Showing papers on "Endosperm published in 1988"
TL;DR: In this article, the relationship between amylose content and lipid content in wheat, barley, maize and rice starches is described and the biological significance of the lipids is discussed.
355 citations
TL;DR: The argument for the selective uptake of triose phosphates by the amyloplast as part of the pathway of starch biosynthesis from sucrose in plant storage tissues is seriously weakened and it is suggested that a hexose phosphate such as glucose 1-phosphate, glucose 6-ph phosphate, or fructose 6-Phosphate is the most likely candidate for entry into the ameloplast.
Abstract: We have used 13C-labeled sugars and nuclear magnetic resonance (NMR) spectrometry to study the metabolic pathway of starch biosynthesis in developing wheat grain (Triticum aestivum cv Mardler). Our aim was to examine the extent of redistribution of 13C between carbons atoms 1 and 6 of [1-13C] or [6-13C]glucose (or fructose) incorporated into starch, and hence provide evidence for or against the involvement of triose phosphates in the metabolic pathway. Starch synthesis in the endosperm tissue was studied in two experimental systems. First, the 13C sugars were supplied to isolated endosperm tissue incubated in vitro, and second the 13C sugars were supplied in vivo to the intact plant. The 13C starch produced by the endosperm tissue of the grain was isolated and enzymically degraded to glucose using amyloglucosidase, and the distribution of 13C in all glucosyl carbons was quantified by 13C-NMR spectrometry. In all of the experiments, irrespective of the incubation time or incubation conditions, there was a similar pattern of partial (between 15 and 20%) redistribution of label between carbons 1 and 6 of glucose recovered from starch. There was no detectable increase over background 13C incidence in carbons 2 to 5. Within each experiment, the same pattern of partial redistribution of label was found in the glucosyl and fructosyl moieties of sucrose extracted from the tissue. Since it is unlikely that sucrose is present in the amyloplast, we suggest that the observed redistribution of label occurred in the cytosolic compartment of the endosperm cells and that both sucrose and starch are synthesized from a common pool of intermediates, such as hexose phosphate. We suggest that redistribution of label occurs via a cytosolic pathway cycle involving conversion of hexose phosphate to triose phosphate, interconversion of triose phosphate by triose phosphate isomerase, and resynthesis of hexose phosphate in the cytosol. A further round of triose phosphate interconversion in the amyloplast could not be detected. These data seriously weaken the argument for the selective uptake of triose phosphates by the amyloplast as part of the pathway of starch biosynthesis from sucrose in plant storage tissues. Instead, we suggest that a hexose phosphate such as glucose 1-phosphate, glucose 6-phosphate, or fructose 6-phosphate is the most likely candidate for entry into the amyloplast. A pathway of starch biosynthesis is presented, which is consistent with our data and with the current information on the intracellular distribution of enzymes in plant storage tissues.
191 citations
TL;DR: The presence of this pathway demonstrates that cyanogenic glucosides, typical secondary plant products serve in the metabolism of developing plants as N-storage compounds and do not exclusively exhibit protective functions due to their repellent effect.
Abstract: In the seeds of Hevea brasiliensis, the cyanogenic monoglucoside linamarin (2-β-d-glucopyranosyloxy-2-methylpropionitrile) is accumulated in the endosperm. After onset of germination, the cyanogenic diglucoside linustatin (2-[6-β-d-glucosyl-β-d-glucopyranosyloxy]-2- methylpropionitrile) is formed and exuded from the endosperm of Hevea seedlings. At the same time the content of cyanogenic monoglucosides decreases. The linustatin-splitting diglucosidase and the β-cyanoalanine synthase that assimilates HCN, exhibit their highest activities in the young seedling at this time. Based on these observations the following pathway for the in vivo mobilization and metabolism of cyanogenic glucosides is proposed: storage of monoglucosides (in the endosperm)—glucosylation—transport of the diglucoside (out of the endosperm into the seedling)—cleavage by diglucosidase—reassimilation of HCN to noncyanogenic compounds. The presence of this pathway demonstrates that cyanogenic glucosides, typical secondary plant products serve in the metabolism of developing plants as N-storage compounds and do not exclusively exhibit protective functions due to their repellent effect.
187 citations
TL;DR: It is concluded that in tomato seeds the weakening of endosperms prior to radicle protrusion is mediated by a GA-induced enzymatic degradation of the mannan-rich cell walls.
Abstract: The weakening of the mechanical restraint of the endosperm layer in tomato (Lycopersicon esculentum Mill.) seeds, a prerequisite for germination, has been studied with the use of seeds of the gibberellin (GA)-deficientgib-1 mutant. Incubation ofgib-1 endosperms, including part of the testa, in 10 μM GA4+7, resulted within 12 h in the release of fructose, glucose, galactose and mannose into the incubation medium. Only small amounts of sugars diffused out of thegib-1 endosperms during incubation in water. Chemical hydrolysis of endosperm cell walls ofgib-1 seeds showed that they are mainly composed of mannose, and smaller quantities of glucose and galactose. Treatment with GA4+7 induced in the endosperms the production of endo-β-mannanase activity that was not detectable during incubation in water, and also increased the activities of mannohydrolase and α-galactosidase as compared with the water controls. No cellulase activity was found. It is concluded that in tomato seeds the weakening of endosperms prior to radicle protrusion is mediated by a GA-induced enzymatic degradation of the mannan-rich cell walls.
187 citations
TL;DR: It is suggested that PPi required by UDP-Glc pyrophosphorylase and PPi-linked phosphofructokinase in the endosperm may be supplied by starch synthesis.
Abstract: Tissue distribution and activity of enzymes involved in sucrose and hexose metabolism were examined in kernels of two inbreds of maize (Zea mays L.) at progressive stages of development. Levels of sugars and starch were also quantitated throughout development. Enzyme activities studied were: ATP-linked fructokinase, UTP-linked fructokinase, ATP-linked glucokinase, sucrose synthase, UDP-Glc pyrophosphorylase, UDP-Glc dehydrogenase, PPi-linked phosphofructokinase, ATP-linked phosphofructokinase, NAD-dependent sorbitol dehydrogenase, NADP-dependent 6-P-gluconate dehydrogenase, NADP-dependent Glc-6-P dehydrogenase, aldolase, phosphoglucoisomerase, and phosphoglucomutase. Distribution of invertase activity was examined histochemically. Hexokinase and ATP-linked phosphofructokinase activities were the lowest among these enzymes and it is likely that these enzymes may regulate the utilization of sucrose in developing maize kernels. Most of the hexokinase activity was found in the endosperm, but the embryo had high activity on a dry weight basis. The endosperm, which stores primarily starch, contained high PPi-linked phosphofructokinase and low ATP-linked phosphofructokinase activities, whereas the embryo, which stores primarily lipids, had much higher ATP-linked phosphofructokinase activity than did the endosperm. It is suggested that PPi required by UDP-Glc pyrophosphorylase and PPi-linked phosphofructokinase in the endosperm may be supplied by starch synthesis. Sorbitol dehydrogenase activity was largely restricted to the endosperm, whereas 6-P-gluconate and Glc-6-P dehydrogenase activities were highest in the base and pericarp. A possible metabolic pathway by which sucrose is converted into starch is proposed.
161 citations
TL;DR: This chapter reviews the genetic and molecular aspects of maize endosperm development and leads to useful manipulations to gain increased yields and improved quality.
Abstract: Publisher Summary This chapter reviews the genetic and molecular aspects of maize endosperm development The Zea mays L (maize) endosperm development is generated by both its importance in agriculture and by the opportunity it affords to study developmental mechanisms The endosperm of maize is a large storage organ that constitutes 80–90% of the mature kernel dry weight The mature maize kernel is the result of an integrated developmental process involving both the embryo and the endosperm The development of the endosperm is focused as it relates to overall kernel maturation It leads to useful manipulations to gain increased yields and improved quality The maize endosperm is generally described as having a triploid origin and the development of endosperm tissue in the kernel proceeds at a tremendously fast rate The rapidly growing endosperm gradually replaces the nucleus and ultimately compresses any remaining nuclear cells to the outer edge of the kernel cavity Cross-section preparations of the endosperm show the overall structure consisting of irregularly shaped cells with prominent nuclei and nucleoli
132 citations
TL;DR: It was shown in all 11 transgenic plants obtained that GUS activity was restricted to the endosperm tissue of transgenic tobacco seeds, and zein proteins did not appear to be broken down during tobacco seed germination; synthesis of zeins began in green cotyledons.
Abstract: Transgenic tobacco plants containing maize gene (Z4) encoding a 23-kd zein protein, which is normally synthesized in the endosperm of maize seeds, were obtained using a modified Ti plasmid vector. Although a polyadenylated transcript homologous to the Z4 gene was present in the seeds of some of these transgenic plants, zein protein could not be detected in any of the plants tested (35 total). To simplify the analysis of the tissue specificity of the Z4 promoter (Z4(pro)) in different organs of transformed tobacco plants, additional transgenic plants containing the chimeric genes Z4(pro)-CAT and Z4(pro)-GUS were produced. Very weak seed-specific CAT activity was observed in one out of ten Z4(pro)-CAT-transformed plants. When the more sensitive GUS assay system was used to evaluate Z4(pro) activity in tobacco, it could be shown in all 11 transgenic plants obtained that GUS activity was restricted to the endosperm tissue of transgenic tobacco seeds. To study the synthesis and stability of the zein proteins in different organs of transgenic tobacco plants, the Z4 protein-coding region and also a cDNA clone (A30) encoding a 19-kd zein protein were placed under the control of the 35S promoter (35S(pro)) of cauliflower mosaic virus. Undegraded zein proteins of both size classes were detected in roots, leaves and endosperm tissue, but not embryos, of mature seeds from 35S(pro)-zein-transformed plants. The zein proteins did not appear to be broken down during tobacco seed germination; synthesis of zeins began in green cotyledons.
124 citations
TL;DR: The undermethylated state of storage protein genes of maize, coding for zeins and glutelins, is already established at an early stage of endosperm development, when transcripts levels for both genes are almost undetectable.
Abstract: We investigated the methylation state of a set of storage protein genes of maize, coding for zeins and glutelins, in different somatic tissues and in developing endosperms. These genes, present as multigene families in the maize genome and organized in clusters on different chromosomes, are coordinately and specifically transcribed only in endosperm cells. Southern blot analysis of DNA digested with methylation-sensitive restriction enzymes shows a specific and extensive undermethylation of zein and glutelin sequences in the endosperm, while a common methylated pattern is detected in the different somatic tissues and in the embryo. However, a constant fraction of endosperm DNA (∼35%) is methylated at all zein sequences, which are found to be heavily modified in pollen DNA as well. Undermethylation is extended along a zein cluster and cannot be explained by reduced levels of 5-methylcytosine in endosperm DNA with respect to other tissues. The undermethylated state of storage protein genes is already established at an early stage of endosperm development, when transcripts levels for both genes are almost undetectable.
105 citations
TL;DR: The behaviour of the isolated amyloplasts, and previously published data on the labelling of starch by [13C]glucose, are consistent with the view that in wheat grains it is a C-6, not a C3, compound that enters the amyloplast to provide the carbon for starch synthesis.
Abstract: The aim of this work was to discover which compound(s) cross the amyloplast envelope to supply the carbon for starch synthesis in grains of Triticum aestivum L. Amyloplasts were isolated, on a continuous gradient of Nycodenz, from lysates of protoplasts of endosperm of developing grains, and then incubated in solutions of 14C-labelled: glucose, glucose 1-phosphate, glucose 6-phosphate, fructose 6-phosphate, fructose-1,6-bisphosphate, dihydroxyacetone phosphate and glycerol 3-phosphate. Only glucose 1-phosphate gave appreciable labelling of starch that was dependent upon the integrity of the amyloplasts. Incorporation into starch was linear with respect to time for 2 h. At the end of the incubations, 98% of the 14C in the soluble fraction of the incubation mixture was recovered as [14C]glucose 1-phosphate. Thus it is unlikely that the added [14C glucose 1-phosphate was extensively metabolized prior to uptake by the amyloplasts. It is argued that the behaviour of the isolated amyloplasts, and previously published data on the labelling of starch by [13C]glucose, are consistent with the view that in wheat grains it is a C-6, not a C-3, compound that enters the amyloplast to provide the carbon for starch synthesis.
102 citations
TL;DR: Treatment of the fertilized egg cell with MNU was found to be an effective method to induce mutations for storage proteins in protein bodies of rice.
Abstract: To obtain genetic materials to breed qualitatively improved rice storage proteins, we screened about 3,000 mutant lines induced by the treatment of rice fertilized egg cell with N-methyl-N-nitrosourea (MNU). The screening was performed by comparing the profiles of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with that of the original variety, Kinmaze, especially focussing on the changes in polypeptides present in two kinds of protein bodies, PB-I and PB-II. We selected 17 mutant lines and classified them into 4 types on the basis of variations of the relative contents of the polypeptides. Determination of extracted protein in the starchy endosperm of the mutants revealed changes in the content of prolamin and glutelin but not globulin. In some mutants there was marked accumulation of 57 kDa polypeptide concomitant with the remarkable reduction of glutelin subunits. Treatment of the fertilized egg cell with MNU was found to be an effective method to induce mutations for storage proteins in protein bodies of rice.
87 citations
TL;DR: Results indicate that elevated temperatures significantly reduce the activity of the sucrose cleavage enzyme UDPsucrose synthase (EC 2.4.1.13), found in the endosperm during grain development, and that these effects may be initiated by a relatively short period of thermal stress applied close to anthesis.
Abstract: Starch accumulation is reduced when endosperms develop at elevated temperatures. Reduced starch deposition does not appear to be due to limiting assimilate levels during the grain filling period; on the contrary, endosperm sucrose may even be increased at the elevated temperature. Results indicate that elevated temperatures significantly reduce the activity of the sucrose cleavage enzyme UDPsucrose synthase (EC 2.4.1.13), found in the endosperm during grain development, and that these effects may be initiated by a relatively short period of thermal stress applied close to anthesis. It would appear that, when developing barley ears are exposed to elevated temperatures, there is an irreversible reduction in the capacity of the endosperm to convert sucrose to starch, caused by a decrease in the activity of at least one of the enzymes involved in this conversion pathway.
TL;DR: The 549 base pairs of the 5′ flanking region of a barley seed storage protein (B1 hordein) gene were linked to the reporter gene encoding chloramphenicol acetyl transferase (CAT) and the chimaeric gene was transferred into tobacco plants using Agrobacterium tumefaciens.
Abstract: The 549 base pairs of the 5' flanking region of a barley seed storage protein (B1 hordein) gene were linked to the reporter gene encoding chloramphenicol acetyl transferase (CAT). The chimaeric gene was transferred into tobacco plants using Agrobacterium tumefaciens. CAT enzyme activity was detected in the seeds, but not in the leaves, of the transgenic plants. Furthermore, enzyme activity was found only in the endosperm, and only from fifteen days after pollination. In contrast, the constitutive 19S promoter from cauliflower mosaic virus (CaMV) directed the expression of the CAT gene in the leaves as well as in both the endosperm and embryo and at all stages in seed development.
TL;DR: It is argued that wheat endosperm lacks significant plastidic fructose-1,6-bisphosphatase and that carbon for starch synthesis does not enter the amyloplast as a C-3 compound but probably as hexose phosphate.
Abstract: Lysates of protoplasts from the endosperm of developing grains of wheat (Triticum aestivum) were fractionated on density gradients of Nycodenz to give amyloplasts. Enzyme distribution on the gradients suggested that: (i) starch synthase and ADP-glucose pyrophosphorylase are confined to the amyloplasts; (ii) pyrophosphate: fructose-6-phosphate 1-phosphotransferase and UDP-glucose pyrophosphorylase are confined to the cytosol; (iii) a significant proportion (23-45%) of each glycolytic enzyme, from phosphoglucomutase to pyruvate kinase inclusive, is in the amyloplast. Starch synthase, ADP-glucose pyrophosphorylase and each of the glycolytic enzymes showed appreciable latency when assayed in unfractionated lysates of protoplasts. No activity of fructose-1,6-bisphosphatase was found in amyloplasts or in homogenates of endosperm. Antibody to plastidic fructose-1,6-bisphosphatase did not react positively, in an immunoblot analysis, with any protein in extracts of wheat endosperm. It is argued that wheat endosperm lacks significant plastidic fructose-1,6-bisphosphatase and that carbon for starch synthesis does not enter the amyloplast as a C-3 compound but probably as hexose phosphate.
TL;DR: It is concluded that sequences required for embryo expression, temporal control, and cell specificity are linked to the beta-conglycinin gene, and that factors regulating beta-Conglycin in gene expression are compartmentalized within analogous soybean and tobacco seed regions.
Abstract: We transformed tobacco plants with a soybean β-conglycinin gene that encodes the 1.7-kilobase β-subunit mRNA. We showed that the β-conglycinin mRNA accumulates and decays during tobacco seed development and that β-conglycinin mRNA is undetectable in the tobacco leaf. We utilized in situ hybridization to localize β-conglycinin mRNA within the tobacco seed. β-Conglycinin mRNA is not detectable within the endosperm but is localized within specific embryonic cell types. The highest concentration of β-conglycinin mRNA is found in cotyledon storage parenchyma cells. We conclude that sequences required for embryo expression, temporal control, and cell specificity are linked to the β-conglycinin gene, and that factors regulating β-conglycinin gene expression are compartmentalized within analogous soybean and tobacco seed regions.
TL;DR: Sixty-nine out of 100 florets fixed 48 h after pollination contained an embryo, an endosperm, or both, a remarkably high frequency in view of the taxonomic distance spanned by the cross.
Abstract: Crosses were made between the hexaploid wheat ‘Chinese Spring’ (2n = 42) and the diploid grain sorghum ‘S9B’ (2n = 20). Sixty-nine out of 100 florets fixed 48 h after pollination contained an embryo, an endosperm, or both, a remarkably high frequency in view of the taxonomic distance spanned by the cross. Percentages of single or double fertilization ranged from 50 % to 91 % for individual spikes. The hybrid origin of the embryos was confirmed by examining zygotes from spikes fixed 25 to 27 h after pollination. Seven of the 8 zygotes in which chromosomes were sufficiently contracted to be counted contained 21 large wheat chromosomes and 10 much smaller sorghum chromosomes. The eighth contained 21 chromosomes from wheat and 20 from sorghum. Sorghum chromosomes did not appear to be attached to the spindle in zygote nietaphases and showed no evidence of movement towards the spindle poles in the single zygote anaphase found. Embryos with two or more cells invariably contained one or more micronuclei and metaphases in embryos with three or more cells contained only 21 wheat chromosomes showing that sorghum chromosomes were rapidly eliminated. Endosperm, when present, was always highly abnormal.
TL;DR: The low amylose content of dull mutants is under monogenic recessive control, and two loci, du-1 and du-4, were found to be located on chromosomes 7 and 4, respectively.
Abstract: Eight dull mutants that lower the amylose content of rice endosperm as well as waxy mutant and a cultivar with common grains were crossed in a diallele manner. The amylose content of F1 and F2 seeds was determined on the basis of single grain analysis. It was concluded that the low amylose content of dull mutants is under monogenic recessive control. Alleles for low amylose content are located at five loci designated as du-1, du-2, du-3, du-4 and du-5. These loci are independent of wx locus located on chromosome 6. The five du loci have an additive effect in lowering the amylose content. Two loci, du-1 and du-4, were found to be located on chromosomes 7 and 4, respectively.
TL;DR: The “slender” mutant of barley resembles a normal barley plant treated with high doses of gibberellic acid (GA3), and the results indicate that the endosperm of the slender mutant exhibits similar properties to WT endOSperm treated with GA3, indicating that the slender plants retain sensitivity to ABA.
Abstract: The “slender” mutant of barley resembles a normal barley plant treated with high doses of gibberellic acid (GA3). Expression of GA3-regulated and abscisic acid (ABA)-regulated mRNAs was studied in the endosperm and roots of mutant and wild-type (WT) plants.
TL;DR: A protein antigenic to the IgE antibody of allergic individuals was isolated from rice grain by ion-exchange and gel-filtration chromatographies, and its immunoreactivity was quite stable to heating at 100°C.
Abstract: A protein antigenic to the IgE antibody of allergic individuals was isolated from rice grain by ion-exchange and gel-filtration chromatographies. The molecular weight of the allergenic protein was estimated to be about 16,000 by sodiumdodecylsulfate-gel electrophoresis. The protein contained 7mol of cystine residue per mole of protein and no cysteine residues, and its immunoreactivity was quite stable to heating at 100°C. This allergenic protein was mainly present in the endosperm portion of rice seeds.
TL;DR: The Ca, Mg, K, and P content of dry barley grains and seedlings was investigated using energy dispersive x-ray analysis and neutron activation analysis and showed that the endosperm contained very little Ca in relation to the other three elements.
Abstract: The Ca, Mg, K, and P content of dry barley (Hordeum vulgare) grains and seedlings was investigated using energy dispersive x-ray analysis and neutron activation analysis. Energy dispersive x-ray analysis of protein bodies in aleurone cells showed that these bodies contained very little Ca in relation to P, Mg, and K. Neutron activation analysis also showed that the endosperm contained very little Ca in relation to the other three elements. Surface sterilization and soaking treatments brought about slight loss of Ca but substantial loss of K from embryos. Over 6 days of growth the seedling plant gained minerals from the endosperm.
TL;DR: The formation of anticlinal cell walls, giving rise to openended cell cylinders, coincides with the occurrence of phragmoplast microtubular arrays which were demonstrated during the period of cell wall elongation, suggesting that a general mechanism is involved.
Abstract: The three-dimensional structure of the microtubular cytoskeleton of developing wheat endosperm was investigated immunocytochemically. Semi-thin sections were prepared from polyethylene glycol embedded ovaries. At the free-nuclear stage the endosperm cytoplasm with regularly distributed nuclei surrounded a large central vacuole and exhibited an extensive network of fluorescent labelled microtubular assemblies radiating from each nucleus. As was found in other coenocytes, this particular and nuclear-dependent cytoskeletal configuration functions in the arrangement of nuclei and in the stabilization of the nuclear positions. At the beginning of cellularization of the endosperm the formation of vacuoles altered the radiating networks. It is likely that the radiating microtubular arrays function in the formation of phragmoplasts, independent of nuclear divisions. The formation of anticlinal cell walls, giving rise to openended cell cylinders, coincides with the occurrence of phragmoplast microtubular arrays which were demonstrated during the period of cell wall elongation. The microtubular system radiating from the nuclei in these cell cylinders anchored the nuclei in stage- and locus-specific positions. During the development of aleurone and inner endosperm cells, cell morphogenesis was related to earlier demonstrated types of microtubular configurations in the cortical cytoplasm. This suggests that a general mechanism is involved.
01 Jan 1988
TL;DR: The introduction of a gene encoding a M(r) 19,000 zein protein into petunia by Agrobacterium tumefaciens mediated transformation suggested that DNA sequences responsible for developmental regulation are not readily recognized in petunia plants.
Abstract: Genes encoding maize seed storage proteins, zeins, are expressed in developing endosperm tissue. To determine whether the DNA sequences controlling the developmental expression of these genes are recognized in dicots, we introduced a gene encoding a Mr 19,000 zein protein into petunia by Agrobacterium tumefaciens mediated transformation. Southern blot analysis of DNA fronmregenerated transgenic plants showed that between 1 and 12 copies of the zein gene were integrated at various locations in the petunia genome. S1 nuclease mapping with 5' and 3' probes for zein mRNA showed that transcription of the gene was correctly initiated and terminated in seeds of the transgenic plants. The mRNA was first detected in petunia seeds 10 days after pollination and disappeared 17 days after pollination. However, only small amounts of zein transcripts were synthesized and protein could not be detected at any stage of development. We also found low levels of zein mRNA in leaves, stems, and flowers of the transgenic plants, suggesting that DNA sequences responsible for developmental regulation are not readily recognized in petunia plants.
TL;DR: In this article, the authors introduced a gene encoding a M(r) 19,000 zein protein into petunia by Agrobacterium tumefaciens mediated transformation.
Abstract: Genes encoding maize seed storage proteins, zeins, are expressed in developing endosperm tissue. To determine whether the DNA sequences controlling the developmental expression of these genes are recognized in dicots, we introduced a gene encoding a M(r) 19,000 zein protein into petunia by Agrobacterium tumefaciens mediated transformation. Southern blot analysis of DNA from regenerated transgenic plants showed that between 1 and 12 copies of the zein gene were integrated at various locations in the petunia genome. S1 nuclease mapping with 5' and 3' probes for zein mRNA showed that transcription of the gene was correctly initiated and terminated in seeds of the transgenic plants. The mRNA was first detected in petunia seeds 10 days after pollination and disappeared 17 days after pollination. However, only small amounts of zein transcripts were synthesized and protein could not be detected at any stage of development. We also found low levels of zein mRNA in leaves, stems, and flowers of the transgenic plants, suggesting that DNA sequences responsible for developmental regulation are not readily recognized in petunia plants.
TL;DR: It is suggested that the leaf enzyme and endosperm starch synthase I are the same enzyme and that it is ‘constitutively’ expressed.
TL;DR: Cytosolic pyruvate kinase from endosperm of germinating castor beans has been purified 3100-fold to apparent homogeneity and a final specific activity of 203 micromole pyruVate produced/minute per milligram protein.
Abstract: Cytosolic pyruvate kinase from endosperm of germinating castor beans (Ricinus communis L.; cv Hale) has been purified 3100-fold to apparent homogeneity and a final specific activity of 203 micromole pyruvate produced/minute per milligram protein. Purification steps included: heat treatment, polyethylene glycol fractionation, Q-Sepharose, ADP-agarose, Mono-Q and Phenyl Superose chromatography. Nondenaturing polyacrylamide gel electrophoresis of the final sample resulted in a single protein staining band which co-migrated with pyruvate kinase activity. Two protein staining bands of 57 and 56 kilodaltons were observed following SDS polyacrylamide gel electrophoresis of the final preparation. The native molecular mass was found to be about 240 kilodaltons. This enzyme appears to be a tetramer composed of two different subunits. The presence of dithioerythritol (2 millimolar) was required for optimal activity of the purified enzyme.
TL;DR: In this paper, the authors studied the insoluble carbohydrate and lipid fractions of oil palm (Elaeis guineensis Jacq) kernels prior to and during germination and found that the second largest component of the endosperm is a galactomannan located in the secondary walls of the seed.
TL;DR: Nine plants were regenerated by somatic embryogenesis from endosperm tissue of open-pollinated seeds of Juglans regia L. cv Manregian and have a triploid chromosome number of 3n=48.
Abstract: Plants were regenerated by somatic embryogenesis from endosperm tissue of open-pollinated seeds of Juglans regia L. cv Manregian. These plants were obtained by growing endosperm tissue on media similar to those used for plant regeneration from walnut cotyledons (Tulecke and McGranahan 1985). The plants appear morphologically uniform and have a triploid chromosome number of 3n=48. Nine plants have been grown to a young sapling stage in soil. This embryogenic line from endosperm has been maintained in culture for two years by the process of repetitive somatic embryogenesis.
TL;DR: In this paper, full-length cDNA clones for barley chymotrypsin inhibitor 1 (CI-1) have been isolated from an endosperm-specific cDNA library.
Abstract: Full-length cDNA clones for barley chymotrypsin inhibitor 1 (CI-1) have been isolated from an endosperm-specific cDNA library. Hybridization and nucleotide sequence analyses indicate that these cDNAs represent two distinct types of CI-1 mRNA which we have called CI-1A and CI-1B. Both mRNAs encode polypeptides of 83 residues (M
r=8790 and 8960) which differ at eleven positions. The full-length cDNA sequences do not predict N-terminal signal peptide extensions indicating that CI-1 is synthesized in the mature form in contrast to the homologous proteinase inhibitors of tomato and potato. Northern hybridization experiments show that the CI-1 genes are under strict developmental and organ-specific control. CI-1 transcripts were first detected in the developing barley endosperm between 12 and 14 days after anthesis but no CI-1-related sequences were detected in the RNA preparations from shoots, leaves or roots. The expression of CI-1 was also studied in the high-lysine barley mutants Hiproly, Riso 56 and Riso 1508. Approximately 15-fold (Hiproly) and 4-fold (Riso 56 and 1508) higher levels of CI-1 mRNA were detected in the mutant endosperms compared to normal barley. These results correlate well with the increased deposition of CI-1 in the high-lysine lines and show that the differential expression is controlled mainly at the level of transcription or stability of the mRNA. Using Southern-blots of barley DNA we estimate that there are three copies of CI-1 per haploid genome in both normal and mutant barley lines.
TL;DR: The majority of the proteins were similar in molecular mass and charge in the two tissues, suggesting that most of the storage proteins are probably the same, however, there were also several embryo- and endosperm-specific proteins apparent in both the first- and second-dimension gels.
Abstract: Comparative studies on the ultrastructure and protein composition of the embryo and endosperm of date palm (Phoenix dactylifera L.) were conducted. Cells of the embryo cotyledon and endosperm function in reserve storage and contained cell walls, nuclei, and cytoplasm rich in lipid and protein bodies. Morphometric analysis from light and electron micrographs showed that the cell walls of the endosperm occupied 65% of the total cell volume, but only 6% in the embryo. The protein bodies of the endosperm accounted for 11%, whereas those of the embryo occupied more than half of the total cell volume. The volume of organelles and organelle-free cytoplasm in the endosperm was negligible, suggesting that most of the extractable endosperm proteins are localized in the protein bodies. Extractable proteins in the embryo may come from cytoplasm, protein bodies, and other organelles. The endosperm contains relatively lower amounts of proteins than does the embryo. Proteins extracted from both tissues were compared using SDS-polyacrylamide gel electrophoresis, tube gel isoelectric focusing, and two-dimensional electrophoresis. Proteins of both the tissues were heterogeneous in molecular mass and charge. The majority of the proteins were similar in molecular mass and charge in the two tissues, suggesting that most of the storage proteins are probably the same. However, there were also several embryo- and endosperm-specific proteins apparent in both the first- and second-dimension gels. The endosperm-specific proteins may play an important role in germination and seedling development.
TL;DR: Evidence is presented to show that pyruvate decarboxylase contributes to apparent acetolactate synthase activity in crude embryo extracts and a modification of the acetolactic synthase assay is proposed to correct for the presence of pyruve decar boxylase in unpurified plant homogenates.
Abstract: Acetolactate synthase (EC 4.1.3.18) activity was examined in maize (Zea mays L.) endosperm and embryos as a function of kernel development. When assayed using unpurified homogenates, embryo acetolactate synthase activity appeared less sensitive to inhibition by leucine + valine and by the imidazolinone herbicide imazapyr than endosperm acetolactate synthase activity. Evidence is presented to show that pyruvate decarboxylase contributes to apparent acetolactate synthase activity in crude embryo extracts and a modification of the acetolactate synthase assay is proposed to correct for the presence of pyruvate decarboxylase in unpurified plant homogenates. Endosperm acetolactate synthase activity increased rapidly during early kernel development, reaching a maximum of 3 micromoles acetoin per hour per endosperm at 25 days after pollination. In contrast, embryo activity was low in young kernels and steadily increased throughout development to a maximum activity of 0.24 micromole per hour per embryo by 45 days after pollination. The sensitivity of both endosperm and embryo acetolactate synthase activities to feedback inhibition by leucine + valine did not change during kernel development. The results are compared to those found for other enzymes of nitrogen metabolism and discussed with respect to the potential roles of the embryo and endosperm in providing amino acids for storage protein synthesis.
TL;DR: The highlyregulated expression of zein genes in endosperm tissue suggests that trans-acting factors, by binding to cis-acting sequences, influence the coordinate and developmentally regulated expression of these genes.
Abstract: The highly regulated expression of zein genes in endosperm tissue suggests that trans-acting factors, by binding to cis-acting sequences, influence the coordinate and developmentally regulated expression of these genes. A 15 55 bp 5′ flanking region of a zein gene was analysed for sites of specific interaction with nuclear proteins from endosperm and seedling tissue. At least four different protein binding sites were mapped to the zein 5′ region by the nitrocellulose filter binding technique and two of these exhibit tissue-specific binding.