Sucrose Synthase Controls Both Intracellular ADP Glucose Levels and Transitory Starch Biosynthesis in Source Leaves
Open Access
- 1 August 2005
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant and Cell Physiology
- Vol. 46 (8), 1366-1376
- https://doi.org/10.1093/pcp/pci148
Abstract
The prevailing model on transitory starch biosynthesis in source leaves assumes that the plastidial ADPglucose (ADPG) pyrophosphorylase (AGP) is the sole enzyme catalyzing the synthesis of the starch precursor molecule, ADPG. However, recent investigations have shown that ADPG linked to starch biosynthesis accumulates outside the chloroplast, presumably in the cytosol. This finding is consistent with the occurrence of an ‘alternative’ gluconeogenic pathway wherein sucrose synthase (SuSy) is involved in the production of ADPG in the cytosol, whereas both plastidial phosphoglucomutase (pPGM) and AGP play a prime role in the scavenging of starch breakdown products. To test this hypothesis, we have compared the ADPG content in both Arabidopsis and potato wild-type (WT) leaves with those of the starch-deficient mutants with reduced pPGM and AGP. These analyses provided evidence against the ‘classical’ model of starch biosynthesis, since ADPG levels in all the starch-deficient lines were normal compared with WT plants. Whether or not SuSy is involved in the synthesis of ADPG accumulating in leaves was tested by characterizing both SuSy-overexpressing and SuSy-antisensed transgenic leaves. Importantly, SuSy-overexpressing leaves exhibited a large increase of both ADPG and starch levels compared with WT leaves, whereas SuSy-antisensed leaves accumulated low amounts of both ADPG and starch. These findings show that (i) ADPG produced by SuSy is linked to starch biosynthesis; (ii) SuSy exerts a strong control on the starch biosynthetic process; and (iii) SuSy, but not AGP, controls the production of ADPG accumulating in source leaves.Keywords
This publication has 68 references indexed in Scilit:
- Most of ADP·glucose linked to starch biosynthesis occurs outside the chloroplast in source leavesProceedings of the National Academy of Sciences of the United States of America, 2004
- The Different Large Subunit Isoforms of Arabidopsis thaliana ADP-glucose Pyrophosphorylase Confer Distinct Kinetic and Regulatory Properties to the Heterotetrameric EnzymePublished by Elsevier BV ,2003
- Sucrose Synthase Catalyzes the de novo Production of ADPglucose Linked to Starch Biosynthesis in Heterotrophic Tissues of PlantsPlant and Cell Physiology, 2003
- Rice SPK, a Calmodulin-Like Domain Protein Kinase, Is Required for Storage Product Accumulation during Seed DevelopmentPlant Cell, 2002
- Reappraisal of the Currently Prevailing Model of Starch Biosynthesis in Photosynthetic Tissues: A Proposal Involving the Cytosolic Production of ADP-Glucose by Sucrose Synthase and Occurrence of Cyclic Turnover of Starch in the ChloroplastPlant and Cell Physiology, 2001
- Competitive inhibition of spinach leaf phosphoglucose isomerase isoenzymes by erythrose 4-phosphatePlant Science, 1997
- The MutT Proteins or “Nudix” Hydrolases, a Family of Versatile, Widely Distributed, “Housecleaning” EnzymesPublished by Elsevier BV ,1996
- Alteration of the Amount of the Chloroplast Phosphate Translocator in Transgenic Tobacco Affects the Distribution of Assimilate between Starch and SugarPlant Physiology, 1994
- Alterations in Growth, Photosynthesis, and Respiration in a Starchless Mutant of Arabidopsis thaliana (L.) Deficient in Chloroplast Phosphoglucomutase ActivityPlant Physiology, 1985
- Free energy changes and metabolic regulation in steady-state photosynthetic carbon reductionBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1969