Showing papers on "Endosperm published in 1983"

Induction of dormancy during seed development by endogenous abscisic acid: studies on abscisic acid deficient genotypes of Arabidopsis thaliana (L.) Heynh.

Abstract: Mutant lines of Arabidopsis thaliana (L.) Heynh., which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits (siliquae) than the wild type. Reciprocal crosses of wild type and ABA-deficient mutants showed a dual origin of ABA in developing seeds. The genotype of the mother plant regulated a sharp rise in ABA content half-way seed development (maternal ABA). The genotype of the embryo and endosperm was responsible for a second ABA fraction (embryonic ABA), which reached much lower levels, but persisted for some time after the maximum in maternal ABA. The onset of dormancy correlated well with the presence of the embryonic ABA fraction and not with the maternal ABA. Dormancy developed in both the absence and presence of maternal ABA in the seeds. In this respect maternal ABA resembled exogenously applied ABA which did not induce dormancy in ABA-deficient seeds. However, both maternal and applied ABA stimulated the formation of a mucilage layer around the testa, which could be observed during imbibition of the mature seeds. In the mature state, ABA-deficient seeds germinated in the siliquae on the plant, but only when the atmosphere surrounding the plant was kept at high relative humidity. In younger stages germination in siliquae occurred after isolation from the plants and incubation on wet filter paper. Therefore, it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.

Mechanical Resistance of the Seed Coat and Endosperm during Germination of Capsicum annuum at Low Temperature

Abstract: Decoated pepper ( Capsicum annuum L. cv Early Calwonder) seeds germinated earlier at 25°C, but not at 15°C, compared to coated seeds. The seed coat did not appear to impose a mechanical restriction on pepper seed germination. Scarification of the endosperm material directly in front of the radicle reduced the time to germination at both 15°C and 25°C. The amount of mechanical resistance imposed by the endosperm on radicle emergence before germination was measured using the Instron Universal Testing Machine. Endosperm strength decreased as imbibition time increased. The puncture force decreased faster when seeds were imbibed at 25°C than at 15°C. The reduction in puncture force corresponded with the ability of pepper seeds to germinate. Most radicle emergence occurred at 15°C and 25°C after the puncture force was reduced to between 0.3 and 0.4 newtons. Application of gibberellic acid 4+7 (100 microliters per liter) resulted in earlier germination at 15°C and 25°C and decreased endosperm strength sooner than in untreated seeds. Similarly, high O 2 concentrations had similar effects on germination earliness and endosperm strength decline as did gibberellic acid 4+7 , but only at 25°C. At 15°C, high O 2 concentrations slowed germination and endosperm strength decline.

Genetic control of α-Amylase production in wheat.

Abstract: An analysis of the α-amylase isozymes in GA-treated endosperm of wheat nullisomic-tetrasomics shows that there is more variation at the α-Amy-1 and α-Amy-2 homoeoallelic loci than was previously thought Among the 16 isozymes produced by genes on the group 7 chromosomes, most could be definitely established as products of a single homoeoallele

Ricin and Ricinus communis agglutinin subunits are all derived from a single-size polypeptide precursor.

Abstract: Antibodies have been raised in rabbits against the individually purified A and B subunits of the toxic castor bean lectin, ricin, and against the A′ and B′ subunits of Ricinus communis agglutinin type I. Each of the antisera recognised a single polypeptide species of Mr 60 500 when maturing castor bean endosperm mRNA was translated in vitro in a rabbit-reticulocyte-derived system. When dog pancreatic microsomal vesicles were included in the translational system, each subunit antiserum precipitated a group of 66 000–68 000-Mr core-glycosylated polypeptides which had been translocated into the lumen of the vesicles. The 60 500-Mr polypeptide appeared to be a common precursor to all four individual lectin subunits since (a) its glycosylated (66 000 – 68 000-Mr) forms were readily detected in the endoplasmic reticulum fraction isolated from maturing castor bean endosperm and (b) pulse-chase studies showed that the glycosylated precursors disappeared from the endoplasmic reticulum fraction with the concomittant appearance of authentic lectin subunits in a soluble protein fraction which included protein body matrix components. Antiserum prepared against whole R. communis agglutinin, type I, also precipitated the 65 000-Mr precursor in vitro and in vivo, but in addition precipitated a non-glycosylated 34 000-Mr polypeptide. This smaller protein is not a lectin subunit precursor, contradicting an earlier suggestion. It is most probably a precursor to the 2-S albumin storage proteins found in castor bean endosperm protein bodies

The development of the wheat embryo in relation to the neighbouring tissues

Abstract: The overall morphology of the developing wheat embryo in relation to its neighbouring tissues is described. The embryo is “isolated” early in development, but appears to be a powerful sink for nutrients. It is supplied initially by hydrolysis of the nucellar parenchyma and later by hydrolysis of neighbouring endosperm cells, which are completely digested. Later on, the nucellar epidermis forms specialised cells that may be transfer cells opposite the groove at the base of the embryo. The accumulation of starch and protein appears to begin first in the basal tissues of the scutellum and coleorhiza.

Synthesis and processing of thionin precursors in developing endosperm from barley (Hordeum vulgare L.).

Abstract: Thionin is a lysine-rich polypeptide (mol wt 5000) which is synthesized in developing barley endosperm from ˜8 days to ˜30 days after anthesis Two thionin precursors (THP1 and THP2) have been identified using monospecific antibodies (A-TH) prepared against the mature protein THP1, which is the only polypeptide recognized in vitro by A-TH, is encoded by a 75S mRNA obtained from membrane-bound polysomes, and its alkylated derivative has an apparent mol wt of 17 800 THP2, which is selected together with mature thionin by A-TH among labelled proteins in vivo, differs from THP1 in apparent mol wt (17 400 alkylated) and in electrophoretic mobility at pH 32 Both THP1 and THP2 are competed out of the antigen-antibody complex by purified thionin The conversion of THP2 into thionin, which has been demonstrated in a pulse-chase experiment in vivo, is a post-translational process As it has not been possible to detect THP1 in vivo it is assumed that it is converted co-translationally into THP2 Final deposition of thionin as an extrinsic membrane protein, possibly associated with the endoplasmic reticulum, has been tentatively established on the basis of subcellular fractionation experiments

Endosperm cell number in cultivars of barley differing in grain weight

Abstract: SUMMARY The number of endosperm cells in caryopses 30 ‘days’ after anthesis was determined and a positive correlation was found between endosperm cell number and 1000 grain weight, and between endosperm cell number and dry grain volume in a number of cultivars of field-grown barley. The genetic factors influencing grain weight are discussed in relation to these results and to observations made on transverse sections of immature caryopses.

Oxindole-3-acetic Acid, an Indole-3-acetic Acid Catabolite in Zea mays

Abstract: A prior study (13) from this laboratory showed that oxidation of exogenously applied indole-3-acetic acid (IAA) to oxindole-3-acetic acid (OxIAA) is the major catabolic pathway for IAA in Zea mays endosperm. In this work, we demonstrate that OxIAA is a naturally occurring compound in shoot and endosperm tissue of Z. mays and that the amount of OxIAA in both shoot and endosperm tissue is approximately the same as the amount of free IAA. Oxindole-3-acetic acid has been reported to be inactive in growth promotion, and thus the rate of oxidation of IAA to OxIAA could be a determinant of IAA levels in Z. mays seedlings and could play a role in the regulation of IAA-mediated growth.

A New Mutant Gene Lowering Amylose Content in Endosperm Starch of Rice, Oryza Sativa L.

Abstract: The present study was undertaken to investigate the starch properties and inheritance of a newly induced mutant of rice. The endosperm of the mutant is dull and can be readily distinguished from the waxy as well as nonwaxy endosperms. The amylose content of the dull mutant was half as low as that of the nonwaxy counterpart. No conspicuous differences regarding the distribution of unit chain length of amylopectin existed between dull mutant and the normal counterpart. The starch properties of the dull mutant were determined three weeks after heading. Judging from the genetical analysis for amylose content of the dull mutant, it was considered that amylose production in the dull mutant is controlled by a single recessive gene which is nonallelic to the wx alleles. The amylose content did not decreased proportionally with the number of du alleles, in contrast to the proportional reduction in amylose content with the number of wx alleles. The existence of a low amylose mutant gene makes it possible to improve the eating quality of rice grains.

The Development of Enzymes During Germination and Seedling Growth in Nigerian Sorghum

Abstract: The levels of enzymes responsible for the enzymic modification of sorghum endosperm have been followed during germination and seedling growth. Sorghum β-glucanase was shown to be inactive towards barley β-glucan. Gibberellic acid does not appear to control the levels of α-amylase. In contrast to barley, the synthesis of this enzyme occurs in the embryo but it subsequently acts on the starch granules in the endosperm. Limit dextrinase, on the other hand appears to be present in the endosperm as a zymogen. Proteases were also examined during germination and seedling growth. Amino acid-releasing enzymes develop in the embryo and are absent from the endosperm, whereas endoproteases can be detected in the embryo and to a greater extent in the endosperm. Amylolytic attack on endosperm starch in sorghum is very extensive during the early stages of grain growth. The significance of these results to the malting properties of sorghum is discussed.

Genetic control of endosperm proteins in wheat : 1. The use of high resolution one-dimensional gel electrophoresis for the allocation of genes coding for endosperm protein subunits in the common wheat cultivar chinese spring.

Abstract: Total endosperm protein subunits, extracted from the common wheat cultivar Chinese Spring and from some of its aneuploid lines, were fractionated according to their molecular weight (MW) in an improved high resolution one-dimensional sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis (PAGE). The resolution obtained by this method and, in particular, that of the high molecular weight (HMW) glutenin and gliadin subunits approached that of a previous report in which two-dimensional fractionation system based on charge and MW was used. In the cultivar Chinese Spring, 21 discrete protein bands were resolved and the chromosomes controlling many of them were either reconfirmed, or, in some cases, established. The advantages of this high resolution SDS PAGE technique are discussed.

Mucronate, Mc, a dominant gene of maize which interacts with opaque-2 to suppress zein synthesis.

Abstract: This paper describes a new dominant mutation of maize, Mc, which interferes in the endosperm with the synthesis of storage proteins. The mutant is characterized by an opaque phenotype; it reduces the deposition of zein and it increases the level of methionine. The mutation is specifically related to storage protein synthesis since soluble and insoluble carbohydrates are present at normal levels. The main interest of this mutant lies in its synergistic interaction with opaque-2 in repressing zein synthesis. In the double mutant o2Mc the accumulation of zein is reduced to less than 10% of that of the normal endosperm. The control on zein synthesis exerted by the double mutant is at the level of production or stability of translatable zein mRNAs. The double mutant o2Mc germinates well offering the opportunity of using it in biochemical and molecular studies related to storage protein synthesis; the reduced endosperm weight of o2Mc negates its practical utilization in breeding maize for quality.

Genetic control of endosperm proteins in wheat. 2. Variation in high molecular weight glutenin and gliadin subunits of Triticum aestivum.

Abstract: Endosperm protein subunits of 109 primitive and modern lines of hexaploid wheat, Triticum aestivum L. em. Thell., were fractionated by one-dimensional, high resolution, sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis (PAGE). A wide range of both qualitative and quantitative variation was observed in the fractions of the high molecular weight (HMW) glutenin and gliadin subunits of the different lines. The qualitative variation was expressed in the number of subunits per fraction and in their molecular weight, as determined by the differential rate of migration. The quantitative variation was expressed in the differential staining intensity of several subunits. The widest variation was detected in the HMW glutenin and gliadin subunits controlled by chromosome 1B while a much smaller variation was observed in those subunits controlled by chromosome 1A and further smaller variation in the subunits controlled by 1D. Only a small number of subunits in both fractions was found to be controlled by chromosome 1A indicating that diploidization of endosperm protein genes in common wheat has been non-random. The genetic and evolutionary implications of these findings are discussed.

Accumulation and conversion of sugars by developing wheat grains. 3. Non‐diffusional uptake of sucrose, the substrate preferred by endosperm slices

Abstract: . Starch synthesis by developing wheat endosperm slices incubated in liquid media was more rapid, at optimum concentration, from sucrose as external substrate than from glucose and/or fructose. Fructose inhibited conversion of sucrose or glucose. The results are consistent with the hypothesis that sucrose is not hydrolysed in the apoplast before uptake. Besides a diffusional influx and efflux of labelled sucrose there was a non-diffusional influx; it was inhibited by dinitrophenol, potassium arsenate, potassium iodide, and parachloromercuribenzene sulphonate (PCMBS). PCMBS inhibited both uptake and conversion of label from 150 molm−314C-sucrose by 75%. Uptake and conversion of sucrose were stimulated by lowering pH and by fusicoccin, a promoter of proton extrusion. Extracellular solutes like raffinosc and polyethylene glycol stimulated net uptake of label from 14C-sucrose — the larger molecule being more effective — this being due to a non-specific inhibition of diffusional efflux. At too high an osmotic concentration such solutes reduced net uptake; the larger the molecule the lower this transitional concentration. In conclusion, wheat endosperm is better equipped to convert apoplastic sucrose rather than the hydrolysis products to starch; active loading of sucrose possibly involves proton co-transport; and large molecules in the extracellular solution reduce the diffusional elllux of loaded substrate.

The sorghum embryo in relation to the hydrolysis of the endosperm during germination and seedling growth

Abstract: Time-course changes in the structural and physiological properties of sorghum grain embryo have been investigated in relation to the hydrolysis of the endosperm during germination and seedling growth Histochemical analysis showed that the reserve food materials of the scutellum tissue were metabolised rapidly during germination and seedling growth Light microscope analysis of structural changes showed that scutellar epithelial cell elongation was associated with endosperm reserve mobilisation Electron microscope studies verified preliminary histochemical and light microscope findings and showed that extensive metabolism of subcellular storage materials occurred during early germination and seedling growth Physiological evidence indicated that both sorghum embryo and endosperm were insensitive to the gibberellic acid, GA3 Other hormones such as indole-3-acetic acid and kinetin also failed to induce α-amylase production This suggests that the hormonal response of the aleurone of sorghum is different from that of barley aleurone Dissection of sorghum showed that the whole body of the scutellum was capable of producing α-amylase

Expression of Storage Protein Genes in Developing Wheat (Triticum aestivum L.) Seeds : Correlation of RNA Accumulation and Protein Synthesis

Abstract: Ribonucleic acid and protein synthesis in developing wheat kernels have been studied through in vivo labeling of wheat heads in culture. In INIA 66R wheat labeled with [5-3H]uridine for 24-hour periods between 9 and 33 days after flowering, the total rate of RNA accumulation in endosperm/testa pericarp tissues was highest in the youngest seeds, and declined with increasing seed age. In contrast, the rate of accumulation of poly(A)+ RNA approximately doubled between 12 and 15 days after flowering, reached a maximum between 15 and 18 days, and declined to half the maximum rate by 24 days. Protein synthetic capacity, measured by in vitro translation of extracted seed RNA, increased in a developmental pattern similar to that of poly(A)+ RNA accumulation, but remained near maximal through 24 days after flowering. Gliadins were prominent in the in vitro translation products. When seed protein was labeled in vivo with l-[3H]leucine, extracted, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a significant change in the protein synthesis profile was apparent between 12 and 15 days after flowering, and was coincident with a marked increase in storage protein synthesis. Qualitatively similar characteristics were exhibited by the cultivar Cheyenne, although in a shorter developmental period. These results are consistent with a direct relation between levels of mRNA and rates of protein synthesis in developing wheat seeds, with a relatively long storage protein mRNA lifetime, and with control of storage protein gene expression primarily at the level of mRNA transcription.

The Incorporation of Glycolytic Intermediates into Lipids by Plastids Isolated from the Developing Endosperm of Castor Oil Seeds (Ricinus communis L.)

Abstract: Plastids were isolated from the developing endosperm of Ricinus communis L. and purified by rate-zonal centrifugation on discontinuous sucrose gradients. Assay conditions were optimized for the uptake and incorporation of 14C-acetate into lipids by intact plastids. Using the optimized conditions, the uptake and incorporation of several 14C-glycolytic intermediates into lipids were examined. Neither sucrose nor glucose-6-phosphate was incorporated into lipids. In order of increasing magnitude of incorporation, glucose, fructose, 3-phosphoglycerate, acetate, and pyruvate were metabolized to chloroform-methanol (2:1 v/v) soluble products. Pyridoxal-5'-phosphate inhibited the incorporation of 3-phosphoglycerate into lipids whereas a-cyano-4 hydroxycinnamate was without effect on pyruvate incorporation. Avidin and cerulenin did not inhibit the incorporation of acetate into lipids by intact plastids.

Superoxide dismutase in barley

Abstract: Superoxide dismutese occurs in barley where it can be measured using a xanthine oxidase assay, but not using an assay based on the reduction of Nitro Blue Tetrazolium by photo-reduced riboflavin. Three isozymes are present in the grain: two are cyanide-sensitive and one, of lower activity, is not. Superoxide dismutase is mainly in the embryo of barley and develops in the acrospire, rootlets and endosperm during germination. Synthesis of this enzyme is accelerated by exogenous gibberellic acid. Significant quantities of superoxide dismutase survive kilning: lager malts contain ca 50% more than do ale malts. The enzyme is rapidly destroyed during mashing at 65°C, but large amounts survive mashing at 45°C.

Processing aqueous treated cereals

Abstract: A process for treating cereal grains and particularly oats, to separate the endosperm from the remainder of the kernel without dry milling. The grains are soaked in an aqueous medium having a pH of 3.0 - 7.0 at a temperature in the range 40-70 °C for sufficient time to absorb at least an equal weight of the liquid medium. The condidions are such that the endosperm portion of the grain liquefies, as opposed to softens. The grain may be crushed in a variety of ways to split the husk and release the liquid endosperm contents which are then dispersed in water. The endosperm solids can be recovered from dispersion, following a screening step to separate the husks by drying to yield a substantially white, lower fiber whole endosperm flour product. Alternatively, the dispersion may be sedimented and/ or centrifuged to produce a wet solids fraction and a soluble fraction, each-of which can be subsequently recovered in dry form.

Morphology of the Crease Region in Relation to Assimilate Uptake and Water Loss During Caryopsis Development in Barley and Wheat

Abstract: Changes take place about 35 'days' after anthesis in the wall structure of the chalazal cells in caryopses of barley cv. Midas and wheat cv. Sicco grown in conditions where the number of 'days' from anthesis to harvest-ripeness is 60. The primary wall becomes lignified and is separated from the symplast by a layer of suberin. Massive deposits of electron-lucent wall material are laid down between the primary wall and the plasma membrane. From 15 'days' after anthesis increasing amounts of phenolic substances are found in the chalazal cell contents. Xylem parenchyma cells in the crease have some of the characteristics of gland cells and it is suggested that they may function in the control of the water content of the endospem. The cell wall modifications in the chalaza are interpreted as providing a means whereby, during the later stages of grain-filling, water loss from the endosperm can take place without interrupting the supply of assimilates to starchy endospem cells.

Selection and characterization of low β-glucan mutants from barley

Abstract: Four barley lines have been selected from 40,000 M2 plants derived from sodium azide-treated seeds of the high β-glucan cultivar Minerva, on the basis of low viscosity of acid extracts of flour. Two lines show a minor decrease in total β-glucan content, and two lines are low in total β-glucan, exhibit rapid endosperms modification and display a mealy endosperm. The thickness of the endosperm cell walls in the low β-glucan mutants is 3.0–3.5 μm compared with 6.5 μm for the parent variety Minerva. One of the low β-glucan mutants, has increased β-glucanase activity which might partly explain the increased rate of its modification during malting. The other mutant, M-737, has approximately the same amount of β-glucanase as Minerva and appears to be a genuine low β-glucan mutant. Malting studies confirmed the important role of endosperm cell walls as a barrier for enzyme dissemination.