scholarly journals Properties of Citrate-stimulated Starch Synthesis Catalyzed by Starch Synthase I of Developing Maize Kernels

1979 ◽  
Vol 64 (6) ◽  
pp. 1039-1042 ◽  
Author(s):  
Charles D. Boyer ◽  
Jack Preiss
Keyword(s):  
Starch Synthesis ◽  
Starch Synthase ◽  
Maize Kernels

Starch Accumulation and Enzyme Activities Associated with Starch Synthesis in Maize Kernels

2007 ◽  
Vol 6 (7) ◽  
pp. 808-815 ◽  
Author(s):  
Hai-yan ZHANG ◽  
Shu-ting DONG ◽  
Rong-qi GAO ◽  
Qing-quan SUN
Keyword(s):  
Enzyme Activities ◽  
Starch Synthesis ◽  
Starch Accumulation ◽  
Maize Kernels

scholarly journals Triple null mutations in starch synthase SSIIa gene homoeologs lead to high amylose and resistant starch in hexaploid wheat

2020 ◽  
Author(s):  
Adam Schoen ◽  
Anupama Joshi ◽  
Vijay K Tiwari ◽  
Bikram S. Gill ◽  
Nidhi Rawat
Keyword(s):  
Resistant Starch ◽  
Amylose Content ◽  
Starch Content ◽  
Wheat Variety ◽  
Starch Synthesis ◽  
Starch Synthase ◽  
Single Individual ◽  
Individual Genome ◽  
Mutant Genotype ◽  
Knock Out

Abstract Background: Lack of nutritionally appropriate foods is one of the leading causes of obesity in the US and worldwide. Wheat (Triticum aestivum) provides 20% of the calories consumed daily across the globe. The nutrients in the wheat grain come primarily from the starch composed of amylose and amylopectin. Resistant starch content, which is known to have significant human health benefits, can be increased by modifying starch synthesis pathways. Starch synthase enzyme SSIIa, also known as starch granule protein isoform-1 (SGP-1), is integral to the biosynthesis of the branched and readily digestible glucose polymer amylopectin. The goal of this work was to develop a triple null mutant genotype for SSIIa locus in the elite hard red winter wheat variety ‘Jagger’ and evaluate the effect of the knock-out mutations on resistant starch content in grains with respect to wild type. Results: Knock-out mutations in SSIIa in the three genomes of wheat variety ‘Jagger’ were identified using TILLING. Subsequently, these loss-of function mutations on A, B, and D genomes were combined by crossing to generate a triple knockout mutant genotype Jag-ssiia-∆ABD. The Jag-ssiia-∆ABD had an amylose content of 35.70% compared to 31.15% in Jagger, leading to ~118% increase in resistant starch in the Jag-ssiia-∆ABD genotype of Jagger wheat. The single individual genome mutations also had various effects on starch composition. Conclusions: Our full null Jag-ssiia-∆ABD mutant showed a significant increase in RS without the shriveled grain phenotype seen in other ssiia knockouts in elite wheat cultivars. Moreover, this study shows the potential for developing nutritionally improved foods in a non-GM approach. Since all the mutants have been developed in an elite wheat cultivar, their adoption in production and supply will be feasible in future.

Heat Stress During Grain Filling in Maize: Effects on Carbohydrate Storage and Metabolism

1994 ◽  
Vol 21 (6) ◽  
pp. 829 ◽  
Author(s):  
GW Singletary ◽  
R Banisadr ◽  
PL Keeling
Keyword(s):  
Heat Stress ◽  
Seed Size ◽  
Starch Synthesis ◽  
Dry Weight ◽  
Grain Filling ◽  
Soluble Starch ◽  
Effect Of Temperature ◽  
Starch Accumulation ◽  
Maize Kernels

Heat stress during maize seed development can interfere with endosperm starch biosynthesis and reduce seed size, an important component of yield. Our objectives were to evaluate the direct influence of temperature during grain filling on kernel growth, carbohydrate accumulation, and corresponding endosperm metabolism. Kernels of maize were grown in vitro at 25�C until 15 or 16 days after pollination and then subjected to various temperatures for the remainder of their development. Mature kernel dry weight declined 45% in a linear fashion between 22 and 36�C. The rate of starch accumulation reached a maximum at approximately 32�C, and when measured at frequent intervals, declined only slightly with further temperature increase to 35�C. Reduced seed size resulted from an abbreviated duration of starch-related metabolism, which did not appear to be limited by endogenous sugars. Instead, a survey of 12 enzymes of sugar and starch metabolism indicated that ADP glucose pyrophosphorylase and soluble starch synthase were unique in displaying developmental peaks of activity which were compressed both in amount and time, similar to the effect of temperature on starch accumulation. We conclude that decreased starch synthesis in heat-stressed maize kernels results from a premature decline in the activity of these enzymes.

Effects of Elevated Temperature and Reduced Water Uptake on Enzymes of Starch Synthesis in Developing Wheat Grains

1990 ◽  
Vol 17 (4) ◽  
pp. 431 ◽  
Author(s):  
CY Caley ◽  
CM Duffus ◽  
B Jeffcoat
Keyword(s):  
Elevated Temperatures ◽  
Starch Content ◽  
Starch Synthesis ◽  
Dry Weight ◽  
Endosperm Development ◽  
Starch Synthase ◽  
Temperature Regimes ◽  
Endosperm Starch ◽  
Rate Limiting ◽  
Reduced Water

The mechanism of temperature regulation of endosperm development has been investigated by studying the effects of two temperature regimes on starch deposition and starch synthase activity during grain development in two cultivars of wheat. Most of the starch synthase activity was present throughout development as the granule-bound form using ADPglucose as the principal substrate. That starch synthase may be a rate-limiting enzyme for accumulation of starch, and hence dry weight, is suggested by: (1) rates are proportionately less in the cultivar with the lower final endosperm dry weight; (2) at elevated temperatures when starch content and dry weight are reduced, starch synthase activity falls; (3) the rate of starch deposition calculated to be possible from measured rates of starch synthase activity is close to the observed rate of starch deposition. On the other hand, it was concluded that it is not lack of starch synthase activity that causes termination of starch deposition, since activity is maintained well after starch deposition has ceased. Using the same two wheat cultivars, grown as detached ears in liquid culture, the effects of reduced endosperm water content, induced by the presence of polyethylene glycol in the culture medium, were investigated. Endosperm starch synthase activity was unaffected but ADPglucose pyrophosphorylase activity was greatly reduced, suggesting a possible role in the termination of starch synthesis.

Salt Tolerance and Regulation of Enzymes of Starch Synthesis in Cassava (Manihot esculenta Crantz)

1982 ◽  
Vol 9 (5) ◽  
pp. 509 ◽  
Author(s):  
JS Hawker ◽  
GM Smith
Keyword(s):  
Manihot Esculenta ◽  
Starch Synthesis ◽  
Starch Synthase ◽  
Manihot Esculenta Crantz ◽  
Adpglucose Pyrophosphorylase ◽  
Storage Organs ◽  
Porous Growth ◽  
Phosphoglyceric Acid ◽  
And Storage ◽  
Nutrient Solutions

The growth rate of cassava plants (Manihot esculenta cv. MAUS7) decreased with increasing concentrations of NaCl from 0 to 75 mM in nutrient solutions supplied regularly in a porous growth medium in a glasshouse. Tuber weight was reduced to one-half between 30 and 50 mM NaCl and there was some burning of apical leaves at 50 and 75 mM NaCl. By comparison with other plants, this cultivar of cassava can be considered to have medium sensitivity to salinity. Na+ and Cl- concentrations increased in all tissues with increasing concentrations of supplied NaCl, except that Na+ remained low in laminae until the 75 mM treatment. K+ levels decreased in tubers. Starch concentrations remained the same in tubers, and K+ stimulated starch bound ADPglucose starch synthase by 1 .5-fold. Leaves and tubers contained activities of ADPglucose pyrophosphorylase and ADPglucose-starch synthase similar to those found in leaves and storage organs of other starch synthesizing plants. ADPglucose pyrophosphorylase from leaves was stimulated 20-fold by 3-phosphoglyceric acid (3PGA) while the enzyme from tubers was almost completely dependent on 3PGA at pH 8.5. The A0.5 values for 3PGA (the concentration required for one-half maximal activation) for the leaf and tuber enzymes at pH 8.5 were 1.31 mM and 7.41 mM respectively. At pH 7.5 the leaf enzyme was stimulated 26-fold and the tuber enzyme was again almost completely dependent on 3PGA. The A0.5 values at pH 7.5 were 1.17 mM and 3.8 mM, respectively. The I0.5 values for PI (concentrations required to cause 50% inhibition) in the presence of 3PGA were 2 mM, 0.25 mM and 0.04 mM for leaf enzyme at pH 8.5 and tuber enzyme at pH 8.5 and 7.7 respectively. The results support the view that it is not possible to generalize about the magnitude of the control of ADPglucose synthesis in leaves as opposed to non-chlorophyllous tissues.

scholarly journals Structure & acceptor recognition of CLG1_GBSS, a cyanobacterial starch synthase.

2014 ◽  
Vol 70 (a1) ◽  
pp. C1167-C1167
Author(s):  
Jose Cuesta-Seijo ◽  
Morten Nielsen ◽  
Monica Palcic
Keyword(s):  
Starch Granule ◽  
Glycogen Synthase ◽  
Starch Synthesis ◽  
Caloric Intake ◽  
Starch Synthase ◽  
Complex Structures ◽  
Asymmetric Unit ◽  
Group V ◽  
The World ◽  
Shed Light

Starch synthesis was thought to occur exclusively in archaeplastida, which include green algae and land plants. Recently, amylopectin-like polymers have been identified in group V cyanobacteria[1]. In particular, a newly isolated cyanobacterium, CLG1, synthetizes granules containing both amylose and amylopectin essentially identical to plant starch[2]. These cyanobacteria are believed to have contributed some of the key starch synthesizing enzymes to plants. Starch synthases are the enzymes responsible for elongation of the maltooligosaccharide chains that compose the starch granule, working in concert with many other enzymes to create the complex structures of amylopectin and amylose. Here we report the crystal structure, refined to 2.2 Å, of GBSS, the granule bound starch synthase responsible for amylose synthesis in CLG1, in complex with ADP and either acarbose or glucose in the acceptor binding site. The structure reveals different conformational states of the ternary complex in three copies of GBSS in the asymmetric unit. The variations between monomers shed light on changes on the protein upon substrate recognition. In particular it clarifies the effect of acceptor binding in the conformation of the active site. This structure also illustrates the conformation of parts of the primary sequence that were absent from all plant starch synthase structures to date. Features in this structure are compared to both glycogen synthase and starch synthase structures. Both the similarities and the differences advance our knowledge on the necessary components of a starch synthase and point the way to their targeted structural and functional modification. The world-wide demand of cereals is expected to double from its current values by 2050 (FAO). Modification of proteins involved in starch synthesis, be it via traditional breeding or via genetic engineering, will likely be crucial to meeting the caloric intake needs of the human population in the coming decades.

scholarly journals Triple null mutations in starch synthase SSIIa gene homoeologs lead to high amylose and resistant starch in hexaploid wheat

2021 ◽  
Author(s):  
Adam Schoen ◽  
Anupama Joshi ◽  
Vijay K Tiwari ◽  
Bikram S. Gill ◽  
Nidhi Rawat
Keyword(s):  
Resistant Starch ◽  
Amylose Content ◽  
Starch Content ◽  
Wheat Variety ◽  
Starch Synthesis ◽  
Starch Synthase ◽  
Single Individual ◽  
Individual Genome ◽  
Mutant Genotype ◽  
Knock Out

Abstract Background: Lack of nutritionally appropriate foods is one of the leading causes of obesity in the US and worldwide. Wheat (Triticum aestivum) provides 20% of the calories consumed daily across the globe. The nutrients in the wheat grain come primarily from the starch composed of amylose and amylopectin. Resistant starch content, which is known to have significant human health benefits, can be increased by modifying starch synthesis pathways. Starch synthase enzyme SSIIa, also known as starch granule protein isoform-1 (SGP-1), is integral to the biosynthesis of the branched and readily digestible glucose polymer amylopectin. The goal of this work was to develop a triple null mutant genotype for SSIIa locus in the elite hard red winter wheat variety ‘Jagger’ and evaluate the effect of the knock-out mutations on resistant starch content in grains with respect to wild type. Results: Knock-out mutations in SSIIa in the three genomes of wheat variety ‘Jagger’ were identified using TILLING. Subsequently, these loss-of function mutations on A, B, and D genomes were combined by crossing to generate a triple knockout mutant genotype Jag-ssiia-∆ABD. The Jag-ssiia-∆ABD had an amylose content of 35.70% compared to 31.15% in Jagger, leading to ~118% increase in resistant starch in the Jag-ssiia-∆ABD genotype of Jagger wheat. The single individual genome mutations also had various effects on starch composition. Conclusions: Our full null Jag-ssiia-∆ABD mutant showed a significant increase in RS without the shriveled grain phenotype seen in other ssiia knockouts in elite wheat cultivars. Moreover, this study shows the potential for developing nutritionally improved foods in a non-GM approach. Since all the mutants have been developed in an elite wheat cultivar, their adoption in production and supply will be feasible in future.

scholarly journals Maize endosperm-specific transcription factors O2 and PBF network the regulation of protein and starch synthesis

2016 ◽  
Vol 113 (39) ◽  
pp. 10842-10847 ◽  
Author(s):  
Zhiyong Zhang ◽  
Xixi Zheng ◽  
Jun Yang ◽  
Joachim Messing ◽  
Yongrui Wu
Keyword(s):  
Transcription Factors ◽  
Double Mutant ◽  
Starch Content ◽  
Starch Synthesis ◽  
Starch Synthase ◽  
Maize Endosperm ◽  
Protein Levels ◽  
Pyruvate Orthophosphate Dikinase ◽  
Branching Enzymes ◽  
Critical Components

The maize endosperm-specific transcription factors opaque2 (O2) and prolamine-box binding factor (PBF) regulate storage protein zein genes. We show that they also control starch synthesis. The starch content in the PbfRNAi and o2 mutants was reduced by ∼5% and 11%, respectively, compared with normal genotypes. In the double-mutant PbfRNAi;o2, starch was decreased by 25%. Transcriptome analysis reveals that >1,000 genes were affected in each of the two mutants and in the double mutant; these genes were mainly enriched in sugar and protein metabolism. Pyruvate orthophosphate dikinase 1 and 2 (PPDKs) and starch synthase III (SSIII) are critical components in the starch biosynthetic enzyme complex. The expression of PPDK1, PPDK2, and SSIII and their protein levels are further reduced in the double mutants as compared with the single mutants. When the promoters of these genes were analyzed, we found a prolamine box and an O2 box that can be additively transactivated by PBF and O2. Starch synthase IIa (SSIIa, encoding another starch synthase for amylopectin) and starch branching enzyme 1 (SBEI, encoding one of the two main starch branching enzymes) are not directly regulated by PBF and O2, but their protein levels are significantly decreased in the o2 mutant and are further decreased in the double mutant, indicating that o2 and PbfRNAi may affect the levels of some other transcription factor(s) or mRNA regulatory factor(s) that in turn would affect the transcript and protein levels of SSIIa and SBEI. These findings show that three important traits—nutritional quality, calories, and yield—are linked through the same transcription factors.

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