Showing papers on "Endosperm published in 1985"

Nucleotide sequence of a B1 hordein gene and the identification of possible upstream regulatory elements in endosperm storage protein genes from barley, wheat and maize

Abstract: The B-hordeins are the major group of prolamin storage proteins in barley (Hordeum vulgare L.) and they are encoded by a small multigene family that is expressed specifically in the developing endosperm. We report the complete nucleotide sequence of a clone of one B-hordein gene (pBHR184). The cloned gene contains no introns and belongs to the B1 sub-family of B-hordein genes. Comparison of the 5'-flanking sequences of pBHR184 with those of related S-rich prolamin genes from wheat shows that several short sequences within 600 bp upstream of the translation initiation codon are strongly conserved. A sequence that is conserved at around -300 bp in the S-rich prolamins is also conserved at similar locations in genes encoding the two major classes of maize prolamin (the Z19 and Z21 zeins) and appears to be unique to prolamin genes. We discuss the possible role of this '-300 element' in the control of gene expression in the developing cereal endosperm.

Inhibition of gibberellin biosynthesis by paclobutrazol in cell-free homogenates of Cucurbita maxima endosperm and Malus pumila embryos

Abstract: The plant growth retardant paclobutrazol, (PP333) (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol, inhibits specifically the three steps in the oxidation of the gibberellin-precursorent-kaurene toent-kaurenoic acid in a cell-free system fromCucurbita maxima endosperm. The KI50 for this inhibition is 2×10−8 M. The KI50 values for the separated2S, 3S, and2R, 3R enantiomers of paclobutrazol in this system are 2×10−8 M and 7×10−7 M, respectively. A cell-free preparation from immatureMalus pumila embryos convertsent-kaurene to gibberellin A9, whereas no conversion occurs in a similar preparation fromMalus endosperm. The conversion ofent-kaurene by the embryo preparation is inhibited by paclobutrazol with KI50 values for the2S,3S and2R,3R enantiomers of 2×10−8 M and 6×10−8 M, respectively.

Effect of environmental temperature at the milky stage on amylose content and fine structure of amylopectin of waxy and nonwaxy endosperm starches of rice (Oryza sativa L.).

Abstract: Starch granules were isolated from polished grains of rice plants (Oryza sativa L.), waxy and nonwaxy near-isogenic lines of a Japonica rice cultivar, Taichung 65, grown under controlled temperature conditions. Amylose contents and distributions of β-1,4 chains of amylopectin, and further details of the fine structure of waxy amylopectin were determined by enzymatic and chromatographic methods. The higher environmental temperature decreased amylose contents in endosperm starches of nonwaxy rice plants. Moreover, the higher environmental temperature increased the amount of long B chains of amylopectin and decreased mainly that of short B chains and slightly that of a chains as compared with the lower environmental temperature.

DNA amplification patterns in maize endosperm nuclei during kernel development

Abstract: Increased DNA levels in centrally located endosperm nuclei are shown to be related to endosperm development in Zea mays. Mitotic activity sharply decreases in endosperm cells 10-12 days after pollination. At this time nuclear size and DNA content per nucleus (where C = haploid content) sharply increase until peak levels are reached at about 14-18 days after pollination. Mean DNA content per endosperm nucleus in strain A188 was shown by Feulgen cytophotometry to increase to about 90C by this peak stage, with the pattern being remarkably consistent over four consecutive growing seasons. Some individual nuclei achieved levels of >200C. Most other strains compared during one growing season averaged even higher peak levels of DNA per nucleus than did A188. Individual nuclei in those strains reached levels as high as 690C. A decrease in DNA level was observed in older endosperms with most strains. Endosperm mutant strains did not show a significant reduction in DNA. Opaque-2 mutants in several backgrounds achieved higher levels of DNA per nucleus. DNA levels from F1 endosperms did not indicate heterosis. Regardless of differences in DNA content, the pattern of DNA increasing as development proceeds followed by a DNA decrease was observed for most strains. Cytological studies reveal much variation in chromatin strandedness, a maximum of three nucleoli, a maximum of three nucleolar organizer regions, and ≈30 diffuse chromatin masses in older endosperm tissue. A form of DNA amplification, perhaps polytenization, appears to be occurring during endosperm development.

Thermal Environment During Endosperm Cell Division in Maize: Effects on Number of Endosperm Cells and Starch Granules1

Abstract: Reductions in kernel mass are observed when corn (Zea mays L.) kernels are grown in vitro or when unfavorable temperature occurs during endosperm cell division. We investigated the possibility that a decreased number of endosperm cells or a decreased number of starch granules is responsible for the reduced kernel mass in such environments. Three-day-old kernels of the single cross hybrid A619 ✕ W64A were placed in culture on a denned medium at 15, 30, and 35 °C, and their growth was compared with kernels from ears developed in the field or greenhouse. Kernels cultured at 30°C attained a final mass of 164 mg compared with 274 mg for field-grown controls. At 30°C, endosperm cell division ceased approximately 10 days earlier, and the final number of cells was reduced by 34%. Final kernel mass was reduced by 49 and 78% when kernels were cultured at 15 and 35°C, respectively, compared with those grown at 30°C. At 35°C, the rate and duration of cell division in the endosperm, and the number of endosperm cells were severely reduced. In contrast, the rate of cell division decreased in kernels cultured at 15°C, but the duration was prolonged, and the number of endosperm cells formed was not affected. However, the number of starch granules initiated at 15 and 35°C was reduced by 70 and 97%, respectively. Final kernel mass was highly correlated with the number of endosperm cells (r=0.85,p≤0.01) and starch granules formed (r=0.76, p≤0.01). These data suggest that thermal regulation of the number of endosperm cells, starch granules, or both are mechanisms by which final kernel mass may be mediated. The reduction in mass of in vitro compared with field- or greenhouse-grown kernels appears to be due mainly to a decline in the number of endosperm cells formed.

The Role of Maturation Drying in the Transition from Seed Development to Germination

Abstract: Kermode, A. R., Gilford, D. J. and Bewley, J. D. 1985. The role of maturation drying in the transition from seed development to germination. III. Insoluble protein synthetic pattern changes within the endosperm of Ricinus communis L. seeds.—J. exp. Bot. 36: 1928-1936. Immature seeds of Ricinus communis L. cv. Hale (castor bean) removed from the capsule at 30 or 40 days after pollination (DAP) can be induced to germinate by being subjected to drying. This desiccation-induced switch from development to germination is mirrored by a change, upon subsequent rehydration, in the pattern of insoluble protein synthesis within the endosperm storage tissue. During normal development from 25-40 DAP there is rapid synthesis of the insoluble (1 IS) crystalloid storage protein. At later stages of development (45 and 50 DAP), crystalloid protein synthesis declines markedly and synthesis of new insoluble proteins commences. Following premature drying at 30 or 40 DAP, the pattern of insoluble protein synthesis upon rehydration is virtually identical to that following imbibition of the mature seed. Proteins synthesized during normal late development (at 45 and 50 DAP) are produced up to 48 h after imbibition; a subsequent change in the pattern of insoluble protein synthesis occurs between 48 and 72 h. Thus, in contrast to the rapid switch in the pattern of soluble protein synthesis induced by drying, insoluble protein syntheses within the endosperm are redirected towards those uniquely associated with a germination/growth programme only after a considerable delay following mature seed imbibition, or following rehydration of the prematurely dried seed. Nevertheless, these results support our contention that drying plays a role in the suppression of the developmental metabolic programme and in the permanent induction of a germination/growth programme.

High amylose mutants of rice,Oryza sativa L.

Abstract: Five mutant lines of rice with increased amylose content in starch granules were identified among floury endosperm mutants. The amylose contents of the mutants ranged from 29.4% to 35.4% and were about twice as high as that of the normal counterpart. Starch properties of the high amylose mutants were analyzed by column chromatography, X-ray diffractometry, photopastegraphy and scanning electron microscopy. The high amylose mutants produced longer unit chains of amylopectin than those of the normal counterpart as well as an increased amount of amylose. A X-ray diffractogram of starch in the mutant was characterized by a type B pattern, while that in the normal counterpart showed a type A pattern which is typical for starches of common cereals. The temperatures at the initiation of gelatinization of the mutants were much higher than that for the normal counterpart. The endosperm cells of the mutant were loosely packed with irregular round-shaped starch granules, whereas those of the normal counterpart were densely packed with polyhedral starch granules. Judging from the results obtained, it was concluded that starch properties of the high amylose mutants of rice were similar to those of the amylose-extender (ae) mutant of maize.

Correct targeting of the bean storage protein phaseolin in the seeds of transformed tobacco.

Abstract: The storage protein phaseolin accumulates during seed development in protein bodies in cotyledons of the common bean Phaseolus vulgaris. Hall et al. (In L Van Vloten-Doting, TC Hall, eds, Molecular Form and Function of the Plant Genome, 1985 Plenum Press, In press) recently reported the expression of a gene coding for phaseolin and the accumulation of phaseolin protein in developing seeds of tobacco plants regenerated from transformed callus cells. The protein did not accumulate in other organs of the plants. Mature seeds from normal and transformed tobacco plants were obtained and the subcellular distribution of phaseolin in the seeds was examined using both light and electron microscopic immunocytochemical methods. Phaseolin was found in six of seven transformed tobacco embryos examined, but was present in only one endosperm of five. When present, phaseolin was located exclusively in the protein bodies of the embryonic and endospermic cells. Furthermore, phaseolin was restricted solely to the amorphous matrix of the protein bodies and was excluded from the globoid and proteinaceous crystalloid components of these organelles. The subcellular location of phaseolin in seeds from transformed tobacco plants is similar to that seen in mature seeds of the common bean indicating that in the transformed cells the protein is targeted to the right subcellular compartment.

Organic free radical levels in seeds and pollen: The effects of hydration and aging

Abstract: In view of their possible role in oxidative deterioration of seeds and pollen, organic free radicals were measured by electron spin resonance in embryonic axes and cotyledons of soybean [Glycine max (L.) Merr], embryo and endosperm fractions of corn [Zea mays L.] and pollen of cattail [Typha latifolia L.]. A pronounced decline in the radical signal ensued when hydration increased above about 7% (wet weight basis) in both the seed materials and in pollen. Moderate hydration of the soybean axis followed by drying led to a small decrease in organic free radicals compared to untreated material, especially if the desiccation step was performed under nitrogen. In a comparison of soybeans of various ages under normal storage, organic free radical levels in the axis showed little or no increase with age. In marked contrast, over 5 days of accelerated aging at 40°C and near-saturating humidity, organic radical levels approximately doubled in the axis. This pronounced increase in free radical content was not associated with a decrease in the proportion of polyunsaturated fatty acids. The data suggest that hydration of seed and pollen causes a release of free radicals from the trapped state.

Anatomy of immature grains of eight maternal effect shrunken endosperm barley mutants

Abstract: The anatomical basis for the shrunken endosperm phenotype of eight recessive maternal effect mutants (segl-seg8) of barley (Hordeum valgare L.) is described. Plants which are homozygous recessive for these nuclear genes produce only shrunken seeds regardless of pollen source. Light microscopy revealed that four of the mutants, segl, seg3, seg6, and seg7, exhibited premature termination of grain filling because of the necrosis and crushing of the chalaza and nucellar projection of the pericarp early in the grain-filling period, resulting in thin, wrinkled seed. Endosperm growth of these mutants before the occurrence of chalazal necrosis seemed normal. The other four mutants exhibited characteristic abnormalities in the endosperm growth pattern but normal development of maternal-origin tissues. Endosperm size was severely reduced in seg2, in which two flat columns of tissue were present with no central endosperm. Seg4 and seg5 developed distorted, disorganized endosperms of variable size. Endosperms of seg8 developed as two well-filled lobes with no central endosperm, resulting in a distinct dorsal crease. We suggest that the mutants are useful as probes to study maternal effects on endosperm development. THERE EXISTS a series of eight maternal effect, spontaneous, shrunken endosperm mutants of barley (Hordeum vulgare L.) designated seglseg8 which has been studied genetically but without reference to the detailed anatomy of the phenotypes (Jarvi and Eslick, 1975; Ra

Genetic control of endosperm proteins in wheat : 3. Allocation to chromosomes and differential expression of high molecular weight glutenin and gliadin genes in intervarietal substitution lines of common wheat.

Abstract: Total endosperm proteins extracted from both several common wheat cultivars and some intervarietal substitution lines derived from them were fractionated according to their molecular weight in a high resolution one-dimensional gel electrophoresis. The four donor cultivars and the recipient one - 'Chinese Spring', possessed differentially migrating protein bands in the fractions of high molecular weight (HMW) glutenins and gliadins. Several of these bands were identified for the first time in this study. By utilizing intervarietal substitution lines the control of the HMW glutenins and gliadins by chromosomes of homoeologous group 1 was either reaffirmed or, for the new bands, established. Several HMW gliadin subunits showed a considerable variation in their staining intensity in the intervarietal substitution lines indicating that their expression was dependent on the genetic background.

The Role of Maturation Drying in the Transition from Seed Development to GerminationIII. INSOLUBLE PROTEIN SYNTHETIC PATTERN CHANGES WITHIN THE ENDOSPERM OF Ricinus communis L. SEEDS

Abstract: Kermode, A. R., Gilford, D. J. and Bewley, J. D. 1985. The role of maturation drying in the transition from seed development to germination. III. Insoluble protein synthetic pattern changes within the endosperm of Ricinus communis L. seeds.—J. exp. Bot. 36: 1928-1936. Immature seeds of Ricinus communis L. cv. Hale (castor bean) removed from the capsule at 30 or 40 days after pollination (DAP) can be induced to germinate by being subjected to drying. This desiccation-induced switch from development to germination is mirrored by a change, upon subsequent rehydration, in the pattern of insoluble protein synthesis within the endosperm storage tissue. During normal development from 25-40 DAP there is rapid synthesis of the insoluble (1 IS) crystalloid storage protein. At later stages of development (45 and 50 DAP), crystalloid protein synthesis declines markedly and synthesis of new insoluble proteins commences. Following premature drying at 30 or 40 DAP, the pattern of insoluble protein synthesis upon rehydration is virtually identical to that following imbibition of the mature seed. Proteins synthesized during normal late development (at 45 and 50 DAP) are produced up to 48 h after imbibition; a subsequent change in the pattern of insoluble protein synthesis occurs between 48 and 72 h. Thus, in contrast to the rapid switch in the pattern of soluble protein synthesis induced by drying, insoluble protein syntheses within the endosperm are redirected towards those uniquely associated with a germination/growth programme only after a considerable delay following mature seed imbibition, or following rehydration of the prematurely dried seed. Nevertheless, these results support our contention that drying plays a role in the suppression of the developmental metabolic programme and in the permanent induction of a germination/growth programme.

Enzyme Activities of Starch and Sucrose Pathways and Growth of Apical and Basal Maize Kernels

Abstract: Apical kernels of maize (Zea mays L.) ears have smaller size and lower growth rates than basal kernels. To improve our understanding of this difference, the developmental patterns of starch-synthesis-pathway enzyme activities and accumulation of sugars and starch was determined in apical- and basal-kernel endosperm of greenhouse-grown maize (cultivar Cornell 175) plants. Plants were synchronously pollinated, kernels were sampled from apical and basal ear positions throughout kernel development, and enzyme activities were measured in crude preparations. Several factors were correlated with the higher dry matter accumulation rate and larger mature kernel size of basal-kernel endosperm. During the period of cell expansion (7 to 19 days after pollination), the activity of insoluble (acid) invertase and sucose concentration in endosperm of basal kernels exceeded that in apical kernels. Soluble (alkaline) invertase was also high during this stage but was the same in endosperm of basal and apical kernels, while glucose concentration was higher in apical-kernel endosperm. During the period of maximal starch synthesis, the activities of sucrose synthase, ADP-Glc-pyrophosphorylase, and insoluble (granule-bound) ADP-Glc-starch synthase were higher in endosperm of basal than apical kernels. Soluble ADP-Glc-starch synthase, which was maximal during the early stage before starch accumulated, was the same in endosperm from apical and basal kernels. It appeared that differences in metabolic potential between apical and basal kernels were established at an early stage in kernel development.

Developmental Changes in the Structure of Endosperm Starch of Rice (Oryza sativa L.)

Abstract: The developmental changes in the structure and properties of endosperm starches were investigated using the near-isogenic lines for wx alleles of rice. The amylose content in nonwaxy starch was increased during the development of rice grains. Because the accumulation of amylose in endosperm stopped earlier than that of amylopectin during development, the percentages of amylose reached a maximum at the 17th day after flowering in nonwaxy endosperm. Since the distributions of the unit-chain length of amylopectin in waxy and nonwaxy starches were unchanged with the development of the grains, these amylopectins would be synthesized in a similar manner through development. The structure and properties of endosperm starches were reconfirmed to be conspicuously affected by the temperature at the early developmental stages of the grain-filling period, namely, they appeared to be characterized by the temperature at which the starch was accumulated in the endosperm.

Synthesis and intracellular transport of lectin and storage protein precursors in endosperm from castor bean

Abstract: The biosynthesis of the lectins and the other major storage proteins, the 11S globulins and the 2S albumins, which are found in protein bodies has been studied in developing castor bean endosperm cells. Newly synthesized proteins were radiolabelled by incubating intact endosperm tissue with [35S]methionine. The intracellular distribution of radiolabelled proteins was determined after fractionating endosperm homogenates by sucrose density gradient centrifugation. Pulse-chase experiments revealed that all the major protein body components are initially segregated in precursor form into the lumen of the endoplasmic reticulum. The lectin precursors appeared as a group of 64000–68000-Mr glycosylated polypeptides, the 11S globulins as a group of 46000–55000-Mr polypeptides and the 2S albumins as a single 32500-Mr polypeptide. These precursors were transferred from the endoplasmic reticulum to a population of transporting vesicles. The subsequent disappearance of the precursors from this vesicle fraction was accompanied by the accumulation of mature polypeptides in the protein body matrix (lectins and 2S albumins) or in the insoluble protein body crystalloid complexes (11S globulins). The castor bean proteins studied all exist as heterodimers in the protein bodies. After intracellular transport an endoproteolytic step is required to release each subunit of the heterodimer from the appropriate single polypeptide precursor.

Synthesis and Degradation of Fructose 2,6-Bisphosphate in Endosperm of Castor Bean Seedlings

Abstract: The aim of this work was to examine the possibility that fructose 2,6-bisphosphate (Fru-2,6-P2) plays a role in the regulation of gluconeogenesis from fat. Fru-2,6-P2 is known to inhibit cytoplasmic fructose 1,6-bisphosphatase and stimulate pyrophosphate:fructose 6-phosphate phosphotransferase from the endosperm of seedlings of castor bean (Ricinus communis). Fru-2,6-P2 was present throughout the seven-day period in amounts from 30 to 200 picomoles per endosperm. Inhibition of gluconeogenesis by anoxia or treatment with 3-mercaptopicolinic acid doubled the amount of Fru-2,6-P2 in detached endosperm. The maximum activities of fructose 6-phosphate,2-kinase and fructose 2,6-bisphosphatase (enzymes that synthesize and degrade Fru-2,6-P2, respectively) were sufficient to account for the highest observed rates of Fru-2,6-P2 metabolism. Fructose 6-phosphate,2-kinase exhibited sigmoid kinetics with respect to fructose 6-phosphate. These kinetics became hyperbolic in the presence of inorganic phosphate, which also relieved a strong inhibition of the enzyme by 3-phosphoglycerate. Fructose 2,6-bisphosphatase was inhibited by both phosphate and fructose 6-phosphate, the products of the reaction. The properties of the two enzymes suggest that in vivo the amounts of fructose-6-phosphate, 3-phosphoglycerate, and phosphate could each contribute to the control of Fru-2,6-P2 level. Variation in the level of Fru-2,6-P2 in response to changes in the levels of these metabolites is considered to be important in regulating flux between fructose 1,6-bisphosphate and fructose 6-phosphate during germination.

Fatty acid synthesis in the oil palm (Elaeis guineensis): incorporation of acetate by tissue slices of the developing fruit

Abstract: Oil palm (E. guineensis) fruits at three stages of development were studied. At week 12–13 after anthesis, the endosperm had started accumulating oil and tissue slices incorporated [1-14C] acetate into fatty acids which resembled those found in the mature endosperm. The mesocarp contained very little oil and incorporated acetate into polar lipids. At week 16–17, the mesocarp started to accumulate oil; this was reflected in the [14C] lipid products from acetate incubation. At or just prior to this stage, an increase in the endogenous linoleic and linolenic acid content and the increase in fruit size indicated cellular growth in the mesocarp tissue. At week 20–21 the fruit was ripe, and both endosperm and mesocarp tissues were filled with storage oil. [14C] Fatty acids synthesized from acetate by mesocarp slices at this stage were the same as the endogenous storage fatty acids in bothE. guineensis andE. oleifera. A very weak fatty acid synthesizing activity was seen in the mature endosperm, but the products had no relationship to the storage lipid.

Effect of Increased Temperature in Apical Regions of Maize Ears on Starch-Synthesis Enzymes and Accumulation of Sugars and Starch

Abstract: Apical florets of maize (Zea mays L) ears differentiate later than basal florets and form kernels which have lower dry matter accumulation rates The purpose of this study was to determine whether increasing the temperature of apical kernels during the dry matter accumulation period would alter the difference in growth rate between apical and basal kernels Apical regions of field-grown maize (cultivar Cornell 175) ears were heated to 25 ± 3°C from 7 days after pollination to maturity (tip-heated ears) and compared with unheated ears (control) In controls, apical-kernel endosperm had 24% smaller dry weight at maturity, lower concentration of sucrose, and lower activity of ADP-Glc starch synthase than basal-kernel endosperm, whereas ADP-Glc-pyrophosphorylase (ADPG-PPase) activities were similar In tip-heated ears apical-kernel endosperm had the same growth rate and final weight as basal-kernel endosperm and apical kernels had higher sucrose concentrations, higher ADP-Glc starch synthase activity, and similar ADPG-PPase activity Total grain weight per ear was not increased by tip-heating because the increase in size of apical kernels was partially offset by a slight decrease in size of the basal- and middle-position kernels Tip-heating hastened some of the developmental events in apical kernels ADPG-PPase and ADP-Glc starch synthase activities reached peak levels and starch concentration began rising earlier in apical kernels However, tip-heating did not shorten the period of starch accumulation in apical kernels The results indicate that the lower growth rate and smaller size of apical kernels are not solely determined by differences in prepollination floret development

Isolation of Amyloplasts from Developing Maize Endosperm

Abstract: Methods for the formation of protoplasts from developing maize endosperm and for the aqueous isolation of intact amyloplasts from such protoplasts are described. Protoplasts were obtained after incubating endosperm slices in a medium containing cellulase and pectolyase for 5 days at 4°C or 5 hours at 30°C. After purification in a Ficoll density gradient, the protoplasts were reptured by forcing the suspension through a Nitex mesh (20 micrometer) positioned at the lower end of a modified disposable syringe. The resulting filtrate was layered on a discontinuous Ficoll density gradient of 30, 15, and 10%. Each Ficoll solution contained 0.7 molar sucrose, 10 millimolar arginine, 10 millimolar dl-dithiothreitol, 50 millimolar 2-(N-morpholino)ethanesulfonic acid (pH 5.6), and 2 millimolar CaCl2. After 3 hours in the cold, an amyloplast fraction 50 to 93% intact and free from cytoplasmic, mitochondrial, and glyoxysomal contamination was recovered in the 15% Ficoll layer. Amyloplast intactness was estimated by fluorescent microscopy and activity of certain amyloplast marker enzymes before and after rupture of the amyloplast membrane. Starch branching enzyme, ADPG-pyrophosphorylase, and nitrite reductase were used as amyloplast marker enzymes.

The interaction of endosperm genotype and genetic background. Part I. Differences in chromatographic profiles of starches from nonmutant and mutant endosperms

Abstract: Comparaison des profils d'elution par filtration sur gel d'amidon de mais normaux, de 4 mutants et de combinaisons simples, doubles ou triples entre ces mutants. Effet sur la composition des amidons et leurs proprietes

Molecular Species of Ceramide and Mono-, Di-, Tri-, and Tetraglycosylceramide in Bran and Endosperm of Rice Grains

Abstract: Ceramide and mono-, di-, tri-, and tetraglycosylceramide were isolated from the bran and endosperm of rice grains and chemically characterized. The detailed compositions of free ceramide were somewhat different between the bran and endosperm, but those of the ceramide moiety in glycosylceramides were substantially the same. There was a tendency in all the sphingolipid molecules in rice grains for hydroxy acids with C20 to be combined largely with the dihydroxy bases while hydroxy acids with C24< combined mainly with the trihydroxy bases. Representative molecular species of the sphingolipid classes were concluded to be as follows: for ceramide N-2'-hydroxylignoceroyl-4-hydroxysphinganine, for monoglycosylceramide 1-O-β-glucosyl-N-2'-hydroxyarachidoyl-4, 8-sphingadienine, for diglycosylceramide 1-O-[β-mannosyl(1→4)-O-β-glucosyl] and 1-O-β-glucosyl(→4)-O-β-glucosyl]-N-2'-hydroxylignoceroyl-4-riydroxy-8-sphingenine, for triglycosylceramide 1-O-[β-mannosyl(1→4)-O-β-mannosyl(1→4)-O-β-glucosyl]- and 1-O-[β-glucosyl(1→4)-O-β-mannosyl(1→)-O-β-glucosyl]-N-2'-hydroxylignoceroyl-4-hydroxy-8-sphingenine, and for tetraglycosylceramide 1-O-[β-mannosyl(1→4))-O-β-mannosyl (1→)-O-β-mannosyl(1→4)-O-β-glucosyl]- and 1-O-[β-glucosyl(1→4)-O-β-mannosyl(1→4)-O-βmannosyl(1→4)-O-β-glucosyl]-N-2'-hydroxylignoceroyl-4-riydroxy-8-sphingenine.

Structure and biochemistry of endosperm breakdown in date palm (Phoenix dactylifera L.) seeds

Abstract: The zone of endosperm breakdown in the germinated date seed (Phoenix dactylifera L.) is a narrow area immediately adjacent to the surface of the enlarging cotyledon, or haustorium. The zone width is correlated with the amount of cell division in the adjacent region of the haustorium. The sequence of endosperm breakdown is: 1. protein bodies vacuolate, 2. storage cell walls become electron-transparent immediately adjacent to the protoplast of each endosperm cell, 3. all remaining cytoplasm and lipid bodies disappear, and 4. the remaining cell walls become electron-transparent and collapse against the haustorium surface. Two cell wall hydrolases are present—endo-Βmannanase (EC3.2.1.78) and Β-mannosidase (EC3.2.1.25). Β-mannosidase is detectable in the endosperm before germination. At germination, the major portion of activity is found in the softened endosperm. Β-mannanase is only detectable from germination and there is always hundreds of fold greater activity in the softened endosperm than elsewhere. Proteinase is detectable in trace amounts at germination in the softened endosperm but is also found in the haustorium at later stages. Isolated haustoria, incubated in extracted ivory nut (Phytelephas macrocarpa) mannan in buffer, cause no mannan breakdown. Haustoria, incubated in a solution of locust bean galactomannan, cause no decrease in galactomannan viscosity. Our observations suggest that although haustoria probably regulate mannan breakdown in the endosperm, they do not seem to secrete the hydrolytic enzymes concerned.