Normal Maize Research Articles

Rapid Birth or Death of Centromeres on Fragmented Chromosomes in Maize.

Comparative genomics has revealed common occurrences in karyotype evolution such as chromosomal end-to-end fusions and insertions of one chromosome into another near the centromere, as well as many cases of de novo centromeres that generate positional polymorphisms. However, how rearrangements such as dicentrics and acentrics persist without being destroyed or lost remains unclear. Here, we sought experimental evidence for the frequency and timeframe for inactivation and de novo formation of centromeres in maize (Zea mays). The pollen from plants with supernumerary B chromosomes was gamma-irradiated and then applied to normal maize silks of a line without B chromosomes. In ∼8,000 first-generation seedlings, we found many B-A translocations, centromere expansions, and ring chromosomes. We also found many dicentric chromosomes, but a fraction of these show only a single primary constriction, which suggests inactivation of one centromere. Chromosomal fragments were found without canonical centromere sequences, revealing de novo centromere formation over unique sequences; these were validated by immunolocalization with Thr133-phosphorylated histone H2A, a marker of active centromeres, and chromatin immunoprecipitation-sequencing with the CENH3 antibody. These results illustrate the regular occurrence of centromere birth and death after chromosomal rearrangement during a narrow window of one to potentially only a few cell cycles for the rearranged chromosomes to be recognized in this experimental regime.

The effect of pH on the chemical and structural interactions between apple polyphenol and starch derived from rice and maize.

To date, how pH affects starch–polyphenol mixtures has not been thoroughly investigated. This study explored the impact of combining apple polyphenol (AP) with both normal rice starch (NRS) and normal maize starch (NMS) across a range of pH conditions. NRS–AP mixture particle sizes across a pH range of 3–8 varied from 169.9 ± 5.4 to 187.5 ± 6.9 μm, while for NMS–AP particles, these sizes ranged from 161.8 ± 8.0 to 176.0 ± 4.9 μm, indicating that the aggregation of starch–AP was inhibited under low pH condition. The melting enthalpy (△H) values of the NRS–AP mixture across a pH range of 3–8 were 8.50 ± 0.06–9.56 ± 0.12 J/g, while the corresponding value for the NMS–AP mixture was 5.77 ± 0.05–6.21 ± 0.08 J/g. FTIR analyses revealed that the degree of order of these starch–AP mixtures significantly decreased under low pH conditions. XRD analysis further revealed that both NRS–AP and NMS–AP mixtures exhibited V‐type structures, and relative crystallinity levels decreased significantly under low pH conditions. Together, these results indicate that low pH values inhibit the recrystallization of NRS–AP and NMS–AP mixtures. Overall, these findings provide additional evidence regarding the interactions between AP and specific starches under a range of pH conditions.

Insights into the effects of caffeic acid and amylose on in vitro digestibility of maize starch-caffeic acid complex

Starch digestibility can be decreased by phenolic acids. The physicochemical and digestive properties of high-amylose maize starch, normal maize starch (NMS) and waxy maize starch (WMS) complexed with caffeic acid (CA) were investigated to determine the effects of CA and amylose on starch digestibility. CA inhibited the activity of α-glucosidase and α-amylase in a dose-dependent manner. The inhibitory effect of CA on α-glucosidase was reversible and anti-competitive, while that on α-amylase was irreversible. With the increase of the amylose content in starches, the complexing index of starch-CA decreased, while the relative crystallinity increased. The crystallinity of all three starches decreased after incorporating CA, and the hydroxyl peak in the 1H-NMR spectrum of the WMS-CA complex increased significantly. The resistant starch content of the WMS-CA and NMS-CA complexes increased significantly compared with the control. The inhibitory effect of CA on amylolytic enzymes played a major role and the change of starch structure exhibited a minor role in the digestibility of the maize starch-CA complexes.

The relationship between the expression pattern of starch biosynthesis enzymes and molecular structure of high amylose maize starch

Two high amylose (HAM) inbred lines with apparent amylose contents of 55 % and 62 %, respectively, were selected to explore the relationship between molecular structure and gene expression of starch-synthase involved enzymes. GPC analysis of debranched starches showed that the HAM starches (HAMSs) had shorter amylose chains and longer amylopectin chains than normal maize starch (NMS). FACE analysis showed that these HAMSs had a higher content of amylopectin chains of DP > 21. Quantitative Real-Time PCR analysis showed that the HAM lines had specifically low expression of the starch branching enzyme IIb (SBEIIb), and the starch synthase IIIa (SSIIIa) homologue, and high expression of the isoamylase 2 (ISA2), potentially suppressing the generation of amylopectin molecules through deficient branching and excessive debranching process, thereby increasing the relative amylose content. A high expression of GBSS1 was potentially associated with increased short amylose chain lengths in HAMSs.

Interactions in starch co-gelatinized with phenolic compound systems: Effect of complexity of phenolic compounds and amylose content of starch

Maize starches of different amylose contents were co-gelatinized with caffeic acid (CA), quercetin (Qu) and epigallocatechin gallate (EGCG), respectively. The decomposition temperature of waxy maize starch (WS)-CA blends was increased compared to WS, while that of normal maize starch (MS) and high amylose starch (HS) was decreased. The more complex of the phenolic compounds, the lower the decomposition temperature of the MS. The results of Fourier-transform infrared spectroscopy suggested that CA increased short range ordered structure of gelatinized WS but decreased that of gelatinized MS and HS. Hydrogen bonds associated with CA and starch led to the arrangement of ordered structures in different starch. Nuclear magnetic resonance (NMR) indicated that all hydroxyl groups of CA and EGCG formed hydrogen bonds, while hydroxyl group at C-4′ of quercetin had priority to form hydrogen bonds. During co-gelatinization process, more single helixes were induced in MS by CA than Qu or EGCG did.

Refinement of a protocol for the assessment of antioxidative activities of normal maize (NM) and quality protein maize (QPM)

The present investigation was performed to evaluate the effect of extraction methods (reflux and stirring) and solvent concentrations on total phenolics, flavonoids, and antioxidant activity as % inhibition, metal chelating activity, and phosphomolybdenum assay of normal maize (NM) and QPM. These compounds can be water-soluble, insoluble or bound to the cell wall and making extraction difficult. Thus, extraction plays an important role in the quantification of antioxidant activity. Results revealed that the quality protein maize (QPM) extracts possess higher flavonoids and metal chelating activity than NM, prepared using the stirring method. A significant correlation was found between phenolics and antioxidative activity for both varieties and methods. Practical applications Maize, as being an excellent source of bioactive compounds having beneficial effects on human health have great potential to reduce free radicals and protect the body from chronic diseases. Therefore, maize products can also be regarded as functional foods.

Characterization and properties of non-granular thermoplastic starch—Clay biocomposite films

Biocomposite films were prepared using as raw materials non-granular normal maize starch plasticized with glycerol and Na-montmorillonite clay particles in various concentrations. The physicochemical properties of films were studied, and their structure and morphology were investigated using XRD analysis, Thermal analysis, Scanning Electron Microscopy combined with Element Microanalysis. The mechanical characteristics were investigated through tensile test. The results indicated that the presence of clay particles in the starch matrix reduced the water absorption rate of films in comparison to starch films containing glycerol but not clay particles. The biocomposite films exhibited enhanced tensile properties at low glycerol and high clay contents. Best results were obtained for films containing 20 wt% glycerol and 10–20 wt% clay content. It is suggested that the non-granular maize starch, is a suitable raw material for the preparation of biocomposite films with improved structural and mechanical characteristics in comparison to films prepared using granular starch.

Effect of process conditions and amylose/amylopectin ratio on the pasting behavior of maize starch: A modeling approach

The effects of different process conditions on the pasting behavior of the 14%, w/w suspensions of high amylose, waxy and normal maize starches at mixing speeds of 50, 160 and 250 rpm with the heating rates of 2.5, 5 and 10 °C/min were investigated. In addition, the impact of the starch mixture with an amylose-amylopectin ratio of 0–70% at 160 rpm and a heating rate of 5 °C/min on the pasting parameters was studied. According to the results, when stirring speed decreased from 250 rpm to 50 rpm, the peak viscosity dramatically increased. Furthermore, both heating and stirring rates significantly affected the pasting properties (p < 0.05). The amylose content of maize starch had a negative correlation with peak viscosity, trough viscosity, breakdown viscosity, final viscosity, and setback viscosity. Besides, syneresis values decreased as amylose content decreased from 70% to 0%. According to the kinetic modelling of pasting curves, starch coefficients were found to be higher than 1 for all starches, indicating that the penetration of water into starch granules increased granule swelling rate. The findings of the present study confirmed that both process conditions and amylose/amylopectin ratio can be optimized without necessity of starch modification to obtain the products with the desired quality.

Learned features of leaf phenotype to monitor maize water status in the fields

Water stress significantly influences normal maize growth. Fast and effective maize water stress detection is of great help to monitor the plant status and provide scientific guidance for crop irrigation. Most of the methods are based on manual measurements of soil water content, or laboratory imaging techniques, such as hyperspectral and thermal images at plant level. With the collection of 656 original maize plant images under natural environment, a novel maize leaf image dataset with different water stress levels (well-watered, reduced-watered and drought-stressed) was constructed. This paper considers maize water status detection as a fine-grained classification problem using local leaf images. Inspired by deep learning, a convolutional neural network (CNN) is applied for the first time to maize water stress recognition. In the designed CNN architecture, feature maps from different convolutional layers are merged. Through visualization and importance analysis of the multi-scale feature maps, several specific feature maps are selected as learned features, which provide a strong discrimination ability. An SVM classifier is finally trained using the feature representation as inputs. Compared with existing techniques, the proposed method achieves the satisfying classification performance with an accuracy of 88.41%. This study also provides a quantitative measure of water stress degree using a regression model. Experimental results demonstrate that the learned features perform better than hand-crafted features to detect water stress and quantify stress severity. The proposed framework can be deployed in practical applications for a non-destructive, near real-time, and automatic monitoring of plant water status in fields.

Prospect of specialty maize as functional food to support food diversification in Indonesia

Functional maize contains various advantages over normal maize in term of usage not only since milk stage but also harvest stage. Another advantage of functional maize is the diversity of colors such as read, yellow, purple, and black with different physicochemical character. Physicochemical character of maize is the main base to choose variety that appropriate with the preferred product, by count the functional food element. Maize color is the clue of high compound content that has health benefits. For example, anthocyanin contained in purple and black maize, carotene compound in yellow and red maize, Fe mineral in red maize. Those compounds are antioxidant, mineral which needed for human health. Maize-based food products contain dietary fiber with antioxidant content hat very needed by health specially to anticipate degenerative diseases. Another challenges of specialty maize are raw materials availability and food diversification support from government. The abundant maize germplasm in Indonesia is adequate to develop, with touches of variety development and cultivation technology that can increase production will transform the special maize become functional food material that has high value. In Indonesia, MOA has released various functional maize such as QPM maize, Provit A maize, waxy maize and purple maize. This paper discussed the development of functional maize research in Indonesia and its contribution for supporting food diversity in Indonesia.

Stabilization of Pickering emulsions using starch nanocrystals treated with alkaline solution

In this work, Pickering emulsions were successfully prepared using a new Pickering stabilizer prepared from starch nanocrystals by alkaline treatment. Starch nanocrystals produced from different sources (waxy maize starch, NWS; normal maize starch, NCS) were treated with ammonia to investigate the differences in emulsifying properties of the resulting starch nanocrystals (TSNCnc, produced from NCS; TSNCwc, produced from NWS). The results of visual observation and confocal laser scanning microscopy revealed that alkaline treatment increased the Pickering-stabilizing capacity of starch nanocrystals, irrespective of starch type. The droplet size of Pickering emulsion stabilized by TSNCwc was about 5.29 μm, while droplets stabilized by TSNCnc were about 70.52 μm. The big difference between the droplet size of emulsions stabilized by TSNCnc and TSNCwc was attributed to the structural differences between the two kinds of maize starch. The droplet size of Pickering emulsion stabilized by TSNCwc was significantly smaller than that of Pickering emulsion stablilized by SNCwc. Zetasizer, transmission electron microscopy and scanning electron microscopy results showed that alkaline treatment decreased the particle size of starch nanocrystals. The present study paves the way for finding new approaches to prepare starch nanocrystals-based Pickering emulsions possessing small droplet sizes.

Conversion of a normal maize hybrid into a waxy version using in vivo CRISPR/Cas9 targeted mutation activity

Waxy maize is a specialty maize that produces mainly amylopectin starch with special food or industrial values. The objective of this study was to overcome the limitations of wx mutant allele acquisition and breeding efficiency by conversion of parental lines from normal to waxy maize. The intended mutation activity was achieved by in vivo CRISPR/Cas9 machinery involving desired-target mutation of the Wx locus in the ZC01 background, abbreviated as ZC01-DTMwx. Triple selection was applied to segregants to obtain high genome background recovery with transgene-free wx mutations. The targeted mutation was identified, yielding six types of mutations among progeny crossed with ZC01-DTMwx. The amylopectin contents of the endosperm starch in mutant lines and hybrids averaged 94.9%, while those of the wild-type controls were significantly (P < 0.01) lower, with an average of 76.9%. Double selection in transgene-free lines was applied using the Bar strip test and Cas9 PCR screening. The genome background recovery ratios of the lines were determined using genome-wide SNP data. That of lines used as male parents was as high as 98.19% and that of lines used as female parents was as high as 86.78%. Conversion hybrids and both parental lines showed agronomic performance similar to that of their wild-type counterparts. This study provides a practical example of the efficient extension of CRISPR/Cas9 targeted mutation to industrial hybrids for transformation of a recalcitrant species.

Development, structure and in vitro digestibility of type 3 resistant starch from acid-thinned and debranched pea and normal maize starches

Type 3 resistant starch (RS3) was developed from native pea starch through acid thinning, debranching and recrystallization, and the resultant pea RS3 was then characterized and compared with that generated from native normal maize starch. Starting from the respective native starches, the modification method yielded 68.1% of RS3 from pea and 59.6% from normal maize. The particles of pea and normal maize RS3 showed a coarse surface and irregular shapes and sizes. Both pea and normal maize RS3 displayed the B-type X-ray diffraction pattern, with 41.0% and 37.7% relative crystallinity, respectively. In vitro starch digestibility assay revealed that pea RS3 – in both uncooked and cooked states – was less digestible by amylolytic enzymes than normal maize RS3 because the former possessed double-helical crystallites of a more compact structure. The information presented in the study is valuable for the development of RS ingredient from pea starch for food applications.

Effects of Ligand Concentration on the Thermal Properties, Structure, and Digestibility of Maize Starch Inclusion Complexes with Ascorbyl Palmitate

AbstractThe alkaline method is used to form the complex between starch and ascorbyl palmitate (AP) in this study. Normal maize starch (NMS) and high amylose maize starch (HAMS) are screened to investigate the effects of AP concentrations (0%, 2.5%, 5.0%, 10.0%, 20.0%) on the properties of complexes at 60 °C. HAMS can bind more AP than NMS because of more amylose content. Comparing the endothermic peaks in DSC analysis, 5% and 10% AP levels are sufficient to interact with NMS and HAMS, respectively. The disappeared or weakened AP characteristic absorption peaks in FTIR spectra prove the formation of V‐amylose structure. The XRD analyses reveal that the inclusion complexes are formed with AP with six glucose units per turn due to the steric hindrance of AP, and the self‐aggregation of AP in the complexes is also detected. The self‐aggregation of AP do not affect the indigested ordered helical chain segments of starch in in vitro digestion. The 5% and 10% AP levels are enough to decrease the rate and extent of starch digestion in NMS and HAMS complexes, respectively. The formation of starch‐AP inclusion complexes also appear to enhance the stability of AP against light, heat, and oxidation.

Investigation on the Effects of Glycerol and Clay Contents on the Structure and Mechanical Properties of Maize Starch Nanocomposite Films

AbstractNanocomposite films are prepared using normal maize starch, plasticized with glycerol and water and three different types of montmorillonite clay employing the solution method. A series of samples with different compositions is prepared by varying the concentrations of glycerol and nanoclay. The tensile properties of films are investigated as a function of clay and plasticizer contents. The experimental results indicate a significant improvement in the mechanical properties of nanocomposite films prepared with sodium montmorillonite clay as compared to commercial organoclay and Kimolian montmorillonite clay. ANOVA tests and regression models indicate that both glycerol and clay contents influence significantly the mechanical properties of films, and the tensile properties of nanocomposite films are enhanced even at lower clay content. The best results are obtained with nanocomposites at glycerol concentration of about 20 wt% and clay content of about 10 wt%. The intercalated nanocomposite structure of the films is ascertained by wide angle XRD analysis whereas the morphology of samples is examined by scanning electron microscopy, optical microscopy, and confocal laser scanning microscopy.

Comparison of physicochemical properties of oca (Oxalis tuberosa), potato, and maize starches

Oca (Oxalis tuberosa) represents a novel source of starch. Starches from the tubers of two commercial oca varieties were studied for various physicochemical properties. One normal potato starch and one normal maize starch were used for comparison. Oca starches showed lower gelatinization temperatures compared to both potato and maize starches. The pasting, flow, and gelation behaviors of oca starches were intermediate between potato and maize starches. Oca starch pastes were more viscous than maize starch paste and more elastic than potato starch paste. The differences in the properties could be largely due to lower amylose content, intermediate contents of phosphate groups (~400 ppm) and granule size (34.6 μm) of oca starches as compared to the other two starches. The internal unit chains of amylopectin such as the amount of fingerprint B-chains and length of B-chains could also partially explain the different physicochemical properties among oca, potato and maize starches.

Hemijski sastav zrna genotipova kukuruza zubana, kokičara i šećerca

Maize is one of the most important field crops both in the world and in our country. All commercially grown maize hybrids can be classified into one of five elementary types: dent, flint, floury, popping and sweet maize. The objectives of this study were to characterize the grain chemical compositions of yellow-seeded and white-seeded maize dents, popping maize and sweet maize genotypes. The results show that grains contents of starch, protein, oil, crude fibre, and ash of four selected maize genotypes ranged in the intervals: 53.54-68.13%; 9.19-13.00%; 4.35-5.39%; 2.13-3.93% and 1.28-2.85%, respectively. The amylose to amylopectin ratio varied from 21:79 to 28:72, which is a principal property of normal maize starch. The content of lignocellulosic fibres: NDF, ADF, ADL, hemicellulose and cellulose ranged from 11.31-15.27%; 2.51-3.54%, 0.24-0.52%, 8.10-12.68% and 2.14-3.02%, respectively. The solubility index of albumin, globulin, zein and glutelin ranged from 9.46-29.42%, 5.64-13.13%, 21.11-28.10% and 18.81-23.69%, respectively

Improving mechanical and barrier properties of thermoplastic starch and polysaccharide nanocrystals nanocomposites

Thermoplastic starch (TPS) films were developed with normal maize starch matrix using glycerol, D-isosorbide and 1,3-propanediol as plasticizers. Besides, TPS nanocomposite films were prepared incorporating waxy starch nanocrystals (WSNC) and cellulose nanocrystals (CNC) into the normal maize starch matrix plasticized with glycerol. Both TPS films and TPS nanocomposite films were obtained by extrusion/compression method. Their mechanical and barrier properties were analyzed, as well as their viscoelastic behavior. According to the results the TPS films plasticized with D-isosorbide presented the highest transparency and the best mechanical and barrier properties, whereas 1,3-propanediol was not suitable as it was lost during the thermomechanical processing leading to brittle materials. Glycerol plasticized TPS nanocomposites were developed by incorporating polysaccharide nanocrystals, either WSNC (0, 1, 2.5 and 5 wt%) or 1 wt% of both WSNC/CNC in different proportions, in order to approximate the values to those of D-isosorbide films. The effect of both the type and the content of nanocrystal on the viscoelastic behavior and mechanical and barrier properties were investigated. The results suggested that effective interfacial hydrogen bonding interactions were achieved by extrusion/compression processing, obtaining tensile strength, strain at break and Young’s modulus increments higher than 100% for nanocomposites reinforced by only 1 wt% of polysaccharide nanocrystals, both WSNC alone and also combining WSNC/CNC in different ratios.

Parametric analysis of the spray drying process for the production of starch molecular inclusion complexes with fatty acids

Series of experimental runs were carried out using a pilot scale spray drying unit to produce starch molecular inclusion complexes with fatty acids. Native normal maize and tapioca starch suspensions with added myristic or palmitic acid were employed at various concentrations and feed rates whereas the spray drier was operated at various drying air inlet temperatures. The products were examined using X-ray diffraction analysis, scanning electron microscopy, Confocal laser scanning microscopy, differential scanning calorimetry, Laser diffraction particle size analysis. Experimental data analysis of process parameters was carried out to determine the main variables which affect the performance of the spray drying process. The critical factors were found to be the material feed flow rate in relation to the temperature difference existing in the spray drying chamber between the inlet temperature and the outlet temperature of the drying air. The results revealed that all spray dried products had the same morphological characteristics regardless the type of starch or fatty acid employed and desirable functional properties e.g., low tapped density, uniformity in size, low crystallinity and hollow porous structure. It is concluded that, spray drying is an appropriate technique for the industrial production of starch molecular inclusion complexes in powder form.

Effect of Mesona chinensis polysaccharide on the retrogradation properties of maize and waxy maize starches during storage

Waxy maize starch (WS) and normal maize starch (NS) were used to investigate the effect of Mesona chinensis polysaccharide (MCP) on the retrogradation properties of maize starch during storage. The rheological properties, water mobility, structural properties and microstructure of samples were investigated. MCP can significantly accelerate the retrogradation of WS and NS, and MCP restricted the water mobility of starch-MCP gels and diminished the decline of the spin relaxation time (T2) during retrogradation storage. In addition, the rheological and low field-nuclear magnetic resonance experiments suggested that the retrogradation of WS-MCP system mainly occurred at the later stage of retrogradation (>7 days), while retrogradation mainly took place earlier (<7days) for NS-MCP system. XRD and FT-IR results also suggested that MCP could promote the formation of more ordered structure in starch-MCP gels during storage. Moreover, SEM observation showed that MCP can better maintain the stability of gel structure during aging storage.