L-刀豆氨酸的研究进展

L-刀豆氨酸是一种天然的非蛋白质氨基酸,L-精氨酸的类似物.因为其能代替精氨酸进入细胞合成有生理缺陷的蛋白质,从而具有良好的抗肿瘤性,特别是对于胰腺癌具有较好的治疗效果.本文主要对L-刀豆氨酸的抗癌机理和制备方法作了详细的介绍.     

Growth Inhibitory Effects of Nutgrass (Cyperus rotundus) on Rice (Oryza sativa) Seedlings

Growth inhibitory effects of aqueous extracts and leachates of leaves and tubers of Cyperus rotundus L. were investigated by using rice (Oryza sativa L.) seedling as a bioassay material. Both the extracts and leachates of Cyperus were inhibitory to the growth of rice seedlings. Growth inhibition was more pronounced in the presence of aqueous extracts than the leachates. The extract and leachate of leaves had higher total phenolic contents than those of the tubers. Soil amendment with fresh leaves of Cyperus reduced plant height, leaf area, and root and shoot weight of rice seedlings. Total phenolic content was higher in soil amended with fresh Cyperus leaves than the unamended control soil. Nineteen compounds were tentatively identified from the aqueous extracts of leaves and tubers by ethyl acetate extraction followed by gas chromatography–mass spectroscopy (GC-MS). Dicarboxylic, phenolic, and fatty acids were the major compounds. Our results suggest that Cyperus may affect the growth and establishment of rice seedlings after sowing or transplanting, especially when Cyperus plants are mixed in soil during land preparation by ploughing in rain-fed rice culture.     

Impact of Exogenous Silicate Amendments on Nitrogen Metabolism in Wheat Seedlings Subjected to Arsenate Stress

We intended to investigate the response of arsenate on nitrogen metabolism in wheat seedlings and aimed to assess the efficacy of silicon amendments in modulating the metabolic disturbances caused by arsenate stress. The nitrogen metabolism of wheat cultivated in different levels of arsenate with or without silicate in a medium supplemented with modified Hoagland’s solution for 21 days was studied. Experimental design was completely randomized with different arsenate concentrations (0, 25, 50 and 100 μM) with or without 5 mM silicate. Arsenate treatment decreased growth along with decline in nitrate (NO3−) uptake and accumulation. Activities of nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) as well as glutamate synthase (GOGAT) were lowered in the test seedlings. Decline in nitrite (NO2−) and amino acid contents were also evident along with an enhancement in the accumulation of toxic ammonia. Silicate supplementation under arsenate stress however, improved growth, repaired the arsenate-induced effects leading to an enhancement in nitrate (NO3−) uptake and consequently improved nitrite (NO2−) and amino acid contents as well. The total and soluble nitrogen contents were enhanced along with enhancements in activities of enzymes associated with nitrate metabolism while ammonia accumulation was lowered. Results therefore, imply the involvement of exogenous silicon amendments in relieving the metabolic alterations in nitrogen metabolism caused by arsenate stress that enabled wheat seedlings to adapt under arsenate excess and eventually promoted plant growth.     

Why Phenolic Acids Are Unlikely Primary Allelochemicals in Rice

Allelopathy in rice (Oryza sativa, L.) effective against weeds has been found in about 3.5% of tested rice germplasm in both laboratory and field experimentation. However, the allelochemicals responsible for growth inhibition of rice-associated weeds have not yet been identified. In the literature, phenolic acids are often mentioned as putative allelochemicals. If phenolic acids commonly reach growth inhibitory concentrations in rice ecosystems, it must be expected that the degree of tolerance to phenolic acids will vary among traditional rice cultivars or plant species adapted to rice environments having inherently different phenolic acid concentrations. Phenolic acids concentrations are normally greater in submerged than in aerobic soils. A dose–response study, however, showed that seedlings of rice cultivars adapted to submerged anaerobic soils did not have higher level of tolerance against p-hydroxybenzoic acid than did seedlings of varieties adapted to aerobic upland soils. Moreover, traditional rice cultivars had no greater tolerance than did improved cultivars that were recently bred for traits other than tolerance of phenolic acids. Similarly, there were no differences in tolerance of p-hydroxybenzoic acid between two Echinochloa weed species adapted to either anaerobic or aerobic growth conditions. Thus, neither the rice cultivars nor weed species had evolved different tolerance levels against the phenolic acid. However, all rice cultivars had significantly greater tolerance of p-hydroxybenzoic acid than did either weed species. In a second experiment, the rates at which rice plants released phenolic acids into solution cultures were measured for at least one month, the time period of greatest allelopathic activity following planting under field conditions. The maximum release rate of phenolic acids during the first month of growth was approximately 10 g/plant/day. At a conventional plant density, the release rate of phenolic acids would be approximately 1 mg/m²day. This order of release rate cannot provide concentrations remotely close to phytotoxic levels determined for these rice cultivars and weed species. The results presented in this paper do not preclude the possibility that phenolic acids might be one component in a mixture of chemicals that, when present simultaneously, are allelopathic.     

Inhibition of protein synthesis in lettuce (Latuca sativa L.) by allelopathic compounds

The effects of ferulic, cinnamic, and ellagic acids on the development of roots and protein synthesis in lettuce seedlings (Latuca sativa L., variety of Black Seeded Simpson) are reported here. Both ferulic and cinnamic acids were found to inhibit protein synthesis of the seedlings either when added from the beginning of the germination period, or when added for a short period of time to seedlings which had already germinated under control conditions. Ellagic acid, at the same pH and osmotic concentrations as the effective inhibitors, was completely ineffective in inhibiting either growth of roots or protein synthesis. It is shown that utilization of [¹⁴C] amino acid incorporation into seedlings appears to be a sensitive, reliable, and appropriate indicator of allelopathic inhibition of plant growth. Utilizing this method, it should be possible to determine if the effect on protein synthesis by putative allelopathic compounds is a general phenomenon and may, in turn, help to elucidate the role of these compounds.     

Autointoxication mechanism ofOryza sativa I. Phytotoxic effects of decomposing rice residues in soil

The aqueous extracts of decomposing rice residues in soil exhibited inhibition on the radicle growth of lettuce and rice seeds and the growth of rice seedlings. The phytotoxicity was found in extracts obtained from the early stage of decomposition (first month), and gradually declined thereafter. The inhibition was also found in extracts obtained from rice fields, and was persistent for 4 months. The root initiation of hypocotyl cuttings of mungbeans was suppressed by extracts of decaying rice residues and extracts obtained from paddy soil. Five phytotoxins,p-hydroxybenzoic,p-coumaric, vanillic, ferulic, ando-hydroxyphenylacetic acids, and several unknowns were found in the decomposing rice residues under waterlogged conditions. At 25 ppm,o-hydroxyphenylacetic acid revealed significant inhibition on the radicle growth of rice and lettuce seeds and suppressed root initiation of mungbean seedlings. It was concluded that the growth of rice seedlings was retarded by decaying rice residues in soil; thus, this appeared to be an autointoxication phenomenon.Paper No. 176 of the Scientific Journal Series, Institute of Botany, Academia Sinica. This study was financially supported by the National Science Council, the Republic of China.     

3-Methylarginine from Pseudomonas syringae pv. syringae 22d/93 suppresses the bacterial blight caused by its close relative Pseudomonas syringae pv. glycinea

The epiphyte Pseudomonas syringae pv. syringae 22d/93 (Pss22d) produces a toxin that strongly inhibits the growth of its relative, the plant pathogen P. syringae pv. glycinea. The inhibition can be overcome by supplementing the growth medium with the essential amino acid, L-arginine; this suggests that the toxin acts as an inhibitor of the arginine biosynthesis. The highly polar toxin was purified by bioassay-guided fractionation using ion-exchange chromatography and subsequent RP-HPLC fractionation. The structure of the natural product was identified by HR-ESI-MS, HR-ESI-MS/MS, and NMR spectroscopy experiments as 3-methylarginine. This amino acid has previously only been known in nature as a constituent of the peptide lavendomycin from Streptomyces lavendulae. Results of experiments in which labeled methionine was fed to Pss22d indicated that the key step in the biosynthesis of 3-methylarginine is the introduction of the methyl group by a S-adenosylmethionine (SAM)-dependent methyltransferase. Transposon mutagenesis of Pss22d allowed the responsible SAM-dependent methyltransferase of the 3-methylarginine biosynthesis to be identified.     

Inhibition of fatty acid synthesis in isolated adipocytes by 5-(tetradecyloxy)-2-furoic acid

The compound 5-(tetradecyloxy)-2-furoic acid (TOFA), a hypolipidemic agent, inhibits fatty acid synthesis, lactate and pyruvate accumulation and CO₂ release in isolated at adipocytes. TOFA stimulates the accumulation of citrate. ATP levels are not lowered by TOFA. In comparison with the natural fatty acid, oleate, TOFA exhibited a much greater inhibitory effect on lipogenesis. TOFyl-CoA formation within intact adipocytes was demonstrated. Although not inhibited by TOFA, acetyl-CoA carboxylase is inhibited by TOFyl-CoA. It is proposed that many of the metabolic effects of TOFA in isolated adipocytes can be explained by TOFyl-CoA inhibition of acetyl-CoA carboxylase. TOFA inhibits glycolysis as a secondary event with the primary event of inhibition of fatty acid synthesis causing an accumulation of citrate which is an inhibitor of phosphofructokinase.     

DA-6缓解胺苯磺隆对后茬水稻伤害的作用

室内采用土培法分别测定了不同浓度胺苯磺隆和不同浓度己酸二乙氨基乙醇酯(简称DA-6)对水稻生长的影响以及不同浓度胺苯磺隆处理下DA-6对水稻根生长的影响。结果表明,胺苯磺隆处理浓度自0.1μg/kg起,明显抑制水稻幼苗的生长,且对主根长和根鲜重的抑制作用较株高和株鲜重更为严重;当DA-6浓度在0.5~20mg/L范围内,水稻根长和根鲜重高于对照,其中以5mg/L最好;用5mg/L的DA-6浸种可不同程度地缓解0.1~20μg/kg的胺苯磺隆对水稻的伤害。     

腐植酸类水稻育秧剂适宜酸度研究

2006年3月至5月在辽宁普天同乐肥业有限公司试验基地安排了腐植酸水稻育秧剂适宜酸度试验,并与抚顺育秧剂进行对比。结果表明,腐植酸水稻育秧剂能增加株高、根长、叶片长、叶片宽和基茎粗,分别比对照增加4.17%～12.28%,1.03%～6.63%,3.05%～9.91%,1.30%～13.64%,3.09%～8.25%;根鲜重、茎叶鲜重、根干重、茎叶干重、总鲜重和总干重分别比对照增加12.36%～47.19%,11.76%～30.15%,25.00%～37.50%,8.82%～29.41%,12.00%～36.00%,14.00%～30.00%;根系的总吸收面积和活跃吸收面积分别比对照增加12.15%～74.24%和12.54%～74.49%。试验结果表明,利用中性和弱酸性草甸土育苗,腐植酸育秧剂适宜pH值为4或5。     

Evaluation of Putative Allelochemicals in Rice Root Exudates for Their Role in the Suppression of Arrowhead Root Growth

In previous studies, 15 putative allelopathic compounds detected in rice root exudates were quantified by GC/MS/MS. In this study, multiple regression analysis on these compounds determined that five selected phenolics, namely caffeic, p-hydroxybenzoic, vanillic, syringic, and p-coumaric acids, from rice exudates were best correlated with the observed allelopathic effect on arrowhead (Sagittaria montevidensis) root growth. Despite this positive association, determination of the phenolic acid dose-response curve established that the amount quantified in the exudates was much lower than the required threshold concentration for arrowhead inhibition. A similar dose-response curve resulted from a combination of all 15 quantified compounds. Significant differences between the amounts of trans-ferulic acid, abietic acid, and an indole also existed between allelopathic and non-allelopathic rice cultivars. The potential roles of these three compounds in rice allelopathy were examined by chemoassay. Overall, neither the addition of trans-ferulic acid nor 5-hydroxyindole-3-acetic acid to the phenolic mix significantly contributed to phytotoxicity, although at higher concentrations, trans-ferulic acid appeared to act antagonistically to the phytotoxic effects of the phenolic mix. The addition of abietic acid also decreased the inhibitory effect of the phenolic mix. These studies indicate that the compounds quantified are not directly responsible for the observed allelopathic response. It is possible that the amount of phenolic acids may be indirectly related to the chemicals finally responsible for the observed allelopathic effect.     

Metabolite Profiling of Diverse Rice Germplasm and Identification of Conserved Metabolic Markers of Rice Roots in Response to Long-Term Mild Salinity Stress

The sensitivity of rice to salt stress greatly depends on growth stages, organ types and cultivars. Especially, the roots of young rice seedlings are highly salt-sensitive organs that limit plant growth, even under mild soil salinity conditions. In an attempt to identify metabolic markers of rice roots responding to salt stress, metabolite profiling was performed by ¹H-NMR spectroscopy in 38 rice genotypes that varied in biomass accumulation under long-term mild salinity condition. Multivariate statistical analysis showed separation of the control and salt-treated rice roots and rice genotypes with differential growth potential. By quantitative analyses of ¹H-NMR data, five conserved salt-responsive metabolic markers of rice roots were identified. Sucrose, allantoin and glutamate accumulated by salt stress, whereas the levels of glutamine and alanine decreased. A positive correlation of metabolite changes with growth potential and salt tolerance of rice genotypes was observed for allantoin and glutamine. Adjustment of nitrogen metabolism in rice roots is likely to be closely related to maintain the growth potential and increase the stress tolerance of rice.     

Influence of Pretreatment Stresses on Inhibitory Effects of Ferulic Acid, an Allelopathic Phenolic Acid

Experiments were conducted to determine the potential for acclimation (i.e., increased tolerance) to allelopathic phenolic acids resulting from pretreatment of seedlings with allelochemical (ferulic acid), drought, or nutrient stress. Cucumber seedlings were exposed to pretreatment stresses in a nutrient culture system for nine days, starting with day 3. Seedlings were subsequently treated for 5 hr with 0, 0.25, 0.5, or 0.75 mM ferulic acid. Acclimation (tolerance) was quantified by percentage inhibition of net phosphorus uptake. Seedlings grown with ferulic acid or drought pretreatment stresses were more tolerant to subsequent ferulic acid treatments (i.e., inhibition of net phosphorus uptake by ferulic acid was reduced). Nutrient pretreatment stress eliminated the inhibitory activity of ferulic acid on net phosphorus uptake. The results suggest that a general acclimation response to a variety of pretreatment stresses can confer an increased tolerance of plants to allelopathic phenolic acids such as ferulic acid.     

Allelopathic Potential of Aquatic Plants Associated with Wild Rice (Zizania palustris): I. Bioassay with Plant and Lake Sediment Samples

The allelopathic potential of eight aquatic plants associated with wild rice was investigated using lettuce and wild rice seedling bioassays. Rhizome aqueous extracts of Scirpus acutus, Potamogeton natans, Nymphaea odorata, Nuphar variegatum; shoot extract of Eleocharis smallii; whole plant extract of Myriophyllum verticillatum; and leaf extract of P. natans significantly reduced the root length of lettuce and wild rice seedlings. The lettuce seedling bioassay was more sensitive than the wild rice bioassay. Shoot growth was less affected than the root growth. Water extract of sediments associated with the aquatic plants had little growth inhibitory effect on wild rice. Our study did not yield any conclusive evidence that the wild rice-associated aquatic plants have allelopathic effects on wild rice. We emphasize the use of target species as a bioassay material in allelopathic studies. Further investigation on allelopathic effects of lake sediments associated with the neighboring plants of wild rice is necessary to evaluate their ecological significance.     

三十烷醇磷酸酯钾的生物活性检测

用０．００１、０．０１、０．１、１．０ｍｇ／Ｌ的三十烷磷酸酯钾（ＴＰＫ）溶液培养小麦、水稻幼苗。其促进幼苗根、茎叶器官生长的能力以０．０１ｍｇ／Ｌ为最佳,使小麦幼苗的苗高、苗鲜重、苗干重、根长、根鲜重、根干重、全株鲜重和全株干重分别比甭水对照提高１７．１％、１７．０％、１８．４％、１６．４％￣１１．０％、１２．０％、１５．０％和１７．０％,使水稻幼的上述指标分别提高１０．３％、１１．０％、４０．３     

CAN SIMULTANEOUS INHIBITION OF SEEDLING GROWTH AND STIMULATION OF RHIZOSPHERE BACTERIAL POPULATIONS PROVIDE EVIDENCE FOR PHYTOTOXIN TRANSFER FROM PLANT RESIDUES IN THE BULK SOIL TO THE RHIZOSPHERE OF SENSITIVE SPECIES?

In order to demonstrate that allelopathic interactions are occurring, one must, among other things, demonstrate that putative phytotoxins move from plant residues on or in the soil, the source, through the bulk soil to the root surface, a sink, by way of the rhizosphere. We hypothesized that the incorporation of phytotoxic plant residues into the soil would result in a simultaneous inhibition of seedling growth and a stimulation of the rhizosphere bacterial community that could utilize the putative phytotoxins as a sole carbon source. If true and consistently expressed, such a relationship would provide a means of establishing the transfer of phytotoxins from residue in the soil to the rhizosphere of a sensitive species under field conditions. Presently, direct evidence for such transfer is lacking. To test this hypothesis, cucumber seedlings were grown in soil containing various concentrations of wheat or sunflower tissue. Both tissue types contain phenolic acids, which have been implicated as allelopathic phytotoxins. The level of phytotoxicity of the plant tissues was determined by the inhibition of pigweed seedling emergence and cucumber seedling leaf area expansion. The stimulation of cucumber seedling rhizosphere bacterial communities was determined by the plate dilution frequency technique using a medium containing phenolic acids as the sole carbon source. When sunflower tissue was incorporated into autoclaved (to reduce the initial microbial populations) soil, a simultaneous inhibition of cucumber seedling growth and stimulation of the community of phenolic acid utilizing rhizosphere bacteria occurred. Thus, it was possible to observe simultaneous inhibition of cucumber seedlings and stimulation of phenolic acid utilizing rhizosphere bacteria, and therefore provide indirect evidence of phenolic acid transfer from plant residues in the soil to the root surface. However, the simultaneous responses were not sufficiently consistent to be used as a field screening tool but were dependent upon the levels of phenolic acids and the bulk soil and rhizosphere microbial populations present in the soil. It is possible that this screening procedure may be useful for phytotoxins that are more unique than phenolic acids.     

Environmental Effects on the Accumulation of Hydroxamic Acids in Wheat Seedlings: The Importance of Plant Growth Rate

The effects of temperature and photoperiod on accumulation of hydroxamic acids (Hx) in wheat (Triticum aestivum L.) seedlings were evaluated under laboratory conditions. Hx concentrations were significantly higher at higher temperatures. No such clear trend was found for the photoperiod effect. The significant effect of temperature and photoperiod on growth rate of seedlings and the significant positive correlation between growth rate prior to analysis and levels of Hx, suggested that environmental effects on Hx accumulation were at least partially mediated through their effect on plant growth rate. After uncoupling the effect of environmental conditions from the effect of plant growth rate by statistical means the effect of temperature on Hx was no longer significant. Therefore, temperature effect was fully mediated by plant growth rate. Implications of the patterns found are discussed in issues of plant-defense general theories.     

Nitrogen behavior in tropical wetland rice soils

Laboratory and greenhouse pot experiments show that tropical wetland rice soils are very diverse in the inherent fertility. The mineralization of native soil nitrogen differed among the soils studied. Air-drying and oven-drying of soils resulted in a large increase in nitrogen mineralized. The main source of mineralized N was the amino acid and amino sugar fractions.N uptake by rice was well correlated with N mineralized in incubation of air-dried soil which should reflect accurately the nitrogen-supplying capacities of tropical wetland rice soils during the growing season. However, plant uptake of available soil nitrogen was also correlated with total nitrogen content of soils, and it would appear that total soil nitrogen which is simple to determine is a satisfactory index of the N supplying capacities of tropical wetland rice soils. Exclusion of problem soils like acid sulfate soils improved the correlation.