The pentacyclic triterpene Esters and the free,esterified and glycosylated sterols of Sorghum vulgare grain

The free, esterified and glycosylated sterols and triterpene esters of Sorghum vulgare grains were analysed by GLC. 4-Demethylsterols were found free, esterified and glycosidated. 4-Monomethyl-sterols were found completely free whilst the triterpenes were completely esterified. Three quarters of the total sterols in the grain were located in the embryo whilst the triterpenes were equally distributed between the embryo and endosperm.     

A sulfonolipid and novel glucosamidyl glycolipids from the extreme thermoacidophile Bacillus acidocaldarius.

The total lipid content of the extreme thermoacidophile Bacillus acidocaldarius comprises about 8.1% of the cell dry weight. Total lipid had a distribution of 15.7% neutral linique component initially characterized as an N-acylglucosamine beta-linked to the primary hydroxyl of an unusual fully saturated pentacyclic triterpene derived tetrol(C35H62O4, Mr 546), which appears to be a derivative of the pentacylcic triterpene hopane substituted at C-29 with a 1,2,3,4-tetrahydroxy pentane. Other major glycolipids present were partially characterized as O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta D-glucopyranosyldiacylglycerol and O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylmonoacylglycerol. Minor components of the glycolipid fraction included O-beta-D-glucopyranosyl-(1 leads to 4)-O-2-acylamido-2-deoxy-beta-D-glucopyranosylglycerol, O-2-amino-2-deoxy-beta-D-glucopyranosyl pentacyclic tetrol and free pentacyclic tetrol. The distributions of esterified and amide-linked fatty acids were similar, being comprised primarily of branched heptadecanoic, 11-cyclohexyundecanoic and 13-cyclohexyltridecanoic acids. The acid lipids were composed of a sulfonoglycosyldiacylglycerol (43.2%), diphosphatidylglycerol (32.3%), lysodiphosphatidylglycerol (5.3%), phosphatidic acid (5.8%) and phosphatidylglycerol (13.4%).     

Gibberellin-like substances and indole type auxins in developing grains of normal- and high-lysine genotypes of barley

Changes in gibberellin-like activity and content of indole type auxins were investigated during grain development of the two high-lysine barley (Hordeum vulgare L.) genotypes Sv 73608 and Risø 1508, and their corresponding normal cultivars Mona and Bomi. A peak in gibberellin-like activity was found in developing grains of the normal cultivars about 18 days after anthesis, whereas the grains of the high-lysine genotypes showed a two to five times higher maximum about 3–4 days later. The auxin content of the cultivar Bomi showed a maximum between the 22nd and the 29th day after anthesis, whereas, throughout their development the grains of the mutant Risø 1508 exhibited only about ¹/10 of the maximum level of auxin found in the grains of Bomi. The normal cultivar Mona also displayed higher contents of auxin than the high-lysine genotypes Sv 73608, particularly at the later stages of grain growth, but the differences in concentration were considerable smaller than for the pair ‘Bomi’—‘Risø 1508’. It is suggested that auxins play an important role in the development of barley grains.     

Changes in Amide-Linked and Ester Indole-3-Acetic Acid in Cotton Fruiting Forms during Their Development

The concentration of free indoleacetic acid (IAA) is high in cotton (Gossypium hirsutum L.) fruiting forms before anthesis, but is low at and for a few days after anthesis. Amide-linked and ester IAA were measured in fruiting forms at 9, 6, and 3 days before anthesis; at anthesis; and at 2, 4, 7, and 9 days after anthesis to determine if free IAA decreased because it was converted to a conjugated form. That did not appear to be the case. While the major decrease in free IAA occurred during the 6 days before anthesis, ester IAA increased only a small amount and amide-linked IAA decreased even more than free IAA. During the 6 days before anthesis free IAA decreased from 0.62 to 0.12 micrograms per gram and amide-linked IAA decreased from 19.14 to 1.16 micrograms per gram dry weight. No evidence was found that a large amount of amide-linked IAA was converted to an insoluble form; flowers contained less than 1 microgram per gram of insoluble IAA. The free and amide-linked IAA must have been converted to other forms, perhaps by oxidation. Soluble amide-linked IAA remained low after anthesis. No ester IAA was detected 6 days before anthesis and only 0.08 microgram per gram dry weight was measured at anthesis. The concentration of ester IAA increased thereafter to 4.43 micrograms per gram at 9 days after anthesis. Therefore, amide-linked IAA was the major form of IAA in flower buds and ester IAA was the major form in young fruits (bolls). Minimum concentrations of free and total IAA occurred during the 4 days after anthesis, a stage when cotton fruiting forms are most likely to abscise. The large decreases in free and amide-linked IAA during the 6 days before anthesis may indicate a rapid turnover of IAA in flower buds. But, the decrease in free IAA was not accompanied by a comparable increase in ester or amide-linked IAA.     

Phosphofructokinase from immature wheat grains

Levels of phosphofructokinase and metabolites known to affect its activity were monitored at different stages of wheat grain development. Phosphofructokinase activity peaked at 28 days after anthesis, declining thereafter. The amount of citrate increased up to 14 days after anthesis. PEP, ATP, ADP and AMP showed peak values at 28 days after anthesis. Phosphofructokinase from 28-day-old grains was purified × 23 with 49% recovery by ammonium sulphate fractionation and chromatography on DEAE-Sephadex A-50. A normal hyperbolic curve was observed with F-6-P. ATP inhibited the enzyme above 0.75 mM. ADP, citrate and 2-P-glycolate inhibited the enzyme noncooperatively; K_i values being 2.2, 1.6 and 5.0 mM, respectively. PEP and AMP failed to inhibit the enzyme activity     

C]Sucrose Uptake and Labeling of Starch in Developing Grains of Normal and segl Barley

Previous work showed that the segl mutant of barley (Hordeum vulgare cv Betzes) did not differ from normal Betzes in plant growth, photosynthesis, or fertility, but it produced only shrunken seeds regardless of pollen source. To determine whether defects in sucrose uptake or starch synthesis resulted in the shrunken condition, developing grains of Betzes and segl were cultured in [¹⁴C]sucrose solutions after slicing transversely to expose the endosperm cavity and free space. In both young grains (before genotypes differed in dry weight) and older grains (17 days after anthesis, when segl grains were smaller than Betzes), sucrose uptake and starch synthesis were similar in both genotypes on a dry weight basis. To determine if sucrose was hydrolyzed during uptake, spikes of Betzes and segl were allowed to take up [fructose-U-¹⁴C]sucrose 14 days after anthesis and the radioactivity of endosperm sugars was examined during 3 hours of incubation. Whereas less total radioactivity entered the endosperm and the endosperm cavity (free space) of segl, in both genotypes over 96% of the label of endosperm sugars was in sucrose, and there was no apparent initial or progressive randomization of label among hexose moieties of sucrose as compared to the free space sampled after 1 hour of incubation. We conclude that segl endosperms are capable of normal sucrose uptake and starch synthesis and that hydrolysis of sucrose is not required for uptake in either genotype. Evidence suggests abnormal development of grain tissue of maternal origin during growth of segl grains.     

Changes in Abscisic Acid and Indoleacetic Acid before and after Anthesis Relative to Changes in Abscission Rates of Cotton Fruiting Forms

Cotton (Gossypium hirsutum L.) fruiting forms exhibit pronounced changes, with age, in their probability of abscission. Large floral buds rarely abscise, but after anthesis the young fruits (bolls) have a high probability of abscising. Abscission rate reaches a peak about 5 to 6 days after anthesis and then gradually decreases. An experiment was conducted to try to determine the reason for the rapid and pronounced increase in probability of abscission just after anthesis. Cotton was grown in the field and fruiting forms of various ages from 9 days before to 9 days after anthesis were all harvested the same day and subsequently analyzed for ABA and IAA. The concentration of ABA decreased slightly at anthesis and increased gradually thereafter. In contrast, the concentration of IAA was high before anthesis and then decreased at anthesis to about one-fifth the previous concentration. IAA remained low for at least 4 days after anthesis and then increased rapidly between 7 and 9 days after anthesis. The high concentration of IAA in floral buds before anthesis is probably a major factor in their resistance to abscission. Likewise, the low concentration of IAA at anthesis and for about 4 days thereafter may promote fruit abscission during the young boll stage.     

Starch synthases and starch branching enzymes from Pisum sativum

Concentrations of ADPglucose:α-1,4-glucan-4-glucosyltransferase (starch synthase) and α-1,4 glucan: α-1,4-glucan-6-glycosyltransferase (branching enzyme) from developing seeds of Pisum sativum were measured. Primed starch synthase activity increased from 8 to 14 days after anthesis and decreased by 50 % at 26 days. Citrate-stimulated starch synthase activity was highest at 10 days after anthesis decreasing to low levels by 22 days. Branching enzyme activity increased from 8 to 18 days after anthesis and decreased little by 26 days. Two fractions of starch synthase were recovered by gradient elution from DEAE-cellulose of extracts from 12- and 18-day-old seeds. The two fractions differed in primer specificity, K_m for ADPG and relative amounts of citrate-stimulated activity. A major and minor fraction of branching enzyme were observed in extracts from both 12- and 18-day-old seeds. Marked differences in the relative abilities ofthe two branching enzyme fractions to stimulate phosphorylase and to branch amylose as well as pH optima were found. Although the content of the starch synthase and branching enzyme fractions varied with seed age, little difference was seen in the properties of chromatographically similar fractions. Therefore, the changes in starch synthase and branching enzyme activity during pea seed development resulted from changes in the concentrations of a few enzyme forms, but not the appearance of different enzyme forms.     

Effects of crop thinning and reduced grain numbers per ear on grain size in two winter wheat varieties given different amounts of nitrogen

To study the importance for final grain size in wheat (Triticum aestivum, L.) of assimilate supply and the storage capacity of the grain, two field experiments were done. In 1976 nitrogen was applied in the range from none to 180 kg ha^-1, part of the crop was thinned, and the top halves of some ears of the short variety Hobbit and of the tall variety Maris Huntsman were removed soon after anthesis. In 1977 ears of Maris Huntsman were halved 5 days after anthesis or at 30 days after anthesis when grain volume was maximum. Thinning the crop from 360 to 180 ear-bearing shoots m^-2 30 days before anthesis increased the number of grains per ear, except in the absence of nitrogen fertiliser, but did not increase grain size, grain dry weight per ear or total dry weight per culm. Removing the upper half of ears of Hobbit 5 days after anthesis increased dry weight per grain, but when this treatment was applied to Maris Huntsman either 5 days after anthesis in 1976 and 1977, or when grain volume was maximal in 1977, the grains failed to increase in dry weight. Non-grain dry weight of both varieties was increased by halving the ear. In both varieties the maximum volume of grains in halved ears was larger than in intact ears. Grain dry weight increased relatively less than volume after halving the ear of Hobbit, and the decrease in volume up to maturity was greater in halved than intact ears of both varieties. The larger grain volume in halved ears of Maris Huntsman in 1977 was associated with more endosperm cells.     

High throughput screening of mutants of oat that are defective in triterpene synthesis

The triterpenes are a large and diverse group of plant natural products that have important functions in plant protection and food quality, and a range of pharmaceutical and other applications. Like sterols, they are synthesised from mevalonate via the isoprenoid pathway, the two pathways diverging after 2,3-oxidosqualene. During triterpene synthesis 2,3-oxidosqualene is cyclised to one of a number of potential products, the most common of these being the pentacyclic triterpene β-amyrin. Plants often produce complex mixtures of conjugated triterpene glycosides which may be derived from a single triterpene skeleton. The delineation, functional analysis and exploitation of triterpene pathways in plants therefore represent a substantial challenge. Here we have carried out high throughput screening to identify mutants of diploid oat (Avena strigosa) that are blocked in the early steps of triterpene synthesis. We also show that mutants that are affected in the first committed step in synthesis of β-amyrin-derived triterpenes, and so are unable to cyclise 2,3-oxidosqualene to β-amyrin (sad1 mutants), accumulate elevated levels of primary sterols. The major differences were in Δ-7-campesterol and Δ-7-avenasterol, which both increased several fold relative to wild-type levels. This is presumably due to accumulation of squalene and 2,3-oxidosqualene and consequent feedback into the sterol pathway, and is consistent with previous reports in which specific oxidosqualene cyclase inhibitors and elicitors of triterpene biosynthesis were shown to have inverse effects on the flux through the sterol and triterpene pathways.     

Rabbit and human liver contain a novel pentacyclic triterpene ester with acyl-CoA: cholesterol acyltransferase inhibitory activity

Acyl-coenzyme A (CoA):cholesterol acyltransferase (ACAT) catalyzes the intracellular fatty acid esterification of cholesterol and is thought to play a key role in lipoprotein metabolism and atherogenesis. Herein we describe the purification and characterization of a novel pentacyclic triterpene ester from rabbit liver that has ACAT inhibitory activity. The inhibitor was purified by a combination of silicic acid chromatography and preparative thin layer chromatography. The compound inhibited both rabbit and rat liver microsomal ACAT activity with an IC50 = 20 microM. The lipid did not inhibit fatty acid incorporation into triglycerides, diglycerides, monoglycerides, or phospholipids nor did it inhibit plasma lecithin:cholesterol acyltransferase activity. However, rat liver microsomal acyl-CoA:retinol acyltransferase activity was inhibited by the terpene ester. Kinetic data are consistent with a mechanism in which ACAT is inhibited by the compound in an irreversible manner. The subcellular fractionation pattern of both ACAT activity and the ACAT inhibitor were similar in rabbit liver (both were approximately equally distributed in membranes that pelleted at 10,000 X g and 100,000 X g). A lipid with similar properties to the rabbit liver inhibitor was found in many other rabbit tissues, including adrenal and spleen, as well as in human liver. Rat liver did not contain this lipid. Structural analysis by NMR, mass spectrometry, and x-ray crystallography indicated that the rabbit liver inhibitor was a fatty acid ester (mostly stearate) of a pentacyclic triterpene acid. The carbon skeleton of the triterpene moiety is a new member of the olean-12-ene triterpene family. Both the negatively charged carboxylic acid group of the triterpene moiety and the esterified fatty acid group were necessary for the ACAT-inhibitory activity of the triterpene ester. Lastly, we present preliminary data which, together with the structural homology of the rabbit triterpene with known plant compounds, suggest the hypothesis that the triterpene moiety of the rabbit ACAT inhibitor arises from dietary absorption of a plant triterpene.     

牛奶子花粉形态特征与生活力测定

采用两种扫描电镜样品制备技术制备牛奶子花粉,扫描电镜观察其形态,研究结果表明:经自然干燥法制样,牛奶子花粉外观变形严重;采用固定—脱水制样,花粉外形保持良好,牛奶子花粉近球形,极面观钝三角圆形,具3沟,表面具脑纹状雕纹。采用I2-KI染色法测定牛奶子花粉开花后不同时间的生活力,结果表明:牛奶子花粉生活力在开花初较高,并在开花后36h内维持在80%以上,之后迅速下降,但在花期末仍有部分花粉具有生活力。     

Metabolism of free sugars in relation to starch synthesis in the developing Sorghum vulgare grain

Accumulation of starch at expense of its free-sugar precursors was studied in the developing grains of the ‘SL-44’variety of Sorghum vulgare Pers. The content of starch gradually increased with the maturation of the grain and this increase was relatively fast until 18 days after anthesis. The daily rate of starch accumulation was at a maximum 15 days after anthesis. The content of total free sugars, reducing sugars, non-reducing sugars other than sucrose, total and non-sucrosyl fructose, and glucose also increased, reaching maximum values at 18 days after anthesis. Sucrose content gradually increased with a concomitant decrease in the activity of invertase, and sucrose was the major non-reducing sugar in the matured grains. Detached heads incubated in labelled sugars indicated that, compared to sucrose and fructose. ¹⁴C was more efficiently incorporated from glucose into grain starch, which was maximally synthesized at the mid-milky stage of grain development. Exogenous supply of NAD⁺ plus ATP stimulated the in vivo incorporation of ¹⁴C from sucrose to starch. The decline in the rate of starch accumulation did not synchronise with that of protein synthesis.     

Pollen interception by linyphiid spiders in a corn agroecosystem: implications for dietary diversification and risk-assessment

Dietary diversification, including consumption of plant tissues such as pollen, can enhance the fecundity of generalist predators, resulting in improved control of pest prey. Supplemental pollen feeding has been observed in many natural enemies, including sheet-web spiders (Araneae: Linyphiidae), which represent a major component of food webs in agroecosystems. Their horizontal, ground-based webs have the potential to intercept pollen grains during anthesis of crop plants, providing the opportunity for consumption of pollen to occur. In laboratory feeding trials, Frontinella communis and Tennesseellum formicum (Araneae: Linyphiidae) readily fed on pollen grains dusted on their webs, with 82 and 92% of spiders consuming pollen within the 210 min trial. These results revealed a strong potential for dietary supplementation with pollen in ground-based sheet-web spiders, indicating that pollen feeding may be an important component of the feeding biology of linyphiids. To measure pollen and prey interception in simulated linyphiid webs, a 20 m × 20 m grid of miniature sticky traps was established within and downwind of a corn agroecosystem. Traps were exposed for 24 h, all intercepted material was transferred to the laboratory for subsequent identification, and replaced with additional traps for 28 consecutive days in July and August 2008, to encompass periods before, during and after anthesis. Over 150,000 corn pollen grains and 5,000 prey items (dominated by Collembola and Hemiptera) were intercepted at simulated web-sites. Dates of peak anthesis resulted in pollen counts as high as 4,000 grains per web-site in the interior of the cornfield. Spatial Analysis by Distance Indices (SADIE) indicated significant temporal and spatial variability in pollen interception within and outside the corn field, but interestingly there was no significant spatial association between pollen and prey. Furthermore, transgenic Bacillus thuringiensis corn expresses insecticidal proteins in pollen, posing an exposure risk to non-target arthropods. Consumption of corn pollen may be a route to transgenic protein exposure in this important taxon of generalist predators.     

Isoprenoids of Bacillus acidocaldarius

-The isoprenoids of Bacillus acidocaldarius, a notably acidophilic thermophilic organism, were investigated. Besides normal bacterial isoprenoids such as menaquinone and polyprenols, which latter were resolved in a-cis and a-trans fractions, and some minor components (a-tertiary-prenols and the corresponding anhydroderivatives), not fully characterized, and probably ‘natural’ artefacts, we have isolated and characterized squalene and pentacyclic triterpene hydrocarbons belonging to the hopane class, which must be accounted as unusual. Radioactivity from mevalonate-[2-¹⁴C] is incorporated into hopene-b (the major triterpene component), thus establishing the origin of cyclized squalene derivatives in B. acidocaldarius as a result of de novo synthesis.     

大麦胚和胚乳发育的相关性及贮藏营养物质的积累

大麦(Hordeum vulgare L.)开花后1d,见合子及退化助细胞,游离核胚乳尚未形成;开花后2～3d,胚为5及10个细胞,胚乳为游离核期;开花后4及5、6d,胚为梨形及长梨形,胚乳达细胞化期;开花后8d,胚为胚芽鞘期,糊粉层原始细胞产生;开花后10d,胚具1叶,糊粉层1～2层;开花后13d胚为2叶胚,亚糊粉层发生;开花后17d,3叶胚形成,糊粉层多为3层并停止分裂,菱柱形及不规则胚乳细胞分化;开花后21～29d,胚为4叶胚,胚乳进一步分化;开花后33d,胚为5叶成熟胚,胚乳亦成熟。淀粉、蛋白质在胚中积累始于开花后13d。在盾片中由基向顶发生,在胚芽鞘及叶原基中,首先在顶端出现。成熟盾片顶端的淀粉消失。开花后6d,胚乳开始积累淀粉;开花后10d,糊粉层及胚乳细胞积累蛋白质。开花17d后胚乳的蛋白质体多聚集,29d后蛋白质体显著减少。开花后17d,在盾片及糊粉层细胞中检测到油脂。果长或果长与稃片长之比和盾片长可作为不同发育期胚和胚乳的形态指标。     

Distribution of triterpene alcohols in subcellular fractions from Calendula officinalis flowers

The distribution of the triterpene mono- and dihydroxy alcohols was investigated in the subcellular fractions of the flowers of Calendula officinalis. The triterpene monols were found mainly in the chromoplast fraction (68% of total) with smaller amounts in the cell debris, microsomal and supernatant fractions, the mitochondrial fraction was almost devoid of these compounds. Triterpene diols were present exclusively in the chromoplast fraction, 98% in the form of the 3-monoesters and 2% in the form of diesters. It is suggested that the hydroxylation of the triterpene monols to the corresponding diols proceeds in the chromoplasts and the esterified form of the monols is probably the substrate for this reaction.     

Conjugated fatty acids from latex of Euphorbia lathyris

The fatty acids esterified with triterpene and diterpene alcohols from the latex of Euphorbia lathyris were analyzed. 77% of the fatty acids esterified with triterpenes were conjugated, the main components of which were decadienoic and decatrienoic acids. Of the acids esterified with diterpenes, 81% were decatrienoic and dodecatrienoic acids.     

Glut-5(10)-en-3-one from Andrachne cordifolia

Glut-5(10)-en-3-one, a new pentacyclic triterpene ketone, was isolated from Andrachne cordifolia (aerial parts roots).     

Separation and Some Properties of Large and Small Amyloplasts throughout Development in Barley Endosperm

A method is described whereby amyloplasts from immature barley (Hordeum distichum L.) endosperm could be separated into two populations of large and small amyloplasts at all stages of development. The small amyloplasts had more amylopectin than the large at early stages, but by 60 days after anthesis, the large had the greater proportion of amylopectin. Starch synthetase activity was associated with both types of amyloplast. The nucleotide specificity of the starch synthetase associated with each population varied independently throughout development. At 25 days after anthesis, the large amyloplasts were more susceptible than the small to α-amylolysis; however, at 38 and 60 days, the small amyloplasts became more susceptible.