Showing papers on "Endosperm published in 1986"
TL;DR: Starch exists inside the endosperm of cereals enmeshed in a protein matrix, which is particularly strong in sorghum and corn, and both the starch granules and the protein matrix around them are more digestible in waxy grain.
Abstract: Starch exists inside the endosperm of cereals enmeshed in a protein matrix, which is particularly strong in sorghum and corn. Starch digestibility is affected by the plant species, the extent of starch-protein interaction, the physical form of the granule, inhibitors such as tannins, and the type of starch. Among the cereals, sorghum generally has the lowest starch digestibility. The resistance to digestive action of the hard peripheral endosperm layer is largely responsible for this effect. Processing methods such as steam-flaking and reconstitution are effective in raising sorghum digestibility to near that of corn. Waxy sorghum shows consistently higher feeding value than normal sorghum. Both the starch granules and the protein matrix around them are more digestible in waxy grain. The development of new heterowaxy or waxy sorghum hybrids may further increase sorghum feed efficiency.
607 citations
Journal Article•
345 citations
TL;DR: A 650-nucleotide cDNA from barley aleurone layers encoding a protein that is closely related to a known α-amylase inhibitor from Indian finger millet, and that has homologies to certain plant trypsin inhibitors is cloned and sequenced.
Abstract: We have cloned and sequenced a 650-nucleotide cDNA from barley (Hordeum vulgare L.) aleurone layers encoding a protein that is closely related to a known α-amylase inhibitor from Indian finger millet (Eleusine coracana Gaertn.), and that has homologies to certain plant trypsin inhibitors. mRNA for this probable amylase/protease inhibitor (PAPI) is expressed primarily in aleurone tissue during late development of the grain, as compared to that for the amylase/subtilisin inhibitor, which is expressed in endosperm during the peak of storage-protein synthesis. PAPI mRNA is present at high levels in aleurone tissue of desiccated, mature grain, and in incubated aleurone layers prepared from rehydrated mature seeds. Its expression in those layers is not affected by either abscisic acid or gibberellic acid, hormones that, respectively, increase and decrease the abundance of mRNA for the amylase/subtilisin inhibitor. PAPI mRNA is almost as abundant in gibberellic acid-treated aleurone layers as that for α-amylase, and PAPI protein is synthesized in that tissue at levels that are comparable to α-amylase. PAPI protein is secreted from aleurone layers into the incubation medium.
184 citations
TL;DR: High-efficiency genetic transformation was induced in a genetic stock of maize by self-pollination of the recipient plants along with DNA of the donor, and exogenous DNA that had entered into the embryo had been maintained through embryo formation, germination, vegetative growth and differentiation, and reproductive growth.
Abstract: High-efficiency genetic transformation was induced in a genetic stock of maize, Zea mays Linnaeus, by self-pollination of the recipient plants along with DNA of the donor. The highest frequency of transformed endosperm per ear was 9.29%. DNA was applied onto silks in a pollen/DNA pasty mixture. The exogenous DNA transferred into endosperm expressed itself in endosperm formation. It is not known, however, whether the exogenous DNA segment in endosperm had been incorporated or whether it was present in the nucleus additionally, fragmentally, or in some other state. It was revealed that all of four possible cases had occurred as follows: exogenous DNA was transferred into (i) both embryo and endosperm of the same kernel, (ii) embryo only, (iii) endosperm only, and (iv) neither embryo nor endosperm. It was also revealed that exogenous DNA that had entered into the embryo had been maintained through embryo formation, germination, vegetative growth and differentiation, and reproductive growth, and finally was manifested in embryo and/or endosperm of the following generation and acted in endosperm formation. The frequency of transformed endosperm in this generation, however, was rather low. It may be that exogenous DNA taken into the embryo was unstable.
158 citations
156 citations
TL;DR: The development of a fungal endophyte in the tissue of Lolium perenne during flowering, seed set, and germination is described and hyphae outside the embryo appear to play no further part in invasion of the already infected embryo.
Abstract: The development of a fungal endophyte in the tissue of Lolium perenne during flowering, seed set, and germination is described. The endophyte progresses intercellularly from the vegatative apex into the inflorescence primordium and floral apices, from where it penetrates the tissues of ovary and ovule. At megagametophyte maturity, hyphae are concentrated outside its wall adjacent to the large lateral antipodal cells and subsequently gain entry to the embryo sac, probably soon after fertilisation. During early embryogenesis, hyphae occur on the surface of the embryo, and penetrate it at the ‘notched’ stage. At seed maturity, hyphae are widespread within the embryo, including the plumule apex, as well as below the testa, between cells of the aleurone layer, and between scutellum and endosperm. At germination, hyphae outside the embryo appear to play no further part in invasion of the already infected embryo. The endophyte of Festuca arundinacea has a similar relationship with its host and appears t...
134 citations
TL;DR: The complete sequence of the aleurone (1-->3,1-->4)-beta-glucanase isoenzyme II comprises 306 amino acids and was determined by sequencing nine tryptic peptides and aligning them with the amino acid sequence deduced from a cDNA clone encoding the 291 NH(2)-terminal residues.
Abstract: During germination of barley grains, the cell walls of the starchy endosperm are degraded by (1→3,1→4)-β-glucanases (EC 3.2.1.73) secreted from the aleurone and scutellar tissues. The complete sequence of the aleurone (1→3,1→4)-β-glucanase isoenzyme II comprises 306 amino acids and was determined by sequencing nine tryptic peptides (110 residues) and aligning them with the amino acid sequence deduced from a cDNA clone encoding the 291 NH2-terminal residues. Although no amino acid sequence homology with a bacterial (1→3)(1→4)-β-glucanase is apparent, close to 50% homology is found with two large regions of a (1→3)-β-glucanase from tobacco pith tissue. The gene for barley (1→3,1→4)-β-glucanase isoenzyme II shares with that for the α-amylase isoenzyme 1 a strongly preferred use of codons with G and C in the wobble position (94% and 90%, respectively). Both enzymes are secreted from the aleurone cells during germination. Such one-sided codon usage is not characteristic for the gene encoding the (1→3)-β-glucanase of tobacco pith tissue or the hor2-4 gene encoding the B1 hordein storage protein in the endosperm.
106 citations
TL;DR: Two types of response to temperature appear to be involved: a comparatively low temperature optimum for starch synthesis, and an irreversible reduction in the capacity of the endosperm to convert sucrose to starch resulting from exposure of the ears, or the grains themselves, to elevated temperature.
Abstract: Elevated temperature during grain filling resulted in reduced single grain weight due largely to an effect of temperature on the accumulation of starch in the endosperm. Wheat endosperm was cultured in vitro on solutions of [14C]sucrose and the responses to variation in temperature within the range 15-35°C were evaluated in terms of the absorption of radioactive sugar, the evolution of 14CO2, and the incorporation of radioactivity into starch. At 35°C the level of 14C in the intracellular pool of soluble carbohydrate was higher than it was at 30°C, and the average Q,10 for 14CO2 production was 2.1. Incorporation of 14C into starch was greater at 30°C than at 25°C, but at 35°C only half as much [14C]starch was produced compared with that at 30°C. Residual effects of exposure of ears to brief episodes of elevated temperature were investigated by culturing endosperm isolated from such ears on [14C]sucrose at a standard temperature (25°C). Two days of exposure resulted in greater amounts of [14C]starch produced, due to accelerated starch depo- sition, but longer periods (4-6 days) at elevated temperature resulted in substantial reductions in [14C]starch deposition. Exposure to elevated temperature also hastened the onset of chlorophyll degradation in the pericarp of the grain. Two types of response to temperature appear to be involved: a comparatively low temperature optimum for starch synthesis, and an irreversible reduction in the capacity of the endosperm to convert sucrose to starch resulting from exposure of the ears, or the grains themselves, to elevated temperature.
99 citations
TL;DR: The notion that the maize transposable elements may serve a function in natural populations to generate genetic diversity, in this case, proteins with new enzymatic properties is supported.
Abstract: The waxy (wx) locus of maize encodes an enzyme responsible for the synthesis of amylose in endosperm tissue. The phenotype of the Dissociation (Ds) insertion mutant wx-m1 is characterized by endosperm sectors that contain different levels of amylose. We have cloned the Wx gene from this allele and from two germinal derivatives, S5 and S9, that produce intermediate levels of amylose. The Ds insertion in wx-m1 is in exon sequences, is 409 bp in length and represents an example of a class of Ds elements that are not deletion derivatives of the Activator (Ac) controlling element. The two germinal derivatives, S5 and S9, lack the Ds element but contain an additional 9 and 6 bp, respectively, at the site of Ds insertion. The level of Wx mRNA and Wx protein in S5 and S9 is essentially the same as in normal endosperm tissue but Wx enzymatic activity is reduced. Thus, the lesions in S5 and S9 lead to the addition of amino acids in the Wx protein, resulting in Wx enzymes with altered specific activities. This work supports the notion that the maize transposable elements may serve a function in natural populations to generate genetic diversity, in this case, proteins with new enzymatic properties.
98 citations
TL;DR: In zymograms using nondenaturing polyacrylamide gel electrophoresis followed by activity staining, the slowest migrating band represented the most temperature sensitive isozyme and it was suggested that in vivo heat inactivation of soluble starch synthase may be a direct effect of heat on the enzyme protein and that of bound enzyme an indirect effect involving metabolic factors.
Abstract: The effect of temperature on accumulation of starch was studied in grain slices of wheat (Triticum aestivum cv SUN9E), taken 15 days after anthesis. As compared with pretreatment of such slices at 25 degrees C, pretreatment at 30 or 35 degrees C reduced the subsequent conversion of sucrose to starch. In contrast to rice (Oryza sativa cv Calrose), pretreatment of wheat soluble starch synthase in vitro at 30 degrees C or higher temperatures reduced its activity. In zymograms using nondenaturing polyacrylamide gel electrophoresis followed by activity staining, the slowest migrating band represented the most temperature sensitive isozyme. Although preincubation of a soluble enzyme sample in vitro at 25 degrees C did not result in loss of starch synthase activity, it did result in a gradual shift of zymogram banding pattern toward faster migrating species. Pretreatment of isolated starch granules at 40 degrees C increased their bound starch synthase activity. Both soluble and bound enzymes in the grains of whole wheat plants lost activity when the plants were held above 30 degrees C for 30 minutes or longer. Both activities lost from the grains after a 1 hour treatment at 37 degrees C were restored in 1 to 2 days by a return to 21 degrees C. In slices, inactivation of the soluble starch synthase was increased by incubation with 2,4-dinitrophenol. It is tentatively suggested that in vivo heat inactivation of soluble starch synthase may be a direct effect of heat on the enzyme protein and that of bound enzyme an indirect effect involving metabolic factors.
92 citations
TL;DR: The authors' observations strongly implicate the movement of assimilates from the sieve tubes and across the crease tissues as important control points in grain filling.
Abstract: Gradients along the transport pathway from the peduncle to the endosperm cavity were examined during grain filling in wheat. Sieve tube exudate was collected from severed aphid stylets established on the peduncle and rachis and on the vascular bundles in the creases of grains. Phloem exudate could also be collected from broken grain pedicels, and by puncturing the vascular bundle in the grain crease with a needle. Stylets on excised grains persisted exuding, indicating that grain sieve tubes are capable of loading solutes. There was little, if any, discernible gradient in osmolality or solute composition (sucrose, total amino acids) of sieve tube contents along the phloem pathway from the peduncle to the rachis or along the rachis itself. Neither was a gradient detected in osmolality along the sieve tube pathway from the rachis through the rachilla and grain stalk to the crease. Demonstrable solute gradients occurred only across those tissues of the grain crease between the crease sieve tubes and the endosperm cavity, a distance of just 1 millimeter. However, while the sucrose concentration in the sieve tubes was almost tenfold that in the endosperm cavity sap, total amino acids were only threefold higher, and the potassium concentrations of the two were equal. Our observations strongly implicate the movement of assimilates from the sieve tubes and across the crease tissues as important control points in grain filling.
TL;DR: The proteases represent the GA(3)-induced, de novo synthesized proteases that are mainly responsible for the degradation of endosperm storage proteins.
Abstract: Carboxypeptidase and protease activities of hormone-treated barley (Hordeum vulgare cv Himalaya) aleurone layers were investigated using the substrates N-carbobenzoxy-Ala-Phe and hemoglobin. A differential effect of gibberellic acid (GA(3)) on these activities was observed. The carboxypeptidase activity develops in the aleurone layers during imbibition without the addition of hormone, while the release of this enzyme to the incubation medium is enhanced by GA(3). In contrast, GA(3) is required for both the production of protease activity in the aleurone layer and its secretion. The time course for development of protease activity in response to GA(3) is similar to that observed for alpha-amylase. Treating aleurone layers with both GA(3) and abscisic acid prevents all the GA(3) effects described above. Carboxypeptidase activity is maximal between pH 5 and 6, and is inhibited by diisopropylfluorophosphate and p-hydroxymercuribenzoate. We have observed three protease activities against hemoglobin which differ in charge but are all 37 kilodaltons in size on sodium dodecyl sulfate polyacrylamide gels. The activity of the proteases can be inhibited by sulfhydryl protease inhibitors, such as bromate and leupeptin, yet is enhanced by 2-fold with 2-mercaptoethanol. In addition, these enzymes appear to be active against the wheat and barley storage proteins, gliadin and hordein, respectively. On the basis of these characteristics and the time course of GA(3) response, it is concluded that the proteases represent the GA(3)-induced, de novo synthesized proteases that are mainly responsible for the degradation of endosperm storage proteins.
TL;DR: A comprehensive picture of the distribution of proteins in two low-tannin sorghum cultivars was obtained by hand-dissection of the kernels into their anatomical parts: endosperm, germ and pericarp, and it was found that these proteins were rich in essential amino acids, especially lysine.
Journal Article•
TL;DR: McDonough et al. as discussed by the authors studied the microstructure of finger millet using scanning electron and fluorescence microscopies and found that the outer layer was the only testa layer that autofloresced, suggesting the presence of phenolic acids, i.e., ferulic acid.
TL;DR: Overall results show that the periphery of starch granules is the major site of deposition for bound β-amylase in dry seeds, resulting in the conversion of free β-Amylase into a bound form during the desiccation phase of seed development.
Abstract: Association of β-amylase with starch granules in the starchy endosperm of barley (Hordeum vulgare L. cv. Menuet) grains was characterized biochemically. In whole homogenates of dry seeds, two forms of β-amylase were detected: one is free β-amylase extractable with saline solution and the other is bound β-amylase extractable with saline solution containing a reducing agent. The two forms of β-amylase were shown to be identical in terms of mobility on disc gels, antigenicity, and molecular specific activity, indicating that the β-amylase molecules of the two forms are identical. The starch granules were isolated from either dry seeds or mature seeds harvested before the desiccation phase. Both starch granule preparations were morphologically identical by microscopic inspection. The bound β-amylase was predominantly associated with starch granules isolated from dry seeds, whereas it was not associated with starch granules from mature seeds harvested before desiccation. Overall results show that the periphery of starch granules is the major site of deposition for bound β-amylase in dry seeds. The association of β-amylase with starch granules occurs during the desiccation phase of seed development, resulting in the conversion of free β-amylase into a bound form.
TL;DR: Results show that mRNAs encoding PAPI and CI-1 survive seed dessication and are long-lived in aleurone cells, and expression of genes encoding ASI, PSI, protein C, and PAPI is tissue and stage-specific during seed development.
Abstract: To widen the selection of proteins for gene expression studies in barley seeds, experiments were performed to identify proteins whose synthesis is differentially regulated in developing and germinating seed tissues. The in vitro synthesis of nine distinct barley proteins was compared using mRNAs from isolated endosperm and aleurone tissues (developing and mature grain) and from cultured (germinating) aleurone layers treated with abscisic acid (ABA) and GA3. B and C hordein polypeptides and the salt-soluble proteins β-amylase, protein Z, protein C, the chymotrypsin inhibitors (CI-1 and 2), the α-amylase/subtilisin inhibitor (ASI) and the inhibitor of animal cell-free protein synthesis systems (PSI) were synthesized with mRNA from developing starchy endosperm tissue. Of these proteins, β-amylase, protein Z, and CI- 1 and 2 were also synthesized with mRNA from developing aleurone cells, but ASI, PSI, and protein C were not. CI-1 and also a probable amylase/protease inhibitor (PAPI) were synthesized at high levels with mRNAs from late developing and mature aleurone. These results show that mRNAs encoding PAPI and CI-1 survive seed dessication and are long-lived in aleurone cells. Thus, expression of genes encoding ASI, PSI, protein C, and PAPI is tissue and stage-specific during seed development. Only ASI, CI-1, and PAPI were synthesized in significant amounts with mRNA from cultured aleurone layers. The levels of synthesis of PAPI and CI-1 were independent of hormone treatment. In contrast, synthesis of α-amylase (included as control) and of ASI showed antagonistic hormonal control: while GA promotes and ABA reduces accumulation of mRNA for α-amylase, these hormones have the opposite effect on ASI mRNA levels.
TL;DR: The results from immuno-blot analyses show that the Sh encoded sucrose synthetase-1 protein (SS-1) is indeed present in seedlings and provides a new dimension and a useful tool for the analysis of many sh mutants and their revertants due to various transposable elements.
Abstract: The shrunken (sh) locus on chromosome nine in maize has been considered to be endosperm specific at the biochemical and the phenotypic levels of expression. The recent evidence concerning the presence of Sh encoded transcripts in the seedling (Springer et al. 1985) led us to examine this aspect at the protein level. The results from immuno-blot analyses show that the Sh encoded sucrose synthetase-1 protein (SS-1) is indeed present in seedlings. The expression of the gene SS-1 in seedling roots is verifiable by two criteria: 1) Various sh-null mutants that lack the SS-1 protein in the developing endosperm are also devoid of this protein in seedling root extracts. Only a single band, presumably encoded by the SS-2 locus, is seen in these mutants. 2) The electrophoretic variant of the sh mutant encoding a slow migrating SS-1 protein in the endosperm exhibits a concomitantly altered pattern of SS isozymes in seedling roots. A notable feature of SS-1 and SS-2 expression is that a unique tissue specific difference between endosperm and seedling roots is retained. The Sh root extracts show a total of five SS isozymes due to protomeric interaction of the SS1-SS2 tetramers present in the same cell. Endosperm extracts of the same genotype show only SS-1 and SS-2 homomers. The lack of heteropolymers is indicative of spatial and/or temporal separation of SS-1 and SS-2 expression in the endosperm cells. We suggest that these observations provide a new dimension and a useful tool for the analysis of many sh mutants and their revertants due to various transposable elements.
TL;DR: The results do not implicate sucrose synthase as the "rate limiting" enzyme in wheat kernel growth, but they do emphasize the importance of suc rose synthase activity in larger or more rapidly growing kernels, as compared to smaller slower growing kernels.
Abstract: Past research on kernel growth in wheat (Triticum aestivum) has shown that the kernel itself largely regulates the influx of sucrose for consequent starch synthesis in the endosperm of the grain. The first step in the conversion of sucrose to starch is catalyzed by sucrose synthase (EC 2.4.13). Sucrose synthase activity was assayed in developing endosperms from kernels differing in growth rate and in maximum dry weight accumulation. From 10 to 22 days after anthesis, sucrose synthase activity per wheat endosperm remained constant with respect to time in all grains. However, kernels which had higher rates of kernel growth and which achieved greatest maximum weight had consistently and significantly higher sucrose synthase activities at any point in time than did kernels with slower rates of dry matter accumulation and lower maximum weight. In addition, larger kernels had a significantly greater amount of water in which this activity could be expressed. Although the results do not implicate sucrose synthase as the “rate limiting” enzyme in wheat kernel growth, they do emphasize the importance of sucrose synthase activity in larger or more rapidly growing kernels, as compared to smaller slower growing kernels.
TL;DR: Study of soluble protein from wheat, rice, and corn indicated that in cereals there are at least two tissue specific forms of ADPglucose pyrophosphorylase that are encoded by distinct mRNA transcripts, and analysis of genomic DNA by Southern blotting suggested that ADPblots is encoded by a small gene family.
Abstract: Western blots of soluble protein from wheat, rice, and corn showed that ADPglucose pyrophosphorylase subunits have a size of 50 kilodaltons from endosperm tissue and 43 and 46 kilodaltons from leaf. Antisera to ADPglucose pyrophosphorylase precipitated in vitro translation products of 73 and 76 kilodaltons when leaf poly(A)+ RNA was used, whereas endosperm mRNA directed the synthesis of 50 and 56 kilodalton polypeptides. To further study the nature of these mRNA species, an ADPglucose pyrophosphorylase cDNA clone from rice endosperm polyadenylated RNA was obtained and used as a hybridization probe. Northern blots showed that ADPglucose pyrophosphorylase mRNA was slightly larger in leaf (2100 bases) than in endosperm tissue (1900 bases). These studies indicated that in cereals there are at least two tissue specific forms of ADPglucose pyrophosphorylase that are encoded by distinct mRNA transcripts. Analysis of genomic DNA by Southern blotting suggested that ADPglucose pyrophosphorylase is encoded by a small gene family.
TL;DR: Alanine and glutamate appeared to be moving from the sieve tube to the endosperm cavity in the absence of, or perhaps even against, their concentration gradients, suggesting it is transported in a different form.
Abstract: The amino acid composition of endosperm cavity sap and of sieve tube saps from the flag leaf, peduncle, rachis, grain pedicel, and grain were determined for wheat plants just past the mid-half of grain filling. On a mole percent basis, glutamine accounted for almost half of the amino acids in sieve tube sap from the peduncle and ear. Other protein amino acids, plug γ-aminobutyrate, were present in varying, but mostly low (a few mole percent) proportions. The amino acid composition of phloem exudate resembled that of the mature wheat grain. The proportions of amino acids in the endosperm cavity were generally similar to those of the sieve tube sap supplying the grain. Cysteine, however, while virtually absent from sieve tube sap, comprised 1 to 2 mole percent of amino acids in the endosperm cavity, suggesting it is transported in a different form. Also, alanine and, to a lesser extent, glutamate were relatively more prominent in endosperm cavity sap than in the sieve tube sap. Thus, while most amino acids were more concentrated in the sieve tube sap than in the endosperm cavity sap, alanine and glutamate appeared to be moving from the sieve tube to the endosperm cavity in the absence of, or perhaps even against, their concentration gradients.
TL;DR: In this article, the cell walls were extracted from endosperm of five spring and four winter barley varieties of contrasting malting quality and the major phenolic acid was identified by thin-layer chromatography.
TL;DR: Differences in levels of proteins accumulated were found however by comparing in vivo and in vitro synthesized gliadins and non-storage proteins suggesting an additional level of control of protein synthesis during grain development.
TL;DR: The pattern of expression in the earliest stages of development was strikingly similar to that of coleoptile, another rapidly growing, nonphotosynthetic tissue, which reflects the program of development observed cytologically.
Abstract: The developmental accumulation pattern of messenger RNA transcripts and polypeptides for wheat gliadins and ADPglucose pyrophosphorylase was determined using cDNA and antibody probes. Gliadin mRNA was detected on Northern and RNA dot blots at 3 days after flowering, it increased 100-fold by 10 days and decreased subsequent to 14 days. The abundant mRNAs encoding alpha/beta- and gamma-type gliadins and mRNA for ADPglucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis, accumulated coordinately. Despite the coordinate accumulation of their mRNA transcripts, the accumulation of gliadin and ADPglucose pyrophosphorylase polypeptides, as determined by Western blot, differed significantly. The time at which gliadin and ADPglucose pyrophosphorylase mRNAs began accumulating was also the time when the overall pattern of gene expression, as seen by two-dimensional gel electrophoresis of in vitro translation products, changed most significantly. However, the accumulation of a number of other mRNAs or polypeptides having unknown function occurred at other times during endosperm development. The pattern of expression in the earliest stages of development was strikingly similar to that of coleoptile, another rapidly growing, nonphotosynthetic tissue. Thus, the pattern of gene expression reflects the program of development observed cytologically.
TL;DR: The possible mechanism and evolutionary implications of gene-dosage compensation in polyploid wheat are discussed.
Abstract: Several aneuploid lines and one intervarietal substitution line of the hexaploid wheat Triticum aestivum (2n = 6x = 42; genomes AABBDD) cv. Chinese Spring were used to study the effects of different doses of chromosomes 1B, 1D, or 1A on the amount of the high molecular weight (“HMW”) glutenins and gliadins of endosperm. These homeologous chromosomes carry HMW glutenin and gliadin gene clusters on their long and short arms, respectively. Increasing the dosage of chromosome 1B of Chinese Spring in plants having in their 3n endosperm zero or the normal three doses of the homeologue 1D, as well as in plants carrying in their endosperm one dose of 1B of the cultivar Timstein, had a dual effect: on one hand, a nonlinear increase in the amount of each subunit encoded by the chromosome whose dosage was elevated and, on the other hand, a compensating nonspecific decrease in the amount of other HMW glutenin and gliadin subunits encoded either by the homeoalleles on 1D or by the homoalleles on 1B of Timstein, respectively. Deletion of chromosome arm 1BL, which carries only a few HMW glutenin genes, had no significant effect on the amount of HMW glutenins encoded by 1DL and HMW gliadins encoded by 1DS and 1BS. However, deletion of 1BS or 1DS, each carrying many gliadin genes, caused a significant but nonspecific increase in the HMW glutenins and gliadins encoded by the remaining arms of 1B and 1D. The possible mechanism and evolutionary implications of gene-dosage compensation in polyploid wheat are discussed.
TL;DR: Results show that leucoplasts, though specialized for fatty acid biosynthesis and not photosynthesis, have a mechanism of protein import similar to that of chloroplasts.
Abstract: Intact leucoplasts from the endosperm of developing castor oil seed were isolated by Percoll density gradient centrifugation. The precursor to the small subunit of ribulose 1,5-bisphosphate carboxylase from pea was synthesized in vitro from hybrid-selected mRNA. Leucoplasts imported this precursor by an ATP-requiring mechanism similar to that described in chloroplasts (AR Grossman et al. 1980 Nature 285: 625-628). The small subunit precursor was processed to a molecular weight that was identical with that of the mature pea small subunit. These results show that leucoplasts, though specialized for fatty acid biosynthesis and not photosynthesis, have a mechanism of protein import similar to that of chloroplasts.
TL;DR: Results indicate that phytochrome influence on cellulase is not an indirect consequence of the stimulus of germination and that the continuous presence of Pfr is required for the cellulase activity to remain high.
Abstract: Sanchez, R A, de Miguel, L and Mercuri, O 1986 Phytochrome control of cellulase activity in Datura ferox L seeds and its relationship with germination—J exp Bot 37: 1574-1580 The influence of phytochrome on endosperm softening and cellulase activity was studied on light-stimulated Datura ferox seeds Endosperm softening preceded the earliest signs of radicle protrusion, and there was good correlation between the % of seeds with soft endosperm at 48 h after R and germination at 96 h after R Cellulase activity was stimulated by R and the increase in activity preceded, by more than 24 h, radicle protrusion and endosperm softening The effect of R was reversed by FR, but, by delaying the irradiation with FR until cellulase activity had increased significantly, it was observed that removing Pfr did more than just stop any further increase, the level of cellulase activity decreased in about 24 h close to the dark controls Cellulase activity was decreased by a FR irradiation even when more than 60% germination had escaped from reversion These results indicate that phytochrome influence on cellulase is not an indirect consequence of the stimulus of germination and that the continuous presence of Pfr is required for the cellulase activity to remain high The possibility that cellulase and other degrading enzymes may be part of the mechanism of light-induced germination is discussed
TL;DR: The DNase I sensitivity of the nuclear genes encoding the NADPH-protochlorophyllide oxidoreductase, the light-harvesting chlorophyll a/b protein, the hordeins and a 15-kDa protein was assayed in chromatin of etiolated and green leaves and endosperm tissue of barley.
Abstract: The DNase I sensitivity of the nuclear genes encoding the NADPH-protochlorophyllide oxidoreductase, the light-harvesting chlorophyll a/b protein (LHCP), the hordeins and a 15-kDa protein of unknown function was assayed in chromatin of etiolated and green leaves and endosperm tissue of barley (Hordeum vulgare L.).
A tissue-specific differentiation of chromatin structure was found for the LHCP, hordein and 15-kDa protein genes. The genes for the LHCP and the 15-kDa protein, which are expressed in leaf tissue, display DNase I sensitivity in leaves but not in endosperm. Hordein genes which are expressed solely in endosperm, were insensitive to low levels of digestion with DNase I in leaves but sensitive in endosperm. The effect of light on chromatin structure was determined by comparing leaves of etiolated plants and plants which had been grown under a day/night cycle. Only in the case of the 15-kDa protein is there a remarkable change from a DNAse-I-sensitive configuration in etiolated leaves to a more resistant one in leaves from illuminated plants. The gene for the NADPH-protochlorophyllide oxidoreductase was found to be equally sensitive to DNase I in leaves and endosperm.
TL;DR: The cellular localization of β-amylase in resting barley seeds was investigated by immunohistochemistry and it was shown that the ratio between the amounts of enzyme in embryo and endosperm was less than 1/3000.
Abstract: The cellular localization of β-amylase (EC 3.2.1.2) in resting barley seeds was investigated by immunohistochemistry. The monospecificity of the antibodies used was shown by immunoelectrophoresis and western blotting. An adaptation of the immunofluorescence technique allowed the localization of β-amylase. free of autofluorescence, in the different parts of the seed. In endosperm, there was β-amylase protein in aleurone layers, only in the starchy endosperm, where the distribution of the enzyme was not uniform. The β-amylase of starchy endosperm. which can be in a free or a hound form, was mainly localized around starch granules of different sizes. In the embryo. β-amylase was present only in the part of the scutellum in front of the first leaf. By immunoquantitation after separation of the seed parts, its was shown that the ratio between the amounts of enzyme in embryo and endosperm was less than 1/3000.