Acid In Maize Research Articles

Study of low‐molecular weight organic acids in maize roots under the stress of cadmium using capillary zone electrophoresis

An indirect CE method was developed for the study of low-molecular weight organic acids (LMWOAs) in maize under the stress of cadmium. The influences of indirect reagents (phthalate, salicylic acid, and benzoic acid), coion concentration, and pH were studied. A buffer composed of 15 mmol/L benzoate and 0.2 mmol/L CTAB (pH 5.7) was used in the organic acid determination. The detection limit ranged between 0.5 and 6 micromol/L. The RSD (n = 14) of the method was found to be in the range of 0.11-0.49% for migration time and 1.25-4.72% for peak area. In the maize roots, obvious increases of LMWOAs were observed when the plants were under the stress of cadmium and/or organic acids. The recovery of standard organic acids added in real samples ranged from 85 to 116%.

Endogenous losses of energy and amino acids in birds and their effect on true metabolisable energy values and availability of amino acids in maize

1. Endogenous losses of amino acids (EAAL) and energy (EEL) were determined in unfed adult cockerels. The intercepts of linear regression analysis were determined using 44 birds precision-fed on maize. During the experimental period (48 h), excreta of birds were collected, and the samples of maize and the excreta were dried, ground and assayed for gross energy and amino acids. 2. The EAAL and EEL in unfed cockerels influenced true available amino acid (TAAA) values. Therefore, the intercept of regressions showed an increase in TAAA values of maize. 3. The results indicated that there was no significant difference between the data obtained for EEL from the unfed birds and from regression analysis so, the figure from regression analysis could be used for calculating the true metabolisable energy (TME) value of maize. 4. The calculated EAAL from regression analysis caused an increase in the TAAA value in maize. The amounts of metabolic and endogenous amino acid excretions varied in voided excreta from unfed birds. These differences would be related to genetics, age, sex and environmental temperatures.

Bimodal distribution of fasting gastric acidity in a rural African population.

The people of Transkei eat a diet high in linoleic acid, the principal fatty acid in maize. The theory has been put forward that a diet high in linoleic acid and low in fat and riboflavin, such as the traditional diet in Transkei, results in overproduction of prostaglandin E2 in the gastric mucosa, and that this overproduction in turn causes a suppression of gastric acid production. To investigate the effect of diet on fasting gastric pH in a rural black African population. Fasting gastric acid samples were obtained by fine nasogastric tube aspiration from 150 volunteers at a rural health clinic. The pH of these samples was measured and a full dietary questionnaire was used. Helicobacter pylori serology was done on a subgroup of 30 volunteers. A bimodal pH distribution was found. Approximately half the population had a gastric pH within the range 1-4. Half had a pH of over 4. A high pH was significantly associated with consumption of maize (p = 0.006), and with consumption of both pumpkin and beans (p = 0.006). A high proportion of this rural African population has a diet-associated abnormally high gastric pH. The pattern of upper gastrointestinal disease may be significantly affected by diet in this community and in others with a similar diet.

The genetic basis of C-glycosyl flavone B-ring modification in maize (Zea mays L.) silks.

Resistance to corn earworm (CEW) (Helicoverpa zea Boddie) has been attributed to high concentrations of C-glycosyl flavones and chlorogenic acid in maize (Zea mays L.) silks. The most common C-glycosyl flavones isolated from maize silks are maysin, apimaysin, and methoxymaysin, which are distinguished by their B-ring substitutions. For a better understanding of the genetic mechanisms underlying the synthesis of these compounds, we conducted a quantitative trait locus (QTL) study with two populations: (Tx501 x NC7A)F2 and (Tx501 x Mp708)F2. For chlorogenic acid, maysin, and methoxymaysin concentration, the major QTL for both populations was located on chromosome 4 near umc1963. For apimaysin, the major QTL in both populations was located at the position of the pr1 locus on chromosome 5. The QTL alleles on chromosome 4 that increased the synthesis of methoxymaysin significantly decreased the synthesis of maysin and chlorogenic acid. This decrease in maysin concentration was four-fold greater than the increase in methoxymaysin. Our results indicate that the QTL on chromosome 4, responsible for the increase in methoxymaysin synthesis, alters the dynamics of both the phenylpropanoid and flavonoid pathways.

Cell wall-bound phenolics in cells of maize ( Zea mays, Gramineae) and buckwheat ( Fagopyrum tataricum, Polygonaceae) with different plant regeneration abilities

Six different tissue types were used in these studies: both regenerable and nonregenerable calli of different morphotypes of buckwheat ( Fagopyrum tataricum, Polygonaceae) and maize ( Zea mays, Gramineae) inbred Pa91 as well as two maize inbred cultures, H99-R and H99-NR, with similar compact (embryogenic-like) structure but different regeneration abilities. The lignin levels measured by the thioglycolic acid method in the lines with different regeneration abilities 3 weeks after subculture were somewhat higher in regenerable than in nonregenerable calli. The total amount of wall bound phenolic acids in buckwheat (dicotyledonous plant) was similar to that of maize (monocotyledonous plant), but the maize cell walls contained a much higher proportion of esterified phenolic acids than the buckwheat cell walls. The buckwheat had almost equal amounts of ester and ether linked phenolic acids, while the maize cell walls had 90% or more esterified linkages. Much higher amounts of hydroxycinnamic acids are bound to the cell walls of regenerable compared with the nonregenerable buckwheat and Pa91 calli; ferulic and p-coumaric acids in maize, and ferulic and sinapic acids in buckwheat. Room temperature alkaline treatment released almost all of the ether linked sinapic acid and about 75–80% of the total etherified ferulic acid from the buckwheat cell walls without breaking the ether linkages. The hydroxycinnamic acid contents were very similar in the two maize inbred H99 lines with similar morphology but different plant regeneration potential. These results indicate that wall bound phenolics, in particular ferulic acid, may be associated with a certain tissue morphological structure, that is necessary but not sufficient for plant regeneration since additional factors seem to be required for morphogenesis in vitro.

Free Amino Acids in Maize (Zea mays L.) Anthers During Microsporogenesis

The objective of this work was to identify and quantify the free amino acids in the anther of the hybrid maize H-34 and the traditional cultivar Zac.58-VO during microsporogenesis. Anthers were studied in three stages of their development: (I) differentiation, (II) mid-uninucleate meiotic stage, and (III) at anthesis of plants growing in the field. Amino acids were chemically modified with o-phthaldialdehyde and quantified by HPLC. Anthers of the traditional cv. Zac.58-VO had a low concentration of free amino acids, especially at stage I. This cultivar reached the highest amino acid concentration at stage II (2 502 nmols/100 mg of fresh tissue) with alanine, asparagine and glutamate occurring as the most abundant amino acids (70 % of the total). In contrast, the amino acid content in the anthers of the hybrid H-34 dramatically increased with anther development, from 1 278 nmols/100 mg in stage I to 5 799 in the stage III. Among the 18 amino acids identified some of the most abundant were aspartate, glutamate, asparagine and glutamine, and γ-aminobutyric acid was found only in this cultivar (H-34). In both cultivars, alanine, asparagine, aspartate, phenylalanine and valine presented high positive correlation with other amino acids. In the hybrid, another nine amino acids increased to 105 the total number of significant correlations between pairs of amino acids, in contrast with only 35 in the traditional cultivar. The results support the hypothesis that the content of amino acids in the anthers of maize varies with the stage of anther development and with the cultivar.

Level changes of jasmonic, abscisic, and indole-3yl-acetic acids in maize under desiccation stress

Desiccation-stress conditions were applied to the roots of etiolated Zea mays L. (cv. Zhengsan 3) plantlets using polyethylene glycol (PEG) solutions. Levels of JA, ABA and IAA in the roots and shoots were quantitatively determined by ELISAs at 0, 1, 3, 5, 7 and 13 h. The enhancement in JA and ABA levels in both roots and shoots during desiccation stress was observed. The largest increases in the root and shoot contents of ABA were found at 5 h (about 3.2-fold) and 7 h (about 6.3-fold), respectively. The IAA root level increased strongly after 1 h of immersion, and reached its highest value at 3 h (about 5.2-fold), then decreased. However, the level of IAA in the shoots decreased rapidly, and reached its lowest value at 7 h (about one-fourth).

Quantitative determination of some amino acids in maize seed and seaweed by micellar electrokinetic chromatography

Quantitative determination of some amino acids in maize seed and seaweed by micellar electrokinetic chromatography

Quantitative determination of some amino acids in maize seed and seaweed by micellar electrokinetic chromatography

This article presents the utilization of micellar electrokinetic chromatography for the quantitative determination of some amino acids as dansyl and didansyl derivatives of maize seed and spirulina-type seaweed. During the work, the repeatability of hydrolysis, derivatization, and analysis were evaluated. Some selected free amino acids were derivatized at different concentrations and calibration curves were prepared. The absolute content of individual amino acids was determined in a few types of maize seed flour and in one type of seaweed. To cover the entire electropherogram, amino acids from the beginning, middle, and end of the electropherogram were selected. A newly developed method was used for the determination and quantitation of the di-dansyl derivative of lysine. © 1997 John Wiley & Sons, Inc. J Micro Sep9: 451–457, 1997

Biodegradability of Free Monomeric and Cell-Wall-Bound Phenolic Acids in Maize Stover by Two Strains of White-Rot Fungi

Development of fungal bioconversion technology to upgrade feeding value of fibrous crop residues into animal feed requires the understanding of the impact of fungal treatments on cell wall phenolic acids. This study investigated the capacity of two strains of white-rot fungi, Phanerochaete chrysosporiumandPhlebia brevispora, in degrading cell wall-bound phenolic acids in maize (Zea maizeL) stover and the free phenolic monomers in a liquid culture medium. In the study, 150 mg litre−1 ofp-coumaric acid (PCA), ferulic acid (FA), syringic acid (SYA),p-hydroxybenzoic acid (PHBA), vanillic acid (VA), and 200 mg litre−1 of caffeic acid (CA) were added to a liquid nutrient medium and incubated with each of the fungi for 28 days. The results indicated that within 21 days the fungal treatments completely removed the added PCA and FA from the medium, and over 94% of SYA was degraded after 28 days. During the incubation periods, VA and PHBA were also extensively removed byP chrysosporium, but resistant to degradation byP brevispora. Disappearance of caffeic acid from the medium was related to both fungal degradation and abiotic hydrolysis. In the culture media,P chrysosporiumwas superior toP brevisporain removing the phenolic acids. Solid incubation of maize stover with the selected fungi for 28 days resulted in extensive degradation of cell-wall-bound FA and PCA. However, complete degradation of cell wall FA and PCA did not occur in maize stover. In contrast to results in pure liquid medium,P chrysosporiumdegraded only 20% of the initial concentration of cell wall PCA, and was less effective in degrading cell wall FA compared toP brevispora. These results indicate that the white-rot fungi were able to degrade phenolic acids both in pure culture medium and in cell wall matrix of maize stover. Furthermore,P brevisporaexhibited stronger ability to degrade cell-wall-bound phenolic acids. Thus, this fungus can be more effective for the enhancement of fibre digestibility.

Indole is an intermediate in the biosynthesis of cyclic hydroxamic acids in maize

Mass spectrometry, deuterium NMR and TLC radioactivity analysis of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) 8, recovered from maize shoots grown in the presence of indole-[2H6] and 2-[14C]indole show that indole is a precursor of DIMBOA.

The in vitro biosynthesis of indole-3-butyric acid in maize

The in vitro biosynthesis of indole-3-butyric acid (IBA) was investigated in maize ( Zea mays L.). Incubation of microsomal membranes from shoots and roots of dark-grown maize with labelled indole-3-acetic acid (IAA), acetyl coenzyme A (acetyl CoA) and ATP resulted in the formation of an unknown labelled reaction product, product X. Other coenzymes had very little effect on the formation of this product. No IBA was detected in this system. The labelled product was purified and fed to other cell fractions of dark-grown maize. Incubation with the organelle fraction using NADPH as a cofactor resulted in the conversion of product X to a new compound which had the retention time of IBA in HPLC. Attempts to identify product X led to the hypothesis that it is a conjugate of IAA with ADP. Microsomal membranes from light-grown shoots and roots converted IAA to IBA, as demonstrated by HPLC analysis. The identity of the IBA peak was confirmed by GC-mass spectrometry. Microsomal membranes from light-grown roots formed both IBA and little of product X. For the direct in vitro biosynthesis of IBA acetyl CoA was needed as a cofactor, and the reaction as enhanced by the addition of ATP or NADPH. The optimum pH of the in vitro formation of IBA was 6–7 in the roots and 5 in the shoots. Product X was formed only at neutral pH (7–8). The K m value for IAA in the synthesis of IBA was 16 μ m.

2H-1,4-benzoxazin-3(4H)-one, an intermediate in the biosynthesis of cyclic hydroxamic acids in maize

2H-1,4-Benzoxazin-3(4H)-one has been identified as an intermediate in the biosynthesis of cyclic hydoxamic acids in maize by showing that the deuterium labelled compound is incorporated into DIMBOA with high retention of deuterium and high efficiency, by trapping radioactivity from [ 14C] anthranilic acid in a pool of unlabelled benzoxazinone administered to maize shoots, and by showing that benzoxazinone is oxidized to DIBOA by maize microsomes in an NADPH- and oxygen-dependent reaction.

Effects of hydroxamic acids on electron transport and their cellular location in corn

DIMBOA, the main hydroxamic acid in maize and wheat, is found mainly as a glucoside in intact maize plants; when the tissue is damaged a β-glucosidase releases DIMBOA from DIMBOA-glucoside. The effects of DIMBOA and its glucoside were studied in maize mitochondria and chloroplasts. DIMBOA reduced electron transport in both mitochondria and chloroplasts with an ID 50 of 1.8 and 1.2 mM, respectively. DIMBOA-glucoside had no inhibitory effect. The glucoside and the enzyme were both present in mesophyll parenchyma protoplasts. When these protoplasts were fractionated, DIMBOA-glucoside was found in the extravacuolar fraction, while the DIMBOA-β-glucosidase was in the vacuole. This seems to be an efficient mechanism to prevent aglycone toxicity in vivo.

The Post Valve T‐Caecum cannulation technique in pigs applicated to determine the digestibility of amino acid in maize, groundnut and sunflower meal

ZusammenfassungDie Post Valve T‐Caecum Kanulierungstechnik beim Schwein zur Bestimmung der Verdaulichkeit von AminosäurenEs wird die Post Valve T‐Caecum (PVTC) Technik als Kanülierungstechnik zur Bestimmung der ilealen Verdaulichkeit beschrieben. Ein Verdaulichkeitsversuch mit PVTC‐fistulierten Schweinen wurde durchgeführt, um diese Technik anzuwenden.Die PVTC Kanüle ist direkt gegenüber der Ileocaecalklappe plaziert. Da die Kanüle in das Colon gesetzt wird, ist der Einfluß auf die Motilität des Ileums minimiert. PVTC fistulierte Schweine können über einen längeren Zeitraum genutzt werden, ohne daß Anzeichen von Unbehagen auftreten. Die Chymussammlung mit PVTC fistulierten Schweinen ist annähernd quantitativ, dennoch ist ein Marker notwendig.Es wurde ein Verdaulichkeitsexperiment mit drei in ihren Rohfasergehalten unterschiedlichen Futtermitteln durchgeführt: Mais 1,8%, Erdnußextraktionsschrot 12,7%, Sonnenblumenextraktionsschrot 23,6%. Die Ergebnisse der ilealen Verdaulichkeit, des Rohproteins und der nicht essentiellen Aminosäuren dieser drei Futtermittel wurden mit Daten der Literatur verglichen. Bei Erdnußextraktionsschrot variierten die Verdaulichkeiten zwischen den Versuchen. Bei Mais war die Anzahl der Beobachtungen begrenzt. Die in diesem Experiment und den aufgeführten Untersuchungen dargestellten Ergebnisse für die Verdaulichkeit des Rohproteins und der nicht essentiellen Aminosäuren in Sonnenblumenextraktionsschrot bestand eine gute Übereinstimmung.

Lysine-insensitive aspartate kinase in two threonine-overproducing mutants of maize

Aspartate kinase (AK; EC 2.7.2.A) catalyzes the first reaction in the biosynthesis pathway for aspartate-derived amino acids in plants. Aspartate kinase was purified from wildtype and two maize (Zea mays L.) genotypes carrying unlinked dominant mutations,Ask LT19 andAsk2 -LT20, that conferred overproduction of threonine, lysine, methionine and isoleucine. The objective of this investigation was to characterize the AKs from mutant and wildtype plants to determine their role in regulating the synthesis of aspartate-derived amino acids in maize. Kernels of the homozygousAsk2 mutant exhibited 174-, 10-, 13- and 2-fold increases in, in this sequence, free threonine, lysine, methionine and isoleucine, compared to wildtype. In wildtype maize, AK was allosterically feedback-inhibited by lysine with 10 μML-lysine required for 50% inhibition. In contrast, AK purified from the isogenic heterozygousAsk and homozygousAsk2 mutants required 25 and 760 μM lysine for 50% inhibition, respectively, indicating thatAsk andAsk2 were separate structural loci for lysine-regulated AK subunits in maize. Further characterization of purified AK from the homozygous mutantAsk2 line indicated altered substrate and lysine inhibition kinetics. The apparent Hill coefficient was 0.7 for the mutantAsk2 AK compared with 1.6 for the wildtype enzyme, indicating that the mutant allele conferred the loss of a lysinebinding site to the mutant AK. Lysine appeared to be a linear noncompetitive inhibitor ofAsk2 AK with respect to MgATP and an uncompetitive inhibitor with respect to aspartate compared to S-parabolic, I parabolic noncompetitive inhibition of wildtype AK. Reduced lysine sensitivity of theAsk2 gene product appeared to reduce the lysine inhibition of all of the AK activity detected in homozygousAsk2 plants, indicating that maize AK is a heteromeric enzyme consisting of the two lysine-sensitive polypeptides derived from theAsk andAsk2 structural genes.

Hydroxamic Acid Glucosyltransferases from Maize Seedlings

Hydroxamic acids occur in several forms in maize (Zea mays L.) with 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) being the predominant form and others including 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) being found at lower concentrations. Two enzymes capable of glucosylating hydroxamic acids were identified in maize protein extracts and partially purified and characterized. The total enzyme activity per seedling increased during the first 4 days of germination and was concurrent with the accumulation of DIMBOA. Purification of the enzymes by ammonium sulfate precipitation followed by Sephadex G-200 and Q-Sepharose gel chromatography resulted in a 13-fold increase in specific activity. The enzymes are initially separated into two peaks (peak 1 and peak 2) of activity by Q-Sepharose gel chromatography. The peak 1 glucosyltransferase had 3.6% of the DIMBOA glucosylating activity when DIBOA was used as substrate, whereas this percentage increased to 57% for the peak 2 enzyme. The enzyme in peak 2 has a K(m) of 174 micromolar for DIMBOA and a K(m) of 638 micromolar for DIBOA; the enzyme in peak 1 has a K(m) of 217 micromolar for DIMBOA and its activity on DIBOA was too low to determine a K(m). The identification of two glucosyltransferases capable of glucosylating hydroxamic acids in vitro serves as an initial step in the characterization of the enzymes involved in production of hydroxamic acids in maize.

Digestibilities of amino acids in maize, wheat and barley meals, determined with intact and caecectomised cockerels.

1. Maize, wheat and barley meals, and a protein-free diet were each force-fed to 24 intact and 24 caecectomised adult cockerels. For each test, birds were starved of solid food for 48 h, fed, and then excreta collected for 48 h. 2. Quantities of nitrogen (N) and amino acids excreted after feeding the protein-free diet did not differ between intact and caecectomised birds. 3. True digestibility coefficients of N and amino acids did not differ between intact and caecectomised birds. 4. Differences between cereals in apparent digestibility of amino acids were inconsistent and more readily attributed to differences between amino acid intake than bioavailability. 5. Differences between cereals in true digestibility of amino acids were confined to higher values for N, aspartic acid, alanine and leucine in maize than in barley or wheat meals.

Digestibility of amino acids in maize, wheat and barley meal, measured in pigs with ileo‐rectal anastomosis and isolation of the large intestine

AbstractMaize, soft wheat and barley diets were compiled to have similar crude fibre (CF) concentration by addition of purified cellulose. Protein‐free diets, with purified cellulose included at 60 g kg−1 dry matter (DM) (PF1) and 90 g kg−1 DM (PF2), were formulated. Each of four littermate, male pigs (22 kg liveweight) was surgically modified to create an ileo‐rectal anastomosis with complete isolation of the large intestine. Diets were fed, and the ileal digesta, excreted via the anus, were collected. Endogenous amino acid output was higher after feeding PF2 than PF1. The choice of factor for correction of apparent digestibility (AD) to true digestibility (TD) was based upon CF intake of cereal diet. AD of most essential amino acids was greater in wheat than in maize or barley, although AD of lysine in barley (67.1%) was higher than in maize (56.8%) or wheat (63.4%). TD of most essential amino acids was higher for wheat and maize than for barley, although TD of lysine was similar for all cereals. Lysine and threonine were the most poorly digested essential amino acids in all cereals.

Effects of water stress on the gas exchange, the activities of some enzymes of carbon and nitrogen metabolism, and on the pool sizes of some organic acids in maize leaves

Water-stressed maize (Zea mays L.) leaves showed a large decrease in leaf conductance during photosynthesis. Net CO2 uptake and evaporation declined fast at mild stress (ψ=-0.6 to -1.0 MPa) and slower at more severe stress (ψ=-1.0 to -1.2 MPa), whereas the CO2 concentration in the intercellular spaces (Ci) did not drop to the CO2 compensation point. The activities of the enzymes of photosynthetic carbon metabolism tested in this study dropped by approx. 30% at ψ=-1.2 MPa. Glutamine synthetase activity was unaffected by water stress, whereas the activity of nitrate reductase was almost completely inhibited. The decline of enzyme activities in relation to ψ was correlated with a concomitant decrease in the content of total soluble protein of the stressed leaves. The total leaf pools of malate, pyruvate and oxaloacetate decreased almost linearly in relation to ψ, thus obviously contradicting the almost constant Ci. In comparison to the controls (ψ=0.6 MPa) the content of citrate and isocitrate increaed markedly at ψ=-0.9 MPa and decreased again at ψ=-1.2 MPa.