scholarly journals Mutations Affecting Starch Synthase III in Arabidopsis Alter Leaf Starch Structure and Increase the Rate of Starch Synthesis

2005 ◽  
Vol 138 (2) ◽  
pp. 663-674 ◽  
Author(s):  
Xiaoli Zhang ◽  
Alan M. Myers ◽  
Martha G. James
Keyword(s):  
Starch Synthesis ◽  
Starch Synthase ◽  
Starch Structure

scholarly journals Soluble Starch Synthase Enzymes in Cereals: An Updated Review

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1983
Author(s):  
Ahsan Irshad ◽  
Huijun Guo ◽  
Shoaib Ur Rehman ◽  
Xueqing Wang ◽  
Chaojie Wang ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
Starch Synthesis ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Cereal Crops ◽  
Starch Granules ◽  
Starch Structure ◽  
Debranching Enzymes ◽  
Branching Enzymes ◽  
Starch Yield

Cereal crops have starch in their endosperm, which has provided calories to humans and livestock since the dawn of civilization to the present day. Starch is one of the important biological factors which is contributing to the yield of cereal crops. Starch is synthesized by different enzymes, but starch structure and amount are mainly determined by the activities of starch synthase enzymes (SS) with the involvement of starch branching enzymes (SBEs) and debranching enzymes (DBEs). Six classes of SSs are found in Arabidopsis and are designated as soluble SSI-V, and non-soluble granule bound starch synthase (GBSS). Soluble SSs are important for starch yield considering their role in starch biosynthesis in cereal crops, and the activities of these enzymes determine the structure of starch and the physical properties of starch granules. One of the unique characteristics of starch structure is elongated glucan chains within amylopectin, which is by SSs through interactions with other starch biosynthetic enzymes (SBEs and DBEs). Additionally, soluble SSs also have conserved domains with phosphorylation sites that may be involved in regulating starch metabolism and formation of heteromeric SS complexes. This review presents an overview of soluble SSs in cereal crops and includes their functional and structural characteristics in relation to starch synthesis.

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.

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 Genetic Control and High Temperature Effects on Starch Biosynthesis and Grain Quality in Rice

2021 ◽  
Vol 12 ◽  
Author(s):  
Hua Zhang ◽  
Heng Xu ◽  
Yingying Jiang ◽  
Heng Zhang ◽  
Shiyu Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Molecular Mechanisms ◽  
Grain Quality ◽  
Amylose Content ◽  
Starch Synthesis ◽  
Grain Filling ◽  
Eating Quality ◽  
Starch Structure ◽  
Long Time ◽  
Cooking And Eating Quality

Grain quality is one of the key targets to be improved for rice breeders and covers cooking, eating, nutritional, appearance, milling, and sensory properties. Cooking and eating quality are mostly of concern to consumers and mainly determined by starch structure and composition. Although many starch synthesis enzymes have been identified and starch synthesis system has been established for a long time, novel functions of some starch synthesis genes have continually been found, and many important regulatory factors for seed development and grain quality control have recently been identified. Here, we summarize the progress in this field as comprehensively as possible and hopefully reveal some underlying molecular mechanisms controlling eating quality in rice. The regulatory network of amylose content (AC) determination is emphasized, as AC is the most important index for rice eating quality (REQ). Moreover, the regulatory mechanism of REQ, especially AC influenced by high temperature which is concerned as a most harmful environmental factor during grain filling is highlighted in this review.

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.

scholarly journals Starch biosynthesis in developing seeds

2010 ◽  
Vol 21 (1) ◽  
pp. 5-32 ◽  
Author(s):  
Ian J. Tetlow
Keyword(s):  
Seedling Establishment ◽  
Biological Function ◽  
Starch Synthesis ◽  
Industrial Applications ◽  
Starch Biosynthesis ◽  
Post Translational Modification ◽  
Developing Seeds ◽  
Starch Structure ◽  
Wide Range ◽  
Storage Starch

AbstractStarch is globally important as a source of food and, in addition, has a wide range of industrial applications. Much of this agriculturally produced starch is synthesized in developing seeds, where its biological function is to provide energy for seedling establishment. Storage starch in developing seeds is synthesized in heterotrophic plastids called amyloplasts and is distinct from the transient synthesis of starch in chloroplasts. This article reviews our current understanding of storage starch biosynthesis occurring in these organelles and discusses recent advances in research in this field. The review discusses starch structure and granule initiation, emerging ideas on the evolution of the pathway, the enzymes of starch synthesis, and the post-translational modification and regulation of key enzymes of amylopectin biosynthesis.

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