Multiple effects of the starch synthase II mutation in developing wheat endosperm

2007 ◽  
Vol 34 (5) ◽  
pp. 431 ◽  
Author(s):  
Behjat Kosar-Hashemi ◽  
Zhongyi Li ◽  
Oscar Larroque ◽  
Ahmed Regina ◽  
Makoto Yamamori ◽  
...  
Keyword(s):  
Triticum Aestivum L ◽  
Endosperm Development ◽  
Starch Synthase ◽  
Starch Granules ◽  
Branching Enzyme ◽  
Wild Type ◽  
Drastic Reduction ◽  
Branching Patterns ◽  
Soluble Phase ◽  
Mutant Lines

A line of wheat (Triticum aestivum L.), sgp-1, that does not express starch synthase II (SSII, also known as SGP-1) has previously been reported. In this study, F1 derived doubled haploid lines with homozygous wild type or mutant alleles for SGP-1 genes were identified from a cross between the original mutant and a wild type Australian cultivar. Analysis of the starch granules showed that in the mutant lines they are markedly distorted from 15 days postanthesis during grain development. Starch branching patterns showed an increase in the proportion of short chains (DP 6–10) at an earlier stage, but this increase became much more pronounced at 15 days postanthesis and persisted until maturity. There was also a consistent and drastic reduction throughout seed development in the relative amounts of starch branching enzyme II (SBEII, comprising SBEIIa and SBEIIb) and starch synthase I (SSI) bound to the starch granules. In the soluble phase, however, there was relatively little change in the amount of SBEIIb, SBEIIa or SSI protein. Therefore loss of SSII specifically leads to the loss of SBEIIb, SBEIIa and SSI protein in the granule-bound phase and the effect of this mutation is clearly manifest from the mid-stage of endosperm development in wheat.

Glucan affinity of starch synthase IIa determines binding of starch synthase I and starch-branching enzyme IIb to starch granules

2012 ◽  
Vol 448 (3) ◽  
pp. 373-387 ◽  
Author(s):  
Fushan Liu ◽  
Nadya Romanova ◽  
Elizabeth A. Lee ◽  
Regina Ahmed ◽  
Martin Evans ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Protein Interactions ◽  
Starch Granule ◽  
Protein Complexes ◽  
Starch Synthase ◽  
Starch Granules ◽  
Branching Enzyme ◽  
Wild Type ◽  
Protein Protein Interactions ◽  
Starch Branching Enzyme

The sugary-2 mutation in maize (Zea mays L.) is a result of the loss of catalytic activity of the endosperm-specific SS (starch synthase) IIa isoform causing major alterations to amylopectin architecture. The present study reports a biochemical and molecular analysis of an allelic variant of the sugary-2 mutation expressing a catalytically inactive form of SSIIa and sheds new light on its central role in protein–protein interactions and determination of the starch granule proteome. The mutant SSIIa revealed two amino acid substitutions, one being a highly conserved residue (Gly522→Arg) responsible for the loss of catalytic activity and the inability of the mutant SSIIa to bind to starch. Analysis of protein–protein interactions in sugary-2 amyloplasts revealed the same trimeric assembly of soluble SSI, SSIIa and SBE (starch-branching enzyme) IIb found in wild-type amyloplasts, but with greatly reduced activities of SSI and SBEIIb. Chemical cross-linking studies demonstrated that SSIIa is at the core of the complex, interacting with SSI and SBEIIb, which do not interact directly with each other. The sugary-2 mutant starch granules were devoid of amylopectin-synthesizing enzymes, despite the fact that the respective affinities of SSI and SBEIIb from sugary-2 for amylopectin were the same as observed in wild-type. The data support a model whereby granule-bound proteins involved in amylopectin synthesis are partitioned into the starch granule as a result of their association within protein complexes, and that SSIIa plays a crucial role in trafficking SSI and SBEIIb into the granule matrix.

scholarly journals Identification and molecular characterization of mutant line deficiency in three waxy proteins of common wheat (Triticum aestivum L.)

2019 ◽  
Author(s):  
Qian Liu ◽  
Yaping Hu ◽  
Mengyun Hu ◽  
Lijing Sun ◽  
Xiyong Chen ◽  
...  
Keyword(s):  
Triticum Aestivum ◽  
Amylose Content ◽  
Premature Stop Codon ◽  
Triticum Aestivum L ◽  
Starch Granules ◽  
Null Line ◽  
Wild Type ◽  
Expression Levels ◽  
Waxy Proteins ◽  
Total Starch

Abstract Background: Starch is the main component of wheat (Triticum aestivum L.) grain and a key factor in determining wheat processing quality. The Wx gene encodes the granule bound starch synthase I (GBSS I) and is the sole gene responsible for amylose synthesis. Results: A waxy mutant (Wx-null) was isolated by screening M3 seeds derived from 1.0% EMS mutagenized materials with I2-KI staining of endosperm starch. SDS-PAGE electrophoresis confirmed that the Wx-null line lacked all three waxy proteins. DNA sequencing revealed three SNPs and a 3-bp InDel in the first exon, and a 16-bp InDel at the junction region of the first Wx-A1 intron from the Wx-null line. Six SNPs were identified in Wx-B1 gene of Wx-null line compared to the wild-type Gao 8901, including four missense mutations. One nonsense mutation was found at position 857 in the fourth exon, which resulted in a premature stop codon. Expression levels of Wx genes were dramatically reduced in the Wx-null line. Nonsense-mediated mRNA decay (NMD) may be triggered to degrade the non-functional Wx mRNA. There were no detectable differences in granule size and morphology between Wx-null and wild-type, but the Wx-null line contained a larger proportion of B-type starch granules. The amylose content of the Wx-null line (0.22%) was remarkably lower compared to the wild-type Gao 8901 (20.82%). Total starch is also lower in the Wx-null line. Conclusions: All three waxy proteins were non-functional in the Wx-null line. NMD may be the cause for reduced expression levels of Wx genes in the Wx-null line. The Wx-null line exhibited more B-type starch granules, dramatically lower amylose content, and decreased total starch. The Wx-null line may provide a potential waxy material with high agronomic performance in wheat breeding programs.

scholarly journals Soluble isoforms of starch synthase and starch-branching enzyme also occur within starch granules in developing pea embryos

1993 ◽  
Vol 4 (1) ◽  
pp. 191-198 ◽  
Author(s):  
Kay Denyer ◽  
Christopher Sidebottom ◽  
Christopher M. Hylton ◽  
Alison M. Smith
Keyword(s):  
Starch Synthase ◽  
Starch Granules ◽  
Branching Enzyme ◽  
Starch Branching Enzyme

scholarly journals Characterization of wheat lacking B-type starch granules

2021 ◽  
Author(s):  
Benedetta Saccomanno ◽  
Pierre Berbezy ◽  
Kim Findlay ◽  
Jennifer Shoesmith ◽  
Cristobal Uauy ◽  
...  
Keyword(s):  
Starch Granule ◽  
Starch Content ◽  
Starch Granules ◽  
Wild Type ◽  
Bread Making ◽  
Wheat Varieties ◽  
Alcohol Production ◽  
Mutant Lines ◽  
B Granules

ABSTRACTThe physicochemical and agronomical properties of a new form of bread wheat, lacking B-type starch granules (BlessT) was assessed. Three BlessT mutant lines, made by combining homoeologous deletions of BGC1, a gene responsible for the control of B-granule content were compared with two sibling lines with normal starch phenotype and the parent line, cv. Paragon. Quantification of starch granule size and number in developing grain confirmed the lack of small, B-type starch granules throughout development in BlessT. Most starch, flour, grain and loaf characteristics did not vary between BlessT and the wild type sibling controls. However, BlessT starches had higher water absorption, reduced grain hardness and higher protein content, and dough made from BlessT flour required more water and had increased elasticity. Despite the lack of B-granules, BlessT lines do not display a significant decrease in total starch content suggesting that it should be possible to produce commercial wheat varieties that lack B-type starch granules without compromising yield. These findings support the potential utility of this novel type of wheat as a specialist crop in applications ranging from bread making and alcohol production to improved industrial starch products.

scholarly journals Granule-bound starch synthase I in isolated starch granules elongates malto-oligosaccharides processively

1999 ◽  
Vol 340 (1) ◽  
pp. 183-191 ◽  
Author(s):  
Kay DENYER ◽  
Darren WAITE ◽  
Saddik MOTAWIA ◽  
Birger Lindberg MØLLER ◽  
Alison M. SMITH
Keyword(s):  
Starch Synthase ◽  
Kinetic Properties ◽  
Starch Granules ◽  
Wild Type ◽  
Lower Affinity ◽  
Functional Differences ◽  
Glucose Molecule ◽  
Granule Bound Starch Synthase

Isoforms of starch synthase belonging to the granule-bound starch synthase I (GBSSI) class synthesize the amylose component of starch in plants. Other granule-bound isoforms of starch synthase, such as starch synthase II (SSII), are unable to synthesize amylose. The kinetic properties of GBSSI and SSII that are responsible for these functional differences have been investigated using starch granules from embryos of wild-type peas and rug5 and lam mutant peas, which contain, respectively, both GBSSI and SSII, GBSSI but not SSII and SSII but not GBSSI. We show that GBSSI in isolated granules elongates malto-oligosaccharides processively, adding more than one glucose molecule for each enzyme-glucan encounter. Granule-bound SSII can elongate malto-oligosaccharides, but has a lower affinity for these than GBSSI and does not elongate processively. As a result of these properties GBSSI synthesizes longer malto-oligosaccharides than SSII. The significance of these results with respect to the roles of GBSSI and SSII in vivo is discussed.

scholarly journals A Rubisco-binding protein is required for normal pyrenoid number and starch sheath morphology inChlamydomonas reinhardtii

2019 ◽  
Vol 116 (37) ◽  
pp. 18445-18454 ◽  
Author(s):  
Alan K. Itakura ◽  
Kher Xing Chan ◽  
Nicky Atkinson ◽  
Leif Pallesen ◽  
Lianyong Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
Structure And Function ◽  
Binding Motif ◽  
Starch Granules ◽  
Wild Type ◽  
Bisphosphate Carboxylase ◽  
Biophysical Mechanism ◽  
Mechanism Function ◽  
And Function

A phase-separated, liquid-like organelle called the pyrenoid mediates CO2fixation in the chloroplasts of nearly all eukaryotic algae. While most algae have 1 pyrenoid per chloroplast, here we describe a mutant in the model algaChlamydomonasthat has on average 10 pyrenoids per chloroplast. Characterization of the mutant leads us to propose a model where multiple pyrenoids are favored by an increase in the surface area of the starch sheath that surrounds and binds to the liquid-like pyrenoid matrix. We find that the mutant’s phenotypes are due to disruption of a gene, which we call StArch Granules Abnormal 1 (SAGA1) because starch sheath granules, or plates, in mutants lacking SAGA1 are more elongated and thinner than those of wild type. SAGA1 contains a starch binding motif, suggesting that it may directly regulate starch sheath morphology. SAGA1 localizes to multiple puncta and streaks in the pyrenoid and physically interacts with the small and large subunits of the carbon-fixing enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), a major component of the liquid-like pyrenoid matrix. Our findings suggest a biophysical mechanism by which starch sheath morphology affects pyrenoid number and CO2-concentrating mechanism function, advancing our understanding of the structure and function of this biogeochemically important organelle. More broadly, we propose that the number of phase-separated organelles can be regulated by imposing constraints on their surface area.

Characterization of cyanobacterial glycogen isolated from the wild type and from a mutant lacking of branching enzyme

2002 ◽  
Vol 337 (21-23) ◽  
pp. 2195-2203 ◽  
Author(s):  
Sang-Ho Yoo ◽  
Martin H Spalding ◽  
Jay-lin Jane
Keyword(s):  
Branching Enzyme ◽  
Wild Type
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