Nucleic Acid Metabolism in the Developing Primary Leaf and Senescing Coleoptile of Germinating Oats

Nucleic acid metabolism in the coleoptile and primary leaf tissues of the germinating oat (Avena sativa L.) seedling was studied. The concentrations of the different species of nucleic acid present at various stages of development were determined and the amounts of each compared. All species of nucleic acid in the coleaptile increased as the tissue elongated; but, with the onset of senescence all species decreased, especially rRNA. Exposing dark grown coleoptiles to light did not modify their capacity to synthesize nucleic acids. In the rapidly developing leaf, all species of nucleic. acid increased throughout early germination. A general enhancement in the synthesis of all species of nucleic acids resulted when dark-grown-leaves were exposed to light. Furthermore, the tRNA/DNA ratio remained constant in both tissues during development, whereas the rRNA/DNA ratio changed.     

Ribonucleic Acid Metabolism in Germinating Soybeans

A stereoselective synthesis of methyl trans, trans-farnesoate (I) from isoprenyl bromide and geraniol is described. dl-C₁₇-Cecropia juvenile hormone (IV) was synthesized from it in a stereoselective manner.     

Respiratory Mechanisms and the Changes of Glutathione and Ascorbic Acid in Germinating Peas

The respiration of pea seeds during the early stages of germinationwas studied by manometric methods. From analyses of the germinatingseeds estimates were obtained of the oxidized and reduced formsof glutathione and ascorbic acid. Thus it was possible to explorethe relationship between these oxidation-reduction systems andthe resumption of respiratory activities in the dormant seed. Several lines of evidence indicate that partial anaerobiosisis an important feature of metabolism during the first phasesof germination in air. The intact testa, acting as a barrierto diffusion, limits the uptake of oxygen by the seed. Splittingof the testa by the development of the embryo leads to rapidchanges in the mechanism and rate of respiration. An increase in the relative proportions of the reduced formsof both glutathione and ascorbic acid is associated with theestablishment of anaerobic conditions in the seed. This andother available evidence indicate that the glutathione-ascorbicacid carrier system plays only a minor part in aerobic oxidationsduring the early stages of germination. The possibility thatglutathione has an important influence on the activation ofenzymes in the first phase of germination is briefly considered.     

Effects of Some Inhibitors of Nucleic Acid and Protein Synthesis on the Development of Amine Oxidase in Germinating Pea Cotyledons

The germination of pea seed was accompanied by a rapid increase of amine oxidase (E.C. 1.4.3.6.) in the cotyledon and over half the increase was ascribable to the presence of axial tissue. The presence of actinomycin D, 6-methylpurine and cycloheximide in the early period of soaking inhibited markedly the increase in amine oxidase activity. However, actinomycin D and cycloheximide had little effect on the enzyme development when added after one day and 2 days of germination respectively. The amine oxidase development was also inhibited by dl -p-fluorophenylalanine, 5-methyltryptophan, chloramphenicol and phenylthiourea.     

Development of Pyrimidine-metabolizing Enzymes in Cotyledons of Germinating Peas

Mechanisms controlling conversion of orotic acid-6-¹⁴C to uridine-5′-phosphate in cotyledons of germinating Alaska peas (Pisum sativum L.) were investigated. The content of 5-phosphoribosyl-1-pyrophosphate was very low in dry seeds, increased to a maximum after about 12 hours of imbibition, and then rapidly declined. Orotidine-5′-phosphate pyrophosphorylase and orotidine-5′-phosphate decarboxylase activities more than doubled during the first 24 hours of germination and then also decreased. These results do not account for the continuous increases of orotate anabolism in such cotyledons as we observed previously. The initial increases in activities of these two enzymes were unaffected by cycloheximide, while the subsequent decreases were less rapid in the presence of this inhibitor. Activities of cotyledonary cytidine deaminase and uridine hydrolase also increased during imbibition, but the activity of only the latter showed a decrease after imbibition was completed. Cycloheximide inhibited the initial rapid increase in uridine hydrolase activity but had little effect on its subsequent decline. Cycloheximide had only slight inhibitory effects on the development of cytidine deaminase activity during the first 62 hours. The evidence suggests that uridine hydrolase might be synthesized de novo during the first few days of germination, but that the other three enzymes might not be.     

Nutrient Uptake and Organic Acid Anion Metabolism in Lupins and Peas Supplied with Nitrate

Unlike many plants reported in the literature, lupins do notexcrete OH^- in amounts equivalent to the net excess of inorganicanion uptake over inorganic cation uptake. To investigate themechanisms involved in the maintenance of charge balance, nutrientuptake and organic anion accumulation of lupins and peas suppliedwith a range of NO^-₃ concentrations, were compared. Lupins absorbed less NO^-₃ than peas on a dry weight basis, whichlargely accounted for the smaller excess of anion uptake overcation uptake in lupins than in peas at the same NO^-₃ supply.When anion uptake exceeded cation uptake, peas excreted an equivalentcharge of OH^-, whereas lupins excreted much smaller amountsof OH^- than the excess of anion over cation uptake. It was calculatedthat lupins excreted significant amounts of organic anions whenanion uptake exceeded cation uptake, whereas organic anion excretionfrom peas was negligible, regardless of their NO^-₃ supply andcation-anion balance. In this study, organic anion excretion was measured from lupinroots grown in near-sterile conditions while supplied with NO^-₃at 0, 500 and 2000 µM. Although complete sterility wasnot achieved, there was close agreement between the organicanion excreted and the excess anion over cation uptake.Copyright1994, 1999 Academic Press Lupinus angustifolius L., Pisum sativum L., organic acid, nutrient uptake     

Nucleic Acid Metabolism During Cytokinin Induced Cellular Differentiation

Edstrom's microphoresis technique has been employed to determine the quantitative alterations in nucleic acid content and base composition of individual cells associated with the initiation of bud primordia in Funaria hygrometrica. The filamentous protonema of this moss initiates bud cells which through repeated divisions form the leafy gametophores. The cytokinin, 6-furfurylaminopurine (kinetin), was used to induce the differentiation of bud cells from protonematal cells. The total RNA content of kinetin-induced bud cells (22.0 μμg/cell) was nearly 15 times that of protonematal cells (1.6 μμg/cell). The same dramatic increase in total RNA was apparent in bud cells which developed spontaneously in older cultures. As would be predicted, the adenine (A) to guanine (G) ratio for DNA from bud and protonematal cells was identical (0.7). The A:G ratio for RNA from bud cells (1.0) was much lower than that from protonematal cells (1.7). Thus, kinetin-induced differentiation in this system involves a dramatic increase in total RNA, the base composition of which approaches that of DNA. The base composition (A:G ratio) of DNA remains constant.     

Nucleic Acid Metabolism in Chlamydomonas moewusii Undergoing Daily Cell Doubling

Nucleic acid metabolism was studied in synchronized cultures(12 h light, 12 h dark) of Chlamydomonas moewusii Gerloff inwhich cell number approximately doubled each 24 h. Analysisfor DNA showed a small but significant rise between 5 to 7 hand a major increase from 11 to 16 h after first exposure tolight. Cellular RNA levels increased from 0·5 to 1·1pg within 1 h after exposure to light, dropped after 2 h toa plateau value of about 0·9 pg, declined from the 10thto the 17th hour, and subsequently increased a second time duringthe dark period. Investigations using gel electrophoresis showedthat RNAs of chloroplastic ribosomes were only a minor componentin extracts obtained in the first 8 h of light. It is suggestedthat the time of initiation of synthesis and degradation aswell as the nature and amounts of nucleic acids produced inChlamydomonas are regulated by conditions of growth.     

Nucleic Acid Metabolism of Vicia faba during Germination and Growth

During the growth of Vicia faba seedlings in the absence of an external nitrogen supply, the cotyledons decreased rapidly in dry weight and nucleic acid content. In the developing shoot the dry weight increased rapidly for four weeks and then very slowly over the next two weeks growth; the nucleic acid content of the shoot increased to a maximum after 4 weeks growth and decreased in amount during the next 2 weeks. On the other hand the roots increased in both dry weight and nucleic acid content throughout the growth period, although they only accounted for a small proportion of the total dry weight and nucleic acid content of the plant. These changes during germination and growth are discussed in relation to those occurring during these developmental stages in other plants.     

Comparative Analysis of Nucleic Acid and Protein Primary Structures

The review considers the original works on the primary structure of biopolymers carried out from 1983 to 2003. Most works were supported by the Russian program Human Genome and earlier similar Russian programs. Little-known publications of 1983–1993 and recent unpublished results are described in detail. In the field of genome comparisons, these concern the OWEN hierarchic algorithm aligning syntenic regions of two genome sequences. The resulting global alignment is obtained as an ordered chain of local similarities. Alignment of megabase sequences takes several minutes. The concept of local similarity conflicts is generalized to multiple comparisons. New algorithms aligning protein sequences are described and compared with the Smith–Waterman algorithm, which is now most accurate. The ANCHOR hierarchic algorithm generates alignments of much the same accuracy and is twice as rapid as the Smith–Waterman one. The STRSWer algorithm takes into account the secondary structures of proteins under study. With the secondary structures predicted using the PSI-PRED software for pairs of proteins having 10–30% similarity, the average accuracy of alignments generated by STRSWer is 15% higher than that achieved with the Smith–Waterman algorithm.     

Protein and Nucleic Acid Metabolism in Fruits: I. Studies of Amino Acid Incorporation During the Climacteric Rise in Respiration of the Avocado

Incorporation of (14)C L-valine and (14)C L-leucine into protein of tissue slices of the avocado fruit was relatively high during the early stages of the climacteric rise, declined sharply thereafter, and was virtually absent at the peak. The incorporation of amino acids in the preclimacteric stage was markedly lower than during the early stage of the respiratory rise. By following incorporation in relation to uptake at several concentrations it was established that the results were not a reflection of endogenous dilution.Puromycin was effective as an inhibitor of incorporation but not of oxygen uptake. When respiration was at its maximum there was no protein synthesis. It was concluded, therefore, that the respiratory upsurge characteristic of the climacteric was not related directly to protein synthesis.     

Effects of Phosfon-S on Nucleic Acid Metabolism in Pisum sativum Alaska

Phosfon-S, a substance which inhibits stem elongation, alters nucleic acid metabolism in Pisum sativum Alaska. Methylated albumin kieselguhr (MAK) columns were used to fractionate ³²P-labeled nucleic acids. Phosfon-S treatment of the plants resulted in a decrease in soluble RNA and an increase in ribosomal RNA. Specific activities of the various nucleic acid fractions were lower as a result of treatment. The nucleic acids from treated tissues were more resistant to RNase degradation, and endogenous RNase activity was lower in treated tissues. When RNase treated nucleic acids were fractionated on MAK columns, the DNA-RNA fractions from treated plants had a higher specific activity than that of the control, which was not true before nuclease treatment. Spectrophotometric examination of this fraction revealed a difference in absorption spectra, possibly indicating a Phosfon-S nucleic acid complex. It is suggested that these alterations in nucleic acid metabolism could in turn alter a wide variety of metabolic processes, resulting in retarded growth.     

Nucleic Acid Metabolism during Greening and Unrolling of Barley Leaf Segments

Barley (Hordeum vulgare) leaf segments unroll and green when illuminated. Illuminated segments also have an increased capacity for RNA synthesis. Part of this increased RNA synthesis may be attributed to an increased RNA polymerase activity. In addition, following illumination there is an increased formation of polysomes.     

莲胚发育与核酸,蛋白质含量的变化

莲胚发育达到最大鲜重(开花后21d)前,胚轴和子叶的DNA,RNA都持续增长。开花13d后,蛋白、淀粉等贮藏物质显著积累,核酸增长速度加快。成熟胚轴的DNA和RNA含量很高,而子叶中积累大量的淀粉、可溶性糖和蛋白质。发育前期胚乳的生长速度较快,开花后16d左右鲜重和物质积累达到高峰。胚生长后期胚乳逐渐败育,贮藏物质和结构物质都减少,膨大的子叶逐步取代了胚乳的地位。 莲胚生物大分子物质含量的模式属于双子叶植物类型。讨论了莲胚细胞多倍化的问题。     

悬浮芯片在核酸和蛋白质检测中的应用

悬浮芯片是近年来兴起的一种新型检测技术,不同于固相基因芯片,它整合了高分子化学、分子生物学、免疫学、激光检测、微流体、高速数字信号处理、计算机分析等方面的先进技术,能够对少量样本进行高通量的定性、定量检测。主要综述了悬浮芯片技术的基本原理,并概要介绍了其在核酸和蛋白质检测中的应用。悬浮芯片技术在核酸和蛋白质检测中有着显著的优点,如高通量、操作简便、重复性好、灵敏度高、线性范围宽等,不但可以广泛应用于科学研究领域,而且还将逐渐普及于临床诊断实验室,具有广阔的应用前景。     

Fat Metabolism in Germinating Citrullus vulgaris

A column chromatographic technique, enabling identificationand quantitative estimation of fatty acids, has been employedto study fat metabolism in Citrullus during germination in thelight. This plant is characterized by an unusually rapid disappearanceof storage fat as the cotyledons expand and turn green. In spiteof the high catabolic activity there is no evidence for accumulationof free fatty acids or short-chain fatty acids at this stage.Information on this point derived from acid value or saponificationvalue of the oil is shown to be untrustworthy. Citrullus seed fat contains the following percentages of acids:linoleic 70·6, oleic 7·2, palmitic 10·1,stearic 11·2, and arachidic 0·6, and careful analysishas also revealed small amounts of octadecatrienoic acids, bothconjugated and non-conjugated. All the major acids are brokendown at rates proportionate to the quantities originally present,with the exception of oleic acid which is metabolized somewhatmore rapidly. ‘Linolenic’ acid is synthesized in the expandinggreen cotyledons and the fatty acid composition of the latter,in the late germination stages, resembles that of a green leafand is very different from that of the seed. The results suggest a rapid removal of storage fat from thecotyledons and concomitant formation in small quantity of atypial leaf fat as the new photo-synthetic function develops.