Influence of Anaerobiosis on Chlorophyll Biosynthesis in Greening Oat Seedlings (Avena sativa L.)

The influence of anaerobiosis for 0.5 to 15 hours on the last steps of chlorophyll biosynthesis of etiolated oat seedlings was investigated. Phototransformation of protochlorophyllide to chlorophyllide is only slightly reduced and esterification of chlorophyllide is slightly increased by pretreatment under anaerobic conditions. Pretreated plants accumulate the geranylgeraniol ester of chlorophyllide rather than the phytol ester. Enzymic hydrogenation of the esterifying alcohol geranylgeraniol to phytol is presumably inhibited by anaerobiosis.     

Storage Protein Synthesis during Oat (Avena sativa L.) Seed Development

Oat (Avena sativa L.) seeds harvested at 2-day intervals from anthesis to maturity were tested for their ability to incorporate [³⁵S]sulfate into protein. Incorporation of [³⁵S]sulfate into TCA-insoluble material began 2 to 4 days postanthesis (DPA), reached a peak 14 to 16 DPA, and was barely detectable by 24 DPA. Incorporation of label into globulin was parallel to total protein accumulation, and averaged about 85% of the total protein synthesis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total protein extracted from developing seeds indicated that some polypeptides coinciding with the α and β globulin subunits were present 2 to 4 DPA, but the full complement of globulin polypeptides was not present until 10 DPA. Immunoprecipitation of in vivo labeled seed extracts showed that globulin polypeptides and the 59 kilodalton precursor were present at early stages of development (4 DPA). Quantitation of dot blot analysis, using an oat globulin cDNA clone as a probe, indicated that one species of oat globulin mRNA was most abundant 15 DPA, which is during the peak time of storage protein synthesis.     

Cell-free Synthesis of Globulin by Developing Oat (Avena sativa L.) Seeds

The primary storage protein synthesized during oat (Avena sativa L.) groat development is a globulin. Polysomes were isolated from oat groats 12 days after anthesis. These polysomes directed the incorporation of radioactive amino acids into protein in a cell-free protein synthesis system containing wheat germ supernatant. The Mg(2+) optimum was 4 mm, the pH optimum was 6-8, and the amount of amino acid incorporation depended on polysome concentration. Incorporation of amino acids was linear for about 10 min and approached a maximum after 20 min. Using the initiation inhibitor, T-2 toxin, it was determined that about 36% of the amino acid incorporation was due to the initiation of new polypeptide chains. The in vitro product co-electrophoresed with authentic oat groat globulin on polyacrylamide-sodium dodecyl sulfate (SDS) gels. The cyanogen bromide peptides of the in vitro product partially corresponded with those from authentic globulin when electrophoresed on polyacrylamide-SDS gels. These data suggest that the in vitro product is primarily oat globulin. The polysome population was separated into membrane-bound and free polysomes. Membrane-bound polysomes synthesized about twice the amount of protein as did free polysomes. Products synthesized in vitro on both types of polysomes were essentially the same.     

Uridine and the Control of Phototropism in Oat (Avena sativa L.) Coleoptiles

The short-term growth response of oat (Avena sativa L.) coleoptiles to exogenously applied uridine was studied both in excised apical segments and in the intact seedlings. In both cases growth of coleoptile tissue was inhibited by uridine. The inhibition of coleoptile growth consistently occurred 20–30 min after uridine treatment, which is within the lag period of their phototropic response. Asymmetric application of uridine to coleoptiles in the intact seedlings resulted in their bending toward the direction to which uridine was applied in the absence of light stimulus. These findings suggest that uridine or its metabolites, plays an important role in the phototropism of oat coleoptiles and provide support to the Bruinsma–Hasegawa theory as an alternative to the Cholodny–Went theory for explaining phototropism.     

The Localization of Oat (Avena sativa L.) Seed Globulins in Protein Bodies

The major storage proteins of the oat grain are the 12S and7S globulins. Using sodium dodecyl sulphate-polyacrylamide gelelectrophoresis (SDS-PAGE) and immuno-difTusion assays we havedemonstrated that the 7S globulin is localized predominantlyin the embryo and the 12S globulin chiefly in the endosperm.Protein bodies have been isolated using aqueous and non-aqueousmedia and sucrose density gradient ultracentrifugation. Assayingmarker enzymes gave results consistent with the presence ofvacuolar protein bodies in the preparations. SDS-PAGE of sequentialsalt and alcohol extractions demonstrated the presence of globulinsand prolamins respectively and their distribution within thegradient suggested that they may be localized in different proteinbodies. Key words: Avena sativa L., Seed globulins, Protein bodies, Localization.     

Protein Synthesis in Isolated Mitochondria of Rice (Oryza sativa L.) Seedlings

For studies of in organello mitochondrial protein synthesis in rice, Oryza sativa L., conventional surface-sterilization procedures were demonstrated to be ineffective. Because of the over-whelmingly efficient [³⁵S]methionine utilization by contaminating bacteria, even “essentially bacteria-free” rice mitochondria were shown to be unsuitable for the study of in organello protein synthesis. We developed a procedure to obtain a bacteria-free preparation of rice mitochondria. Such mitochondria favored a membrane-dependent ATP-generating system over an external ATP-generating system as the energy supplement for in organello protein synthesis. Two distinct classes of [³⁵S]methionine-labeled, cycloheximide-insensitive products were detected: an electrophoretically unresolved population and a set of some 22 to 27 discrete polypeptide species, each with a characteristic electrophoretic mobility and relative abundance.     

Chitinases and beta-1,3-Glucanases in the Apoplastic Compartment of Oat Leaves (Avena sativa L.)

To isolate chitinases and β-1,3-glucanases from the intercellular space of oats (Avena sativa L.), primary leaves were infiltrated with buffer and subjected to gentle centrifugation to obtain intercellular washing fluid (IWF). Approximately 5% of the chitinase and 10% of the β-1,3-glucanase activity of the whole leaf were released. Only small amounts (0.01-0.03%) of the intracellular marker malate-dehydrogenase were released into the IWF during infiltration. Activities of chitinase and β-1,3-glucanase in the IWF and in the leaf extract were compared by different chromatographic methods. On Sephadex G-75, chitinase appeared as a single peak (M_r 29.8 kD) both in IWF and homogenate. β-1,3-Glucanase, however, showed two peaks in the IWF (M_r 52 and 31.3 kD), whereas the elution pattern of the homogenate showed only one major peak at 22 kD. Chromatofocusing indicated that the IWF contained four chitinases and five β-1,3-glucanases. The elution pattern of the homogenate and IWF were similar with regard to the elution pH, but the peak intensities were distinctly different. Our results demonstrate that extracellular β-1,3-glucanases are different from those located intracellularly. Extracellular and intracellular chitinases do not differ in molecular properties, except for one isozyme which seems to be confined to the extracellular space. We suggest that both enzymes might play a special role in pathogenesis during fungal infection.     

Photoregulation of Phytochrome Synthesis in Germinating Embryos of Avena sativa L.

Hilton, J. R. and Thomas, B. 1987. Photoregulation of phytochromesynthesis in germinating embryos of Avena sativa L.—J.exp. Bot. 38: 1704–1712. The effect of light on the accumulation of phytochrome in germinatingAvena embryos was determined. A quantitative ELISA using monoclonalantibody AFRC MAC 56 was used to measure specifically type 1(or dark) phytochrome. A pulse of red light given after 14 himbibition but prior to the onset of type 1 phytochrome synthesis,strongly inhibited subsequent type 1 phytochrome accumulation.This effect of red light at 14 h was reversible by far-red lightindicating the involvement of phytochrome. Red light also inhibitedphytochrome synthesis after 18 h and 24 h imbibition but after24 h, far-red light did not reverse the effect. The effect ofred light treatment at 18 h was reversed by giving a pulse offar-red light at any time up to 30 h. Seed germination was notinfluenced by light under the conditions of these experiments.It is proposed that type 2 (or light) phytochrome may be responsiblefor photoregulation of type 1 phytochrome synthesis in germinatingAvena embryos. Key words: Photoregulation, phytochrome, seed.     

Site of Synthesis of the Enzymes of the Pyrimidine Biosynthetic Pathway in Oat (Avena sativa L.) Leaves

Heat-bleached oat (Avena sativa L. cv Porter) leaves lacking 70S chloroplast ribosomes have been used to demonstrate that four chloroplast-localized enzymes of pyrimidine nucleotide biosynthesis: aspartate carbamoyl-transferase, dihydroorotase, orotidine phosphoribosyl-transferase, and orotidine-5′-phosphate decarboxylase, are synthesized on cytoplasmic ribosomes. Two other chloroplast enzymes, carbamoyl phosphate synthetase, involved in both pyrimidine and arginine biosynthesis, and ornithine carbamoyltransferase, an enzyme of arginine biosynthesis, were also shown to be made on 80S ribosomes.     

Aluminum resistance mechanisms in oat (Avena sativa L.)

Background and aims

Enhanced aluminum (Al) resistance has been observed in dicots over-expressing enzymes involved in organic acid synthesis; however, this approach for improving Al resistance has not been investigated in monocots. Among the cereals, oat (Avena sativa L.) is considered to be Al resistant, but the basis of resistance is not known.

Methods

A hydroponic assay and hematoxylin staining for Al accumulation in roots were used to evaluate Al resistance in 15 oat cultivars. Malate and citrate release from roots was measured over a 24?h period. A malate dehydrogenase gene, neMDH, from alfalfa (Medicago sativa L.) was used to transform oat.

Results

Oat seedlings were highly resistant to Al, as a concentration of 325?μM AlK(SO₄)₂ was needed to cause a 50% decrease in root growth. Most oat cultivars tested are naturally resistant to high concentrations of Al and effectively excluded Al from roots. Al-dependent release of malate and Al-independent release of citrate was observed. Al resistance was enhanced in a transgenic oat line with the highest accumulation of neMDH protein. However, overall root growth of this line was reduced and expression of neMDH in transgenic oat did not enhance malate secretion.

Conclusions

Release of malate from oat roots was associated with Al resistance, which suggests that malate plays a role in Al resistance of oat. Over-expression of alfalfa neMDH enhanced Al resistance in some lines but was not effective alone for crop improvement.     

Sterols in seeds and leaves of oats (Avena sativa L.)

In seeds and leaves of oats (Avena sativa L.) 12 different sterols (cholesterol, cholstanol, ⁷-cholestenol, campesterol, campestanol, stigmasterol, lophenol, sitosterol, stigmastanol, ⁵-avenasterol, ⁷-avenasterol and ⁷-stigmastenol) have been identified. The sterol pattern is qualitatively the same, but the relative composition is different in leaves and in seeds. Leaves contain mainly sitosterol, stigmasterol, cholesterol and campesterol, but only minor portions of avenasterols. Seeds contain sitosterol, ⁵- and ⁷-avenasterol, campesterol, but only minor amounts of stigmasterol and cholesterol. In leaf lipids 1-hexacosanol (2.35 wt % of total lipid) has also been identified.     

Lipids of Dark-Treated Oat (Avena sativa) Leaf Chloroplast Thylakoids

The lipid content of thylakoids from dark-treated oat plantswas studied. The levels of chlorophyll, monogalactosyl diacylglycerol²,digalactosyl diacylglycerol, and the phospholipids all declined.The lipids declined more rapidly than the chlorophyll. As thequantity of the galactolipids declined, there was little changein the relative concentration of linolenic acid esterified tothem. In contrast, the relative concentration of linolenic acidesterified to the phospholipids increased as the quantity oflipid declined. The total fatty acid composition and the incorporationof label into thylakoid lipids dropped following the dark treatment.     

Phytochrome Chromophore Biosynthesis : Both 5-Aminolevulinic Acid and Biliverdin Overcome Inhibition by Gabaculine in Etiolated Avena sativa L. Seedlings

Etiolated Avena sativa L. seedlings grown in the presence of gabaculine (5-amino-1,3-cyclohexadienylcarboxylic acid) contained reduced levels of phytochrome as shown by spectrophotometric and immunochemical assays. Photochromic phytochrome levels in gabaculine-grown plants were estimated to be 20% of control plants, while immunoblot analysis showed that the phytochrome protein moiety was present at approximately 50% of control levels. Gabaculine-grown seedlings administered either 5-aminolevulinic acid or biliverdin exhibited a rapid increase of spectrophotometrically detectable phytochrome. Phytochrome concentrations estimated immunochemically did not similarly increase throughout treatment with either compound. Similar experiments with 5-amino[4-¹⁴C] levulinic acid showed radiolabeling of phytochrome with kinetics that paralleled the spectrally detected increase. These results are consistent with (a) the intermediacy of both 5-aminolevulinic acid and biliverdin in the biosynthetic pathway of the phytochrome chromophore and (b) the lack of coordinate regulation of chromophore and apoprotein synthesis in Avena seedlings.     

大粒裸燕麦（莜麦）（Avena nuda L.）起源及分类问题的探讨

燕麦属（Avena L.）植物中有5个栽培种即普通栽培燕麦（A. sativa L.）、埃塞俄比亚燕麦（A. abyssinica Hochst.）、地中海燕麦（A. byzantina Koch）、砂燕麦（A. strigosa Schreb.）和大粒裸燕麦又称莜麦（A. nuda L.）,其中大粒裸燕麦的子粒不带稃皮为裸燕麦,其他物种均带稃皮为皮燕麦。国际上主要种植皮燕麦,而我国主要种植大粒裸燕麦,由此不难看出,大粒裸燕麦在世界燕麦中占有特殊的地位。然而,关于大粒裸燕麦的起源和分类地位问题,迄今学者们的意见仍不尽相同。笔者通过参阅有关文献和研究实践,对这两个问题进行探讨,认为大粒裸燕麦起源于我国山西和内蒙古一带,在植物学分类上应为一个独立的物种即A. nuda L.。     

中国裸燕麦β-葡聚糖含量的鉴定研究

对来源于中国13个省（区）1010份和国外引进的4份裸燕麦品种（系）进行了β-葡聚糖含量的鉴定研究。结果表明,中国裸燕麦β-葡聚糖含量为2．0％～7．5％,其中含量〈3．00％的占6．61％,3．00％～4．99％的占86．4％。5．00％～5．99％的占5．72％,≥6．00％的占1．18％。按品种类型划分,地方品种的含量低于育成品种（系）。按来源地划分,河北、山西、内蒙古的含量较高,云南、贵州、四川的含量较低,而陕西的含量最低。同年不同地点或相同地点不同年份种植的相同品种（系）,含量有一定的变化（0．27％～0．83％）。在鉴定中筛选出一批高β-葡聚糖品种（系）。本研究不仅为燕麦高β-葡聚糖育种提供了理论依据和物质基础,而且为降脂燕麦保健片的生产提供了优良品种。     

The limit dextrinases from ungerminated oats (Avena sativa L.) and ungerminated rice (Oryza sativa L.).

The limit dextrinases from ungerminated oats and rice have been purified, and their substrate specificity compared with a bacterial isoamylase preparation. Both cereal enzymes could hydrolyse (1 yields6)-alpha-D-glucosidic linkages in oligosaccharide alpha-dextrins, pullulan, amylopectin, and the beta-limit dextrins of amylopectin and glycogen. However, under comparable conditions, they were unable to attack glycogens.     

Analysis of the Antimicrobial Activity of Flavonoids and Saponins Isolated from the Shoots of Oats (Avena sativa L.)

Crude extracts from the shoots of oat cv. Quoll were tested against four species of bacteria and eight species of fungi. Bacterial growth was not inhibited. The mycelia growth of all Pyrenophora species tested, except Pyrenophora avenae DAR 33699, was inhibited by the crude extract, whereas the mycelia growth of Fusarium graminearum, Mycosphaerella pinodes and Rhizoctonia solani was not affected. Partially purified fractions with high concentrations of flavone‐C‐glycosides had no inhibitory effect against P. teresf. sp. teres and P. teres f. sp. maculata. The saponin 26‐desglucoavenacoside B accounted for most of the activity against P. teres f. sp. teres with a minor contribution from the other saponins, 26‐desglucoavenacoside A and avenacosides A and B.     

Genetic analysis of oat (Avena sativa L.) by joint scaling test

Comparing the results of genetic analysis of oat varieties with the method of diallel analysis of F1 hybrids and with the joint scaling test the spheres of optimal application of both methods were determined. Quantitative estimation of genetic parameters forming the phenotypic averages in scaling test develops the necessary base for involvement of marker genes for qualitative characters in search of QTLs controlling the traits with continuous variation. The crosses being the most suitable for further investigation with the aim to identify and to allocate the main genes of quantitative traits are indicated.     

Oat (Avena sativa L.) and amaranth (Amaranthus hypochondriacus) meals positively affect plasma lipid profile in rats fed cholesterol-containing diets

Cereals are an important part of diets for hypercholesterolemic patients. However, some of these patients are allergic to these natural products. The purpose of the current study was to compare oatmeal with equal in nutritional values two allergy-free amaranth meals to determine whether this pseudocereal can be a substitute for allergic to cereals individuals. The total phenols of the samples were determined with the Folin-Chocalteu reagent, anthocyanins, and flavonoids spectrophotometrically. The antioxidant activities were estimated with nitric oxide scavenging radical (NO) and by beta-carotene bleaching (beta-carotene). It was found that the contents of different protein fractions, antioxidant compounds, and the antioxidant activities of oatmeal were significantly higher than those of the two amaranth samples. The results of kinetic reactions showed that samples differed in their capacities to quench these radicals, and oats have shown more antioxidant activity than amaranth. High correlation was observed between antioxidant activities and phenols (R(2) = 0.99). In the in vivo part of the investigation, 60 male Wistar rats were divided into five diet groups of 12 animals each; these groups were designated as Control, Chol, Chol/Oat, Chol/AmarI, and Chol/AmarII. The rats of the Control group were fed basal diet (BD) only. To the BD of the four other groups were added the following: 1% of cholesterol (Chol), 10% of oat meal and 1% of cholesterol (Chol/Oat), 10% of amaranth I meal, and 1% of cholesterol (Chol/AmarI) and 10% of amaranth II meal and 1% of cholesterol (Chol/AmarII). After 32 days of different feeding, diets supplemented with oat meal and, to lesser degree, with amaranth I and amaranth II hindered the rise in the plasma lipids: a) TC: 3.14 vs. 4.57 mmol/L, - 31.3%; 3.31 vs. 4.57 mmol/L - 27.6%; and 3.40 vs. 4.57, - 25.6%, respectively b) LDL-C: 1.69 vs. 3.31 mmol/L, - 49.9%; 2.05 vs. 3.31 mmol/L, - 38.1%; and 2.16 vs. 3.31 mmol/L, - 34.8%, respectively; c) TG: 0.73 vs. 0.88 mmol/L, - 17.1%; 0.75 vs. 0.88 mmol/L, - 14.8%; and 0.79 vs. 0.88 mmol/L, -10.2%, respectively. The HDL-PH was increased as follows: 0.79 vs. 0.63 mmol/L, -25.3%; 0.75 vs. 0.63 mmol/L, -23.0%; and 0.71 vs. 0.63 mmol/L, -12.7% for the Chol/Oat, Chol/AmarI and Chol/AmarII, respectively. No significant changes in the concentrations of HDL-C and TPH were found; however the HDL-C in the Chol/Oat group was slightly higher than in other groups. No changes in the Control group were registered. In conclusion, oat and amaranth meals positively affect plasma lipid profile in rats fed cholesterol-containing diets. The degree of this positive influence is directly connected to the contents of the bioactive components and the antioxidant activities of the studied samples. It is suggested that amaranth could be a valuable substitute for hypercholesterolemic patients allergic to cereals.