Starch Synthetase, Phosphorylase, ADPglucose Pyrophosphorylase, and UDPglucose Pyrophosphorylase in Developing Maize Kernels

Ozbun, J. L.; Hawker, J. S.; Greenberg, Elaine; Lammel, Claudia J.; Preiss, Jack; Lee, E. Y. C.

doi:10.1104/pp.51.1.1

Cited by 109 publications

(49 citation statements)

References 17 publications

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“…In growing tissues, sugars accumulate into vacuoles (9) and contribute to osmotic water potential, thus facilitating water flow into expanding cells (1). We observed that apical kernels had substantially lower sucrose concentrations and slightly higher glucose concentrations than basal kernels during the cell expansion stage (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Similar differences in the sucrose concentration of endosperm from apical and middle-position kernels have been reported recently for field-grown maize (23).…”

Section: Materiails and Methodsmentioning

confidence: 81%

“…4). Ozbun et al (11) reported that the ADPG-PPase and starch synthase activities in normal genotypes of maize endosperm were 4 to 8 and 2 to 8 times greater, respectively, than the rate of starch synthesis during the period of rapid starch accumulation. Although ADPG-PPase from maize endosperm is relatively insensitive to regulation by D-glycerate-3-P and Pi (4,26), it is possible that the current assays underestimated its potential activity due to incomplete extraction, presence of inhibitors (7), incomplete activation, or other factors.…”

Section: Materiails and Methodsmentioning

confidence: 99%

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Enzyme Activities of Starch and Sucrose Pathways and Growth of Apical and Basal Maize Kernels

Ou-Lee¹,

Setter²

1985

Plant Physiol.

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Apical kernels of maize (Zea mays L.) ears have smaller size and lower growth rates than basal kernels. To improve our understanding of this difference, the developmental patterns of starch-synthesis-pathway enzyme activities and accumulation of sugars and starch was determined in apical-and basal-kernel endosperm of greenhouse-grown maize (cultivar Cornell 175) plants. Plants were synchronously pollinated, kernels were sampled from apical and basal ear positions throughout kernel development, and enzyme activities were measured in crude preparations. Several factors were correlated with the higher dry matter accumulation rate and larger mature kernel size of basal-kernel endosperm. During the period of cell expansion (7 to 19 days after pollination), the activity of insoluble (acid) invertase and sucose concentration in endosperm of basal kernels exceeded that in apical kernels. Soluble (alkaline) invertase was also high during this stage but was the same in endosperm of basal and apical kernels, while glucose concentration was higher in apical-kernel endosperm. During the period of maximal starch synthesis, the activities of sucrose synthase, ADP-Glc-pyrophosphorylase, and insoluble (grnule-bound) ADP-Glc-starch synthase were higher in endosperm of basal than apical kernels. Soluble ADP-Glc-starch synthase, which was maximal during the early stage before starch accumulated, was the same in endosperm from apical and basal kernels. It appeared that differences in metabolic potential between apical and basal kernels were established at an early stage in kernel development.The mechanisms which control development and maintenance of kernel sink capacity in cereal grain species are not well understood. Sink capacity is determined in part by the rate of photosynthate utilization. Starch is the major constituent in mature maize kernels and thus the starch synthesis pathway could be an important site of regulation. It has been determined that starch synthesis in cereal grains involves the synthesis of ADP-Glc by ADPG-PPase2 and the incorporation of ADP-Glc into starch by ADP-Glc starch synthase (13). The invertase was suggested by radiotracer studies which indicated that sucrose was hydrolyzed in the cell wall free space prior to hexose uptake by endosperm cells (19,20).Earlier-forming kernels on a plant usually have higher survival probability (22), longer growth duration (24), and higher growth rates (21) than later forming kernels. In maize ears, the apical florets develop and pollinate several days after basal florets (24,25). The timing of pollination in maize can be controlled to synchronize all kernels on an ear, but even with this treatment apical kernels were found to have lower growth rates than did basal kernels (6). The objective of this study was to compare the activities of starch pathway enzymes in apical and basal kernels during development on synchronously pollinated ears.MATERIAILS AND METHODS Plant Material. Maize (Zea mays L., cv Cornell 175) kernels were planted on February 1, 1984 into ...

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Section: Materiails and Methodsmentioning

confidence: 81%

Section: Materiails and Methodsmentioning

confidence: 99%

Enzyme Activities of Starch and Sucrose Pathways and Growth of Apical and Basal Maize Kernels

Ou-Lee¹,

Setter²

1985

Plant Physiol.

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“…While the sequences of the maize SSIIa and SSIIb cDNAs have been published, the localization of the proteins they encode has not been defined (Imparl-Radosevich et al, 1999). Two isoforms of SS (originally designated SSI and SSII in order of elution from anion-exchange chromatography) have been described in soluble extracts of maize endosperm (Ozbun et al, 1973;Pollack and Preiss, 1980). It is now established that these isoforms are encoded by the SSI and dull1 genes, respectively (Harn et al, 1998;ImparlRadosevich et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

The Localization and Expression of the Class II Starch Synthases of Wheat1

Chu

Mouille

et al. 1999

Plant Physiology

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The starch granules of hexaploid wheat (Triticum aestivum) contain a group of three proteins known as SGP-1 (starch granule protein-1) proteins, which have apparent molecular masses of 100, 108, and 115 kD. The nature and role of these proteins has not been defined previously. We demonstrate that these polypeptides are starch synthases that are present in both the starch granule and the soluble fraction at the early stages of wheat endosperm development, but that are exclusively granule bound at mid and late endosperm development. A partial cDNA clone encoding a fragment of the 100-kD protein was obtained by screening a wheat endosperm cDNA expression library using monoclonal antibodies. Three classes of cDNA were subsequently isolated from a wheat endosperm cDNA library by nucleic acid hybridization and were shown to encode the 100-, 108-, and 115-kD proteins. The cDNA sequences are highly homologous to class II starch synthases and have the highest homology with the maize SSIIa (starch synthase IIa) gene. mRNA for the SGP-1 proteins was detected in the leaf, pre-anthesis florets, and endosperm of wheat and is highly expressed in the leaf and in the grain during the early to mid stages of development. We discuss the roles of the SGP-1 proteins in starch biosynthesis in wheat.

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“…Starch synthase activities often appear limiting to the starch accumulation rate in tissues such as maize endosperm (Ozbun et al, 1973) and pea embryo (Edwards et al, 1988;see Kruger, 1990). With regard to ADP-Glc PPase, transgenic potato tubers (Stark et al, 1992) and tomato fruit (Stark et al, 1996) with a nonallosterically controlled ADP-Glc PPase enzyme had increased starch levels, indicating that the in vivo flux through this step in biosynthesis is limiting to starch synthesis.…”

Section: Discussionmentioning

confidence: 99%

Sucrose-to-Starch Metabolism in Tomato Fruit Undergoing Transient Starch Accumulation

1997

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lmmature green tomato (Lycopersicon esculenfum) fruits undergo a period of transient starch accumulation characterized by developmental changes in the activities of key enzymes in the sucrose (Suc)-to-starch metabolic pathway. Activities of Suc synthase, fructokinase, ADP-glucose (Clc) pyrophosphorylase, and soluble and insoluble starch synthases decline dramatically in parallel to the decrease i n starch levels in the developing fruit. Comparison of "maximal" i n vitro activities of the enzymes in the Suc-to-starch pathway suggests that these same enzymes are limiting to the rate of starch accumulation. In contrast, activities of invertase, UDP-Clc pyrophosphorylase, nucleoside diphosphate kinase, phosphoglucoisomerase, and phosphoglucomutase do not exhibit dramatic decreases in activity and appear to be in excess of starch accumulation rates. Starch accumulation is spatially localized in the inner and radial pericarp and columella, whereas the outer pericarp and seed locule contain little starch. The seed locule is characterized by lower activities of Suc synthase, UDP-Clc pyrophosphorylase, phosphoglucomutase, ADP-Clc pyrophosphorylase, and soluble and insoluble starch synthases. The outer pericarp exhibits comparatively lower activities of ADP-Clc pyrophosphorylase and insoluble starch synthase only. These data are discussed in terms of the developmental and tissue-specific coordinated control of Suc-to-starch metabolism.

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Starch Synthetase, Phosphorylase, ADPglucose Pyrophosphorylase, and UDPglucose Pyrophosphorylase in Developing Maize Kernels

Cited by 109 publications

References 17 publications

Enzyme Activities of Starch and Sucrose Pathways and Growth of Apical and Basal Maize Kernels

Enzyme Activities of Starch and Sucrose Pathways and Growth of Apical and Basal Maize Kernels

The Localization and Expression of the Class II Starch Synthases of Wheat1

Sucrose-to-Starch Metabolism in Tomato Fruit Undergoing Transient Starch Accumulation

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