Soluble Starch Synthase Enzymes in Cereals: An Updated Review

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.

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Roles of Waxy and Soluble Starch Synthase Iia Alleles in Determining Different Type Resistant Starch Contents of Rice

10.21203/rs.3.rs-107470/v1 ◽

2020 ◽

Author(s):

Hui You ◽

Ouling Zhang ◽

Xu Liang ◽

Cheng Liang ◽

Yongjun Chen ◽

...

Keyword(s):

Resistant Starch ◽

Large Diameter ◽

Starch Synthesis ◽

Soluble Starch ◽

Starch Synthase ◽

Starch Granules ◽

Milled Rice ◽

Cooked Rice ◽

Different Types ◽

Functional Starch

Abstract BackgroundResistant Starch (RS) is a functional starch that has functions of regulating diabetes, hypertension and obesity. The effects of most starch synthesis-related genes (SSRGs) on RS content and their relationships are largely unknown. ResultsIn current study, ninety-nine lines from a recombinant inbred line were selected to investigate the effects of SSRGs on the RS content in different process status. Results revealed that RS content decreased dramatically after cooking, but it did not increase significantly after cooling for 7 days. And RS was closely related to many indexes of physicochemical properties, but was not correlated with granule size. Waxy (Wx) played an important role in controlling RS content and Wxa could elevate RS content in raw milled rice, cooked rice and retrograded rice. Soluble starch synthase IIa (SSIIa) had an impact on RS2, and RS2 content of indica SSIIa were significantly higher than that of japonica SSIIa (SSIIaj). Moreover, interaction of Wx and SSIIa was responsible for variations of RS content in three sample types, RS2 and volume proportion of different size starch granules. ConclusionsWx and SSIIa together significantly regulate different types content of RS in rice, but SSIIa only affects RS2. Wxa-SSIIaj is favorable to forming large-diameter starch granules.

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QTL-seq identifies cooked grain elongation QTLs near soluble starch synthase and starch branching enzymes in rice (Oryza sativa L.)

Scientific Reports ◽

10.1038/s41598-019-44856-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 5

Author(s):

Siwaret Arikit ◽

Samart Wanchana ◽

Srisawat Khanthong ◽

Chatree Saensuk ◽

Tripop Thianthavon ◽

...

Keyword(s):

Oryza Sativa ◽

Oryza Sativa L ◽

Soluble Starch ◽

Starch Synthase ◽

Starch Branching Enzymes ◽

Branching Enzymes

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

PLANT PHYSIOLOGY ◽

10.1104/pp.105.060319 ◽

2005 ◽

Vol 138 (2) ◽

pp. 663-674 ◽

Cited By ~ 83

Author(s):

Xiaoli Zhang ◽

Alan M. Myers ◽

Martha G. James

Keyword(s):

Starch Synthesis ◽

Starch Synthase ◽

Starch Structure

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

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1613721113 ◽

2016 ◽

Vol 113 (39) ◽

pp. 10842-10847 ◽

Cited By ~ 59

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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Expression ofE. coliglycogen branching enzyme in anArabidopsismutant devoid of endogenous starch branching enzymes induces the synthesis of starch-like polyglucans

10.1101/019976 ◽

2015 ◽

Author(s):

Laura Boyer ◽

Xavier Roussel ◽

Adeline Courseaux ◽

Ofilia Mvundza Ndjindji ◽

Christine Lancelon-Pin ◽

...

Keyword(s):

Double Mutant ◽

Starch Synthesis ◽

Water Soluble ◽

Relative Importance ◽

Branching Enzyme ◽

Limited Impact ◽

Debranching Enzymes ◽

Branching Enzymes ◽

Plant Storage ◽

Glycogen Branching Enzyme

Starch synthesis requires several enzymatic activities including branching enzymes (BEs) responsible for the formation of α(1→6) linkages. Distribution and number of these linkages are further controlled by debranching enzymes (DBEs) that cleave some of them, rendering the polyglucan water-insoluble and semi-crystalline. Although the activity of BEs and DBEs is mandatory to sustain normal starch synthesis, the relative importance of each in the establishment of the plant storage polyglucan (i.e. water-insolubility, crystallinity, presence of amylose) is still debated. Here, we have substituted the activity of BEs inArabidopsiswith that of theEscherichia coliglycogen branching enzyme (GlgB). The latter is the BE counterpart in the metabolism of glycogen, a highly branched water-soluble and amorphous storage polyglucan. GlgB was expressed in thebe2 be3double mutant ofArabidopsisthat is devoid of BE activity and consequently free of starch. The synthesis of a water-insoluble, partly crystalline, amylose-containing starch-like polyglucan was restored in GlgB-expressing plants, suggesting that BEs origin only have a limited impact on establishing essential characteristics of starch. Moreover, the balance between branching and debranching is crucial for the synthesis of starch, as an excess of branching activity results in the formation of highly branched, water-soluble, poorly crystalline polyglucan.

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The Effect of High Temperature on Starch Synthesis and the Activity of Starch Synthase

Functional Plant Biology ◽

10.1071/pp9940783 ◽

1994 ◽

Vol 21 (6) ◽

pp. 783 ◽

Cited By ~ 33

Author(s):

K Denyer ◽

CM Hylton ◽

AM Smith

Keyword(s):

High Temperature ◽

Starch Content ◽

Starch Synthesis ◽

Soluble Starch ◽

Maximum Activity ◽

Starch Synthase ◽

Heat Inactivation ◽

Heat Sensitivity ◽

Potato Tubers ◽

Storage Organs

The decrease in yield which is observed when developing storage organs such as cereal grains or potato tubers are exposed to high temperatures is due to a lower final starch content. The rate of starch synthesis during the development of these storage organs at high temperature, is either reduced or fails to increase sufficiently to compensate for the shorter developmental period. This effect on the rate of starch synthesis does not seem to be due to a reduction in the supply of photosynthate. One of the enzymes in the pathway of starch synthesis, soluble starch synthase, is susceptible to heat inactivation at unusually low temperatures and may also have a low optimum temperature for maximum activity. In some storage organs, the maximum catalytic activity of soluble starch synthase is not very much greater than the rate of starch synthesis. A decrease in the activity of this enzyme is therefore, likely to affect the rate of starch synthesis. Thus, the effect of high temperature on the rate of starch synthesis may be due, at least in part, to the properties of this enzyme. This review discusses the unusual heat-sensitivity of starch synthase in the context ofthe effects of high temperature on starch synthesis in storage organs.

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Effect of biochar on rice starch properties and starch-related gene expression and enzyme activities

Scientific Reports ◽

10.1038/s41598-020-73888-2 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Diankai Gong ◽

Ximing Xu ◽

Li’an Wu ◽

Guijin Dai ◽

Wenjing Zheng ◽

...

Keyword(s):

Soluble Starch ◽

Taste Quality ◽

Starch Synthase ◽

Rice Starch ◽

Rice Varieties ◽

Starch Properties ◽

Genes Encoding ◽

Branching Enzymes ◽

Starch Debranching Enzyme

Abstract We determined the effects of biochar on starch properties and the activities of enzymes and expression levels of genes related to starch in two Japonica rice cultivars. The two rice varieties were subjected to five biochar treatments (0, control; and 5, 10, 20, and 40 t/hm2). In both rice varieties, the content of apparent amylose and resistant starch were lower in biochar treatments than in the control. The proportion of fa chains was higher and that of fb3 chain was lower in the biochar treatments than in the control. Starch viscosity and cooking taste quality were improved by the biochar treatments. In both rice varieties, the activity of granule-bound starch synthase was significantly decreased by biochar treatments, and the activities of soluble starch synthase, starch branching enzyme, and starch debranching enzyme were significantly increased. The transcript levels of genes encoding starch synthases and starch branching enzymes were significantly increased by biochar treatments. We conclude that biochar at a dose of 5–10 t/hm2 can regulate the activity of starch-related enzymes, and this affects the type, content, and fine structure of starch. Therefore, the addition of biochar to soil can improve the viscosity and taste quality of rice starch.

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Effects of high temperature on grain growth and on the metabolites and enzymes in the starch-synthesis pathway in the grains of two wheat cultivars differing in their responses to temperature

Functional Plant Biology ◽

10.1071/fp02205 ◽

2003 ◽

Vol 30 (3) ◽

pp. 291 ◽

Cited By ~ 10

Author(s):

Morteza Zahedi ◽

Rajinder Sharma ◽

Colin F. Jenner

Keyword(s):

High Temperature ◽

Starch Synthesis ◽

Grain Filling ◽

Triticum Aestivum L ◽

Soluble Starch ◽

Starch Synthase ◽

Effect Of Temperature ◽

The Difference

The effects of a sustained period of moderately high temperature were evaluated on the availability of substrate and the activity of starch synthase (ADP-glucose: 1,4-α-D-glucan 4-α-D-glucosyltransferase, EC 2.4.1.21) in the developing grains of two wheat Triticum aestivum L. cultivars differing in their tolerance to high temperature. Final grain weight was reduced by 33% in the least sensitive (cv. Kavko) and by 40% in the most sensitive (cv. Lyallpur) cultivar as post-anthesis temperature was raised from 20/15°C (day/night) to 30/25°C. The difference in the response of the two cultivars was mainly due to changes in the rate of grain filling at high temperature. The response of the rate of grain filling at high temperature, and the differential effects on the two cultivars, did not seem to be explained by an effect of temperature on the supply of assimilate (sucrose) or on the availability of the substrate for starch synthesis (ADP-glucose) in the grains. In vitro, but not in vivo, the differential responses of the efficiency (Vmax/Km) of soluble starch synthase in the two cultivars to an increase in temperature were associated with differences in the temperature sensitivity of grain filling. In vivo, the most remarkable difference between the two varieties was in the absolute values of the efficiency of soluble starch synthase, with the most tolerant cultivar having the highest efficiency.

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High Temperature Affects the Activity of Enzymes in the Committed Pathway of Starch Synthesis in Developing Wheat Endosperm

Functional Plant Biology ◽

10.1071/pp9930197 ◽

1993 ◽

Vol 20 (2) ◽

pp. 197 ◽

Cited By ~ 63

Author(s):

JS Hawker ◽

CF Jenner

Keyword(s):

High Temperature ◽

Sucrose Synthase ◽

Starch Synthesis ◽

Dry Weight ◽

Grain Filling ◽

Soluble Starch ◽

Starch Synthase ◽

Adpglucose Pyrophosphorylase ◽

Udpglucose Pyrophosphorylase ◽

Lower Temperature

Ears of wheat were exposed for up to 10 days during the grain-filling stage to high temperature (35�C) and activities of five enzymes in the sucrose to starch pathway were compared to those in ears maintained at lower temperature (21�C day/16�C night). Two cultivars of wheat known to differ in their post-anthesis tolerance of high temperature were compared. On a per grain basis, the activity of sucrose synthase and of ADPglucose pyrophosphorylase in ears maintained at 21/16�C throughout did not change greatly between days 16 and 32 after anthesis, whereas UDPglucose pyrophosphorylase and soluble starch synthase activities declined with advancing development. Soluble starch synthase activity in grains of heated ears was decreased within 1 day to about one- half of the value in unheated grains, and 3 days' additional heating did not reduce the activity much further. Insoluble starch synthase activity was not significantly reduced by heating. Compared to soluble starch synthase, ADPglucose pyrophosphorylase activity was more slowly affected and decreased to a lesser extent by heat. Sucrose synthase and UDPglucose pyrophosphorylase activities were either not affected or only slightly reduced; part of this reduction could be due to advanced development at the higher temperature. In recovery experiments ears were heated for brief periods and then returned to 21/16�C for a few days. ADPglucose pyrophosphorylase and soluble starch synthase activities recovered in the cooler conditions but the other two enzymes generally only maintained or lost further activity. From a comparison of the activities of these enzymes with the rate of starch deposition, and by taking into account the effects of heating, it is proposed that the influence of heating on final grain dry weight is attributable to the observed reductions of soluble starch synthase activity.

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