, B, Enevoldsen, K, Moller, B.L
Format: Article
Language:English
Subjects:
Acid hydrolysis
Agronomy. Soil science and plant productions
ALMIDON
AMIDON
Biological and medical sciences
BIOSINTESIS
BIOSYNTHESE
Biosynthesis
CHOIX DE LA DATE
DIMENSION
ELECCION DE LA EPOCA
FISIOLOGIA POSTCOSECHA
Fluorides
FOSFORILACION
Fundamental and applied biological sciences. Psychology
Metabolism
Metabolism and Enzymology
Phosphates
Phosphorus
PHOSPHORYLATION
Photosynthesis, respiration. Anabolism, catabolism
PHYSIOLOGIE APRES RECOLTE
Plant physiology and development
Plants
Radioactive decay
SOLANUM TUBEROSUM
Starches
TUBERCULE
TUBERCULO
Tubers
VARIACION GENETICA
VARIATION GENETIQUE
VARIEDADES
VARIETE
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Description
Summary:The in vivo phosphorylation of starch was studied in Solanum tuberosum cv Dianella and Posmo. Small starch granules contain 25% more ester-bound phosphate per glucose residue than large starch granules. The degree of phosphorylation was found to be almost constant during tuber development. Isolated tuber discs synthesize starch from externally supplied glucose at a significant rate. Tuber discs supplied with glucose and [32P]orthophosphate incorporate radiolabeled phosphorus into the starch. The level of 32P incorporation is proportional to the amount of starch synthesized. The incorporation of 32P from orthophosphate is correlated to de novo synthesis of starch, since the incorporation diminished upon inhibition of starch synthesis by fluoride. Based on the amount of [14C]glucose phosphate isolated after hydrolysis of purified starch from tuber discs incubated in the presence of [U-14C]glucose, approximately 0.5% of the glucose residues of the de novo-synthesized starch are phosphorylated. This value is in general agreement with the observed levels of phosphorus in starch accumulated during tuber development. Thus, the enzyme system responsible for starch phosphorylation is fully active in the isolated tuber discs, and the starch phosphorylation proceeds as an integrated part of de novo starch synthesis
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.105.1.111