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Open Biology Jun 2021is a ubiquitous pathogen infecting one-third of the global population. A significant fraction of toxoplasmosis cases is caused by reactivation of existing chronic...
is a ubiquitous pathogen infecting one-third of the global population. A significant fraction of toxoplasmosis cases is caused by reactivation of existing chronic infections. The encysted bradyzoites during chronic infection accumulate high levels of amylopectin that is barely present in fast-replicating tachyzoites. However, the physiological significance of amylopectin is not fully understood. Here, we identified a starch synthase (SS) that is required for amylopectin synthesis in . Genetic ablation of SS abolished amylopectin production, reduced tachyzoite proliferation, and impaired the recrudescence of bradyzoites to tachyzoites. Disruption of the parasite Ca-dependent protein kinase 2 (CDPK2) was previously shown to cause massive amylopectin accumulation and bradyzoite death. Therefore, the mutant is thought to be a vaccine candidate. Notably, deleting SS in a mutant completely abolished starch accrual and restored cyst formation as well as virulence in mice. Together these results suggest that regulated amylopectin production is critical for the optimal growth, development and virulence of . Not least, our data underscore a potential drawback of the mutant as a vaccine candidate as it may regain full virulence by mutating amylopectin synthesis genes like SS.
Topics: Amylopectin; Animals; Antigens, Protozoan; Cell Line; Glucose; Humans; Mice; Mutation; Phylogeny; Protozoan Proteins; Protozoan Vaccines; Starch Synthase; Toxoplasma; Toxoplasmosis; Vaccine Development; Virulence
PubMed: 34129780
DOI: 10.1098/rsob.200384 -
International Journal of Molecular... Feb 2023Large-scale use of fossil fuels has brought about increasingly serious problems of environmental pollution, development and utilization of renewable energy is one of the...
Large-scale use of fossil fuels has brought about increasingly serious problems of environmental pollution, development and utilization of renewable energy is one of the effective solutions. Duckweed has the advantages of fast growth, high starch content and no occupation of arable land, so it is a promising starchy energy plant. A new submerged duckweed mutant () with abundant starch accumulation was obtained, whose content of amylopectin accounts for 84.04% of the starch granules. Compared with the wild type (), the branching degree of starch in mutant was significantly increased by 19.6%. Chain length DP 6-12, DP 25-36 and DP > 36 of amylopectin significantly decreased, while chain length DP 13-24 significantly increased. Average chain length of wild-type and mutant starches were greater than DP 22. Moreover, the crystal structure and physical properties of starch have changed markedly in mutant. For example, the starch crystallinity of mutant was only 8.94%, while that of wild-type was 22.3%. Compared with wild type, water solubility of starch was significantly reduced by 29.42%, whereas swelling power significantly increased by 97.07% in mutant. In order to further analyze the molecular mechanism of efficient accumulation of amylopectin in mutant, metabolome and transcriptome were performed. The results showed that glucose accumulated in mutant, then degradation of starch to glucose mainly depends on α-amylase. At night, the down-regulated β-amylase gene resulted in the inhibition of starch degradation. The starch and sucrose metabolism pathways were significantly enriched. Up-regulated expression of , , , , and provide sufficient substrate for starch synthesis in mutant. From the 0H to 16H light treatment, granule-bound starch synthase () gene was inhibited, on the contrary, the starch branching enzyme () gene was induced. Differential expression of and may be an important reason for the decrease ratio of amylose/amylopectin in mutant. Taken together, our results indicated that the mutant can accumulate the amylopectin efficiently, potentially through altering the differential expression of , and . This study also provides theoretical guidance for creating crop germplasm with high amylopectin by means of synthetic biology in the future.
Topics: Amylopectin; Starch; Amylose; 1,4-alpha-Glucan Branching Enzyme; Araceae; Starch Synthase
PubMed: 36769258
DOI: 10.3390/ijms24032934 -
Plant Science : An International... May 2022Starch is a complex carbohydrate polymer produced by plants and especially by crops in huge amounts. It consists of amylose and amylopectin, which have α-1,4- and... (Review)
Review
Starch is a complex carbohydrate polymer produced by plants and especially by crops in huge amounts. It consists of amylose and amylopectin, which have α-1,4- and α-1,6-linked glucose units. Despite this simple chemistry, the entire starch metabolism is complex, containing various (iso)enzymes/proteins. However, whose interplay is still not yet fully understood. Starch is essential for humans and animals as a source of nutrition and energy. Nowadays, starch is also commonly used in non-food industrial sectors for a variety of purposes. However, native starches do not always satisfy the needs of a wide range of (industrial) applications. This review summarizes the structural properties of starch, analytical methods for starch characterization, and in planta starch modifications.
Topics: Amylopectin; Amylose; Carbohydrate Metabolism; Plants; Starch
PubMed: 35351303
DOI: 10.1016/j.plantsci.2022.111223 -
Scientific Reports Jan 2022Waxy maize rich in amylopectin has emerged as a preferred food. However, waxy maize is poor in lysine and tryptophan, deficiency of which cause severe health problems....
Waxy maize rich in amylopectin has emerged as a preferred food. However, waxy maize is poor in lysine and tryptophan, deficiency of which cause severe health problems. So far, no waxy hybrid with high lysine and tryptophan has been developed and commercialized. Here, we combined recessive waxy1 (wx1) and opaque2 (o2) genes in the parental lines of four popular hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) using genomics-assisted breeding. The gene-based markers, wx-2507F/RG and phi057 specific for wx1 and o2, respectively were successfully used to genotype BCF, BCF and BCF populations. Background selection with > 100 SSRs resulted in recovering > 94% of the recurrent parent genome. The reconstituted hybrids showed 1.4-fold increase in amylopectin (mean: 98.84%) compared to the original hybrids (mean: 72.45%). The reconstituted hybrids also showed 14.3% and 14.6% increase in lysine (mean: 0.384%) and tryptophan (mean: 0.102%), respectively over the original hybrids (lysine: 0.336%, tryptophan: 0.089%). Reconstituted hybrids also possessed similar grain yield (mean: 6248 kg/ha) with their original versions (mean: 6111 kg/ha). The waxy hybrids with high lysine and tryptophan assume great significance in alleviating malnutrition through sustainable and cost-effective means. This is the first report of development of lysine and tryptophan rich waxy hybrids using genomics-assisted selection.
Topics: Amylopectin; Chimera; Genes, Plant; Genes, Recessive; Genomics; Genotype; Lysine; Plant Breeding; Selection, Genetic; Tryptophan; Zea mays
PubMed: 35027624
DOI: 10.1038/s41598-021-04698-3 -
Frontiers in Plant Science 2020It is known that one of starch branching enzyme (BE) isoforms, BEIIb, plays a specific role not only in the synthesis of distinct amylopectin cluster structure, but also...
It is known that one of starch branching enzyme (BE) isoforms, BEIIb, plays a specific role not only in the synthesis of distinct amylopectin cluster structure, but also in the formation of the internal structure of starch granules in rice endosperm because in its absence the starch crystalline polymorph changes to the B-type from the typical A-type found in the wild-type (WT) cereal endosperm starch granules. In the present study, to examine the contribution of BEIIb to the amylopectin cluster structure, the chain-length distributions of amylopectin and its phosphorylase-limit dextrins (Φ-LD) from endosperm and culm of a null mutant called () mutant line, EM10, were compared with those of its WT cultivar, Kinmaze, of rice. The results strongly suggest that BEIIb specifically formed new short chains whose branch points were localized in the basal part of the crystalline lamellae and presumably in the intermediate between the crystalline and amorphous lamellae of amylopectin clusters in the WT endosperm, whereas in its absence branch points which were mainly formed by BEI were only located in the amorphous lamellae of amylopectin. These differences in the cluster structure of amylopectin between Kinmaze and EM10 endosperm were considered to be responsible for the differences in the A-type and B-type crystalline structures of starch granules between Kinmaze and EM10, respectively. The changes in internal structure of starch granules caused by BEIIb were analyzed by wide angle X-ray diffraction, small-angle X-ray scattering, solid state C NMR, and optical sum frequency generation spectroscopy. It was noted that the size the amylopectin cluster in endosperm (approximately 8.24 nm) was significantly smaller than that in WT endosperm (approximately 8.81 nm). Based on the present results, we proposed a model for the cluster structure of amylopectin in WT and mutant of rice endosperm. We also hypothesized the role of BEIIa in amylopectin biosynthesis in culm where BEIIb was not expressed and instead BEIIa was the major BE component in WT of rice.
PubMed: 33312184
DOI: 10.3389/fpls.2020.571346 -
Rice (New York, N.Y.) Apr 2022Rice endosperm accumulates large amounts of photosynthetic products as insoluble starch within amyloplasts by properly arranging structured, highly branched, large... (Review)
Review
Rice endosperm accumulates large amounts of photosynthetic products as insoluble starch within amyloplasts by properly arranging structured, highly branched, large amylopectin molecules, thus avoiding osmotic imbalance. The amount and characteristics of starch directly influence the yield and quality of rice grains, which in turn influence their application and market value. Therefore, understanding how various allelic combinations of starch biosynthetic genes, with different expression levels, affect starch properties is important for the identification of targets for breeding new rice cultivars. Research over the past few decades has revealed the spatiotemporal expression patterns and allelic variants of starch biosynthetic genes, and enhanced our understanding of the specific roles and compensatory functions of individual isozymes of starch biosynthetic enzymes through biochemical analyses of purified enzymes and characterization of japonica rice mutants lacking these enzymes. Furthermore, it has been shown that starch biosynthetic enzymes can mutually and synergistically increase their activities by forming protein complexes. This review focuses on the more recent discoveries made in the last several years. Generation of single and double mutants and/or high-level expression of specific starch synthases (SSs) allowed us to better understand how the starch granule morphology is determined; how the complete absence of SSIIa affects starch structure; why the rice endosperm stores insoluble starch rather than soluble phytoglycogen; how to elevate amylose and resistant starch (RS) content to improve health benefits; and how SS isozymes mutually complement their activities. The introduction of active-type SSIIa and/or high-expression type GBSSI into ss3a ss4b, isa1, be2b, and ss3a be2b japonica rice mutants, with unique starch properties, and analyses of their starch properties are summarized in this review. High-level accumulation of RS is often accompanied by a reduction in grain yield as a trade-off. Backcrossing rice mutants with a high-yielding elite rice cultivar enabled the improvement of agricultural traits, while maintaining high RS levels. Designing starch structures for additional values, breeding and cultivating to increase yield will enable the development of a new type of rice starch that can be used in a wide variety of applications, and that can contribute to food and agricultural industries in the near future.
PubMed: 35438319
DOI: 10.1186/s12284-022-00570-8 -
Frontiers in Nutrition 2021Increasing the ratio of amylose in the diet can increase the quantity of starch that flows to the large intestine for microbial fermentation. This leads to the...
Increasing the ratio of amylose in the diet can increase the quantity of starch that flows to the large intestine for microbial fermentation. This leads to the alteration of microbiota and metabolite of the hindgut, where the underlying mechanism is not clearly understood. The present study used a combination of 16S amplicon sequencing technology and metabolomics technique to reveal the effects of increasing ratios of amylose/amylopectin on cecal mucosa- and digesta-associated microbiota and their metabolites in young goats. Twenty-seven Xiangdong black female goats with average body weights (9.00 ± 1.12 kg) were used in this study. The goats were randomly allocated to one of the three diets containing starch with 0% amylose corn (T1), 50% high amylose corn (T2), and 100% high amylose corn (T3) for 35 days. Results showed that cecal valerate concentration was higher ( < 0.05) in the T2 group than those in the T1 and T3 groups. The levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were decreased ( < 0.05) in cecal tissue while IL-10 was increased ( < 0.05) in the T2 group when compared with T1 or T3 groups. At the phylum level, the proportion of mucosa-associated Spirochaetes was increased ( < 0.05), while Proteobacteria was deceased by feeding high amylose ratios ( < 0.05). The abundance of Verrucomicrobia was decreased ( < 0.05) in the T3 group compared with the T1 and T2 groups. The abundance of digesta-associated Firmicutes was increased ( < 0.05) while Verrucomicrobia and Tenericutes were deceased ( < 0.05) with the increment of amylose/amylopectin ratios. The LEfSe analysis showed that a diet with 50% high amylose enriched the abundance of beneficial bacteria such as and in the digesta and in the mucosa compared with the T1 diet. The metabolomics results revealed that feeding a diet containing 50% high amylose decreased the concentration of fatty acyls-related metabolites, including dodecanedioic acid, heptadecanoic acid, and stearidonic acid ethyl ester compared with the T1 diet. The results suggested that a diet consisting of 50% high amylose could maintain a better cecal microbiota composition and host immune function.
PubMed: 34957184
DOI: 10.3389/fnut.2021.774766 -
Eukaryotic Cell Apr 2010There are currently intensive global research efforts aimed at increasing and modifying the accumulation of lipids, alcohols, hydrocarbons, polysaccharides, and other... (Review)
Review
There are currently intensive global research efforts aimed at increasing and modifying the accumulation of lipids, alcohols, hydrocarbons, polysaccharides, and other energy storage compounds in photosynthetic organisms, yeast, and bacteria through genetic engineering. Many improvements have been realized, including increased lipid and carbohydrate production, improved H(2) yields, and the diversion of central metabolic intermediates into fungible biofuels. Photosynthetic microorganisms are attracting considerable interest within these efforts due to their relatively high photosynthetic conversion efficiencies, diverse metabolic capabilities, superior growth rates, and ability to store or secrete energy-rich hydrocarbons. Relative to cyanobacteria, eukaryotic microalgae possess several unique metabolic attributes of relevance to biofuel production, including the accumulation of significant quantities of triacylglycerol; the synthesis of storage starch (amylopectin and amylose), which is similar to that found in higher plants; and the ability to efficiently couple photosynthetic electron transport to H(2) production. Although the application of genetic engineering to improve energy production phenotypes in eukaryotic microalgae is in its infancy, significant advances in the development of genetic manipulation tools have recently been achieved with microalgal model systems and are being used to manipulate central carbon metabolism in these organisms. It is likely that many of these advances can be extended to industrially relevant organisms. This review is focused on potential avenues of genetic engineering that may be undertaken in order to improve microalgae as a biofuel platform for the production of biohydrogen, starch-derived alcohols, diesel fuel surrogates, and/or alkanes.
Topics: Biofuels; Carbohydrate Metabolism; Eukaryota; Fatty Acids; Genetic Engineering; Genome; Hydrogen; Lipid Metabolism; Photosynthesis
PubMed: 20139239
DOI: 10.1128/EC.00364-09 -
Food Science and Biotechnology Apr 2021A combination of freeze-dried powder of disproportionating enzyme (D-enzyme)-containing potato tuber and β-amylase-containing ramie leaf was used to improve the...
A combination of freeze-dried powder of disproportionating enzyme (D-enzyme)-containing potato tuber and β-amylase-containing ramie leaf was used to improve the gluten-free (GF) bread, and its physicochemical properties were characterized. The presence of D-enzyme and β amylase in the potato tuber and ramie leaf was confirmed. Sixty five percent of partially gelatinized rice flour and 20% corn starch was combined with 10% freeze-dried potato tuber and 1% ramie leaf powder, and baked. The specific volume increased by 23% compared to the control with improved internal characteristics. Texture profile analysis revealed that retrogradation of the bread was retarded when stored for 90 h at 4 °C. The bread crumb amylose content was reduced from 14 to 9% and amylopectin branch chain-length distribution was rearranged, whereby the proportions of the branch chains with Degree of polymerization (DP) < 9 and DP > 19 decreased. The results suggest that D-enzyme and β-amylase cooperatively altered amylose/amylopectin ratio and amylopectin structure.
PubMed: 33936843
DOI: 10.1007/s10068-021-00891-2 -
Foods (Basel, Switzerland) Dec 2022This study was to investigate the impact of granule size, amylose content, and starch molecular characteristics on pasting and rheological properties of starch...
This study was to investigate the impact of granule size, amylose content, and starch molecular characteristics on pasting and rheological properties of starch paste/gels in neutral (water) and sugar-acid systems. Normal rice starch (RS), waxy rice starch (WRS), normal tapioca starch (TS), and waxy tapioca starch (WTS) representing small-granule starches and intermediate-granule starches respectively, were used in the study. Impacts of granule size, AM content, and their synergistic effects resulted in different starch susceptibility to acid hydrolysis and interactions between starch and sucrose-water, yielding different paste viscosities in both systems. The high molecular weight (Mw¯) and linearity of amylopectin and amylose molecules increased the consistency of starch pastes. RS produced a stronger and more brittle gel than other starch gels in both neutral and sugar-acid systems. The results indicated the impact of the effect of granule size and amylose content on starch gel behaviors. Properties of waxy starch gels were mainly governed by amylopectin molecular characteristics, especially in the sugar-acid system. Adding sugar and acid had minor impacts on starch gel behaviors in the linear viscoelastic (LVE) region but were most evident in the nonlinear response regime of starch gels as shown in the Lissajous curves at large oscillatory strain.
PubMed: 36553803
DOI: 10.3390/foods11244060