Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
26,369
result(s) for
"Starch"
Sort by:
101 Kids activities that are the ooey, gooey-est ever! : nonstop fun with DIY slimes, doughs and moldables
\"Let your creativity and your imagination soar with these colorful, crazy-fun recipes for slime, dough, clay, foam, mud and more. Create amazing concoctions like Fake Snow, Color-Changing Slime and Glow-in-the-Dark Dough. Dig your fingers into Glowing Magic Mud, Shaving Cream Dough and Kool-Aid Foam. Or, if you're brave enough, squeeze the Spider Egg Sack Slime or the Frog's Vomit Slime--eek! There are even some special slimes that you can eat like Gummy Worm Slime, Pudding Slime and Cookie Dough Dough. With 101 super cool activities (that are also super easy to clean up), you can try them all! From the bestselling authors of 101 Kids Activities, 101 Coolest Simple Science Experiments and Adorkable Bubble Bath Crafts, this book is full of exciting and fantastical recipes that include tips on the science behind the goo, so you can learn too! Whether it's a slime, a dough or some other moldable creation, you'll be able to create and become whatever your imagination dreams up!\"-- Publisher's description.
Book
Inactivation of rice starch branching enzyme IIb triggers broad and unexpected changes in metabolism by transcriptional reprogramming
Starch properties can be modified by mutating genes responsible for the synthesis of amylose and amylopectin in the endosperm. However, little is known about the effects of such targeted modifications on the overall starch biosynthesis pathway and broader metabolism. Here we investigated the effects of mutating the OsSBEIIb gene encoding starch branching enzyme IIb, which is required for amylopectin synthesis in the endosperm. As anticipated, homozygous mutant plants, in which OsSBEIIb was completely inactivated by abolishing the catalytic center and C-terminal regulatory domain, produced opaque seeds with depleted starch reserves. Amylose content in the mutant increased from 19.6 to 27.4% and resistant starch (RS) content increased from 0.2 to 17.2%. Many genes encoding isoforms of AGPase, soluble starch synthase, and other starch branching enzymeswere up-regulated, either in their native tissues or in an ectopic manner, whereas genes encoding granule-bound starch synthase, debranching enzymes, pullulanase, and starch phosphorylases were largely down-regulated. There was a general increase in the accumulation of sugars, fatty acids, amino acids, and phytosterols in the mutant endosperm, suggesting that intermediates in the starch biosynthesis pathway increased flux through spillover pathways causing a profound impact on the accumulation of multiple primary and secondary metabolites. Our results provide insights into the broader implications of perturbing starch metabolism in rice endosperm and its impact on the whole plant, which will make it easier to predict the effect of metabolic engineering in cereals for nutritional improvement or the production of valuable metabolites.
Journal Article
Suppression of starch synthase I expression affects the granule morphology and granule size and fine structure of starch in wheat endosperm
Studies in Arabidopsis and rice suggest that manipulation of starch synthase I (SSI) expression in wheat may lead to the production of wheat grains with novel starch structure and properties. This work describes the suppression of SSI expression in wheat grains using RNAi technology, which leads to a low level of enzymatic activity for SSI in the developing endosperm, and a low abundance of SSI protein inside the starch granules of mature grains. The amylopectin fraction of starch from the SSI suppressed lines showed an increased frequency of very short chains (degree of polymerization, dp 6 and 7), a lower proportion of short chains (dp 8–12), and more intermediate chains (dp 13–20) than in the grain from their negative segregant lines. In the most severely affected line, amylose content was significantly increased, the morphology of starch granules was changed, and the proportion of B starch granules was significantly reduced. The change of the fine structure of the starch in the SSI-RNAi suppression lines alters the gelatinization temperature, swelling power, and viscosity of the starch. This work demonstrates that the roles of SSI in the determination of starch structure and properties are similar among different cereals and Arabidopsis.
Journal Article
PII1
The initiation of starch granule formation is still poorly understood. However, the soluble starch synthase 4 (SS4) appears to be a major component of this process since it is required to synthesize the correct number of starch granules in the chloroplasts of Arabidopsis thaliana plants.
A yeast two-hybrid screen allowed the identification of several putative SS4 interacting partners. We identified the product of At4g32190 locus as a chloroplast-targeted PROTEIN INVOLVED IN STARCH INITIATION (named PII1).
Arabidopsis mutants devoid of PII1 display an alteration of the starch initiation process and accumulate, on average, one starch granule per plastid instead of the five to seven granules found in plastids of wild-type plants. These granules are larger than in wild-type, and they remain flat and lenticular. pii1 mutants display wild-type growth rates and accumulate standard starch amounts. Moreover, starch characteristics, such as amylopectin chain length distribution, remain unchanged.
Our results reveal the involvement of PII1 in the starch priming process in Arabidopsis leaves through interaction with SS4.
Journal Article
Allelic variants of the amylose extender mutation of maize demonstrate phenotypic variation in starch structure resulting from modified protein-protein interactions
amylose extender (ae−
) starches characteristically have modified starch granule morphology resulting from amylopectin with reduced branch frequency and longer glucan chains in clusters, caused by the loss of activity of the major starch branching enzyme (SBE), which in maize endosperm is SBEIIb. A recent study with ae−
maize lacking the SBEIIb protein (termed ae1.1 herein) showed that novel protein-protein interactions between enzymes of starch biosynthesis in the amyloplast could explain the starch phenotype of the ae1.1 mutant. The present study examined an allelic variant of the ae−
mutation, ae1.2, which expresses a catalytically inactive form of SBEIIb. The catalytically inactive SBEIIb in ae1.2 lacks a 28 amino acid peptide (Val272-Pro299) and is unable to bind to amylopectin. Analysis of starch from ae1.2 revealed altered granule morphology and physicochemical characteristics distinct from those of the ae1.1 mutant as well as the wild-type, including altered apparent amylose content and gelatinization properties. Starch from ae1.2 had fewer intermediate length glucan chains (degree of polymerization 16-20) than ae1.1. Biochemical analysis of ae1.2 showed that there were differences in the organization and assembly of protein complexes of starch biosynthetic enzymes in comparison with ae1.1 (and wild-type) amyloplasts, which were also reflected in the composition of starch granule-bound proteins. The formation of stromal protein complexes in the wild-type and ae1.2 was strongly enhanced by ATP, and broken by phosphatase treatment, indicating a role for protein phosphorylation in their assembly. Labelling experiments with [γ-32P]ATP showed that the inactive form of SBEIIb in ae1.2 was phosphorylated, both in the monomeric form and in association with starch synthase isoforms. Although the inactive SBEIIb was unable to bind starch directly, it was strongly associated with the starch granule, reinforcing the conclusion that its presence in the granules is a result of physical association with other enzymes of starch synthesis. In addition, an Mn2+-based affinity ligand, specific for phosphoproteins, was used to show that the granule-bound forms of SBEIIb in the wild-type and ae1.2 were phosphorylated, as was the granule-bound form of SBEI found in ae1.2 starch. The data strongly support the hypothesis that the complement of heteromeric complexes of proteins involved in amylopectin synthesis contributes to the fine structure and architecture of the starch granule.
Journal Article
Starch synthases SSIIa and GBSSI control starch structure but do not determine starch granule morphology in the absence of SSIIIa and SSIVb
Key message
High levels of two major starch synthases, SSIIa and GBSSI, in
ss3a ss4b
double mutant rice alter the starch structure but fail to recover the polygonal starch granule morphology.
The endosperm starch granule is polygonal in wild-type rice but spherical in double mutant
japonica
rice lacking genes encoding two of the five major Starch synthase (SS) isozymes expressed in endosperm, SSIIIa and SSIVb.
Japonica
rice naturally has low levels of SSIIa and Granule-bound SSI (GBSSI). Therefore, introduction of active
SSIIa
allele and/or high-expressing
GBSSI
allele from
indica
rice into the
japonica
rice mutant lacking SS isozymes can help elucidate the compensatory roles of SS isozymes in starch biosynthesis. In this study, we crossed the
ss3a ss4a
double mutant
japonica
rice with the
indica
rice to generate three new rice lines with high and/or low SSIIa and GBSSI levels, and examined their starch structure, physicochemical properties, and levels of other starch biosynthetic enzymes. Lines with high SSIIa levels showed more SSI and SSIIa bound to starch granule, reduced levels of short amylopectin chains (7 ≤ DP ≤ 12), increased levels of amylopectin chains with DP > 13, and consequently higher gelatinization temperature. Lines with high GBSSI levels showed an increase in amylose content. The ADP-glucose content of the crude extract was high in lines with low or high SSIIa and low GBSSI levels, but was low in lines with high GBSSI. Addition of high SSIIa and GBSSI altered the starch structure and physicochemical properties but did not affect the starch granule morphology, confirming that SSIIIa and SSIVb are key enzymes affecting starch granule morphology in rice. The relationship among SS isozymes and its effect on the amount of substrate (ADP-glucose) is discussed.
Journal Article
Starch as a source, starch as a sink
Starch commands a central role in the carbon budget of the majority of plants on earth, and its biological role changes during development and in response to the environment. Throughout the life of a plant, starch plays a dual role in carbon allocation, acting as both a source, releasing carbon reserves in leaves for growth and development, and as a sink, either as a dedicated starch store in its own right (in seeds and tubers), or as a temporary reserve of carbon contributing to sink strength, in organs such as flowers, fruits, and developing non-starchy seeds. The presence of starch in tissues and organs thus has a profound impact on the physiology of the growing plant as its synthesis and degradation governs the availability of free sugars, which in turn control various growth and developmental processes. This review attempts to summarize the large body of information currently available on starch metabolism and its relationship to wider aspects of carbon metabolism and plant nutrition. It highlights gaps in our knowledge and points to research areas that show promise for bioengineering and manipulation of starch metabolism in order to achieve more desirable phenotypes such as increased yield or plant biomass.
Journal Article
Phosphorylation of transitory starch by α‐glucan, water dikinase during starch turnover affects the surface properties and morphology of starch granules
Glucan, water dikinase (GWD) is a key enzyme of starch metabolism but the physico‐chemical properties of starches isolated from GWD‐deficient plants and their implications for starch metabolism have so far not been described. Transgenic Arabidopsis thaliana plants with reduced or no GWD activity were used to investigate the properties of starch granules. In addition, using various in vitro assays, the action of recombinant GWD, β‐amylase, isoamylase and starch synthase 1 on the surface of native starch granules was analysed. The internal structure of granules isolated from GWD mutant plants is unaffected, as thermal stability, allomorph, chain length distribution and density of starch granules were similar to wild‐type. However, short glucan chain residues located at the granule surface dominate in starches of transgenic plants and impede GWD activity. A similarly reduced rate of phosphorylation by GWD was also observed in potato tuber starch fractions that differ in the proportion of accessible glucan chain residues at the granule surface. A model is proposed to explain the characteristic morphology of starch granules observed in GWD transgenic plants. The model postulates that the occupancy rate of single glucan chains at the granule surface limits accessibility to starch‐related enzymes.
Journal Article
Deficiency of Starch Synthase IIIa and IVb Alters Starch Granule Morphology from Polyhedral to Spherical in Rice Endosperm
Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production.
Journal Article
Recent developments in understanding the regulation of starch metabolism in higher plants
This article reviews current knowledge of starch metabolism in higher plants, and focuses on the control and regulation of the biosynthetic and degradative pathways. The major elements comprising the synthetic and degradative pathways in plastids are discussed, and show that, despite present knowledge of the core reactions within each pathway, understanding of how these individual reactions are co-ordinated within different plastid types and under different environmental conditions, is far from complete. In particular, recently discovered aspects of the fine control of starch metabolism are discussed, which indicate that a number of key reactions are controlled by post-translational modifications of enzymes, including redox modulation and protein phosphorylation. In some cases, enzymes of the pathway may form protein complexes with specific functional significance. It is suggested that some of the newly discovered aspects of fine control of the biosynthetic pathway may well apply to many other proteins which are directly and indirectly involved in polymer synthesis and degradation.
Journal Article