Ethambutol-Mediated Alterations in Ribonucleic Acid Components of Mycobacterium smegmatis

Polyacrylamide gel electrophoresis of ribonucleic acid (RNA) components from Mycobacterium smegmatis exposed to ethambutol shows that the early effect of the drug produces a selective alteration of some RNA species, suggestive of a noncoordinate control of RNA metabolism.     

Selective Inhibition of Reovirus Ribonucleic Acid Synthesis by Cycloheximide

Cycloheximide, at a concentration of 10 mug/ml, rapidly blocked protein synthesis in L cells infected with reovirus. When the drug was added before 5 hr postinfection, synthesis of both single- and double-stranded varieties of virus-specific ribonucleic acid (RNA), which normally commences between 6 and 7 hr after infection, was blocked. When the cycloheximide was added at 9 hr after infection, uptake of uridine-H(3) into RNA, for the succeeding 6 hr at least, was similar to that of an infected culture without the drug. This latter uptake of uridine-H(3) in the presence of cycloheximide was largely into single-stranded RNA, since double-stranded RNA synthesis was rapidly and markedly inhibited by the cycloheximide. Single-stranded RNA formed in the presence of cycloheximide was found not to be a precursor of viral progeny, double-stranded RNA. Synthesis of double-stranded RNA in the infected cell probably requires prior synthesis of a new protein, which has a rapid rate of turnover. The possibility that formation of single-stranded RNA is preceded by synthesis of a second new protein is discussed.     

脱落酸对玉米胚芽和大豆子叶线粒体呼吸的影响

在提取玉米和大豆线粒体后,以ABA处理线粒体,发现在不同底物存在下,ABA均可增加线粒体的耗氧速率,呼吸速率随ABA浓度变化的结合常数（Kd）值为1．43μmol／L。ABA对4态呼吸的促进作用更为显著,因而导致呼吸控制下降,P／O比降低。蛋白质合成抑制剂环己酰亚胺不影响ABA的效应。以ABA预处理大豆子叶,虽然也促进了呼吸作用,但不改变呼吸控制和P／O.     

The Metabolism of Abscisic Acid

The light-catalysed isomerization of (+)-abscisic acid (ABA)to its trans isomer during isolation from leaves was monitoredby the addition of (±)-[2-¹⁴C]ABA to the extraction medium.(+)Trans-abscisic acid (t-ABA) was found to occur naturallyin rose (Rosa arvensis) leaves at 20µg/kg fresh weight;(+)-ABA was present at 594µg/kg. (±)-[2-¹⁴D]Trans-abscisicacid was not isomerized enzymically to ABA in tomato shoots. (±)-Abscisic acid was converted by tomato shoots to awater-soluble neutral product, ‘Metabolite B’, whichwas identified as abscisyl-ß-D-glucopyranoside. When(±)-[2-¹⁴C]trans-abscisic acid in an equimolar mixturewith (±)-[2-¹⁴C}ABA was fed to tomato shoots it was convertedto its glucose ester 10 times faster than was ABA. Trans-abscisyl-ß-D-glucopyrano8ide only was formedfrom (±)-[2-¹⁴C]t-ABA in experiments lasting up to 30h. Glucosyl abscisate was formed slowly from ABA and the freeacid fraction contained an excess of the unnatural (–).ABAas did the ABA released from abscisyl-ß-D-glucopyranosideby alkaline hydrolysis. The (+).ABA appeared to be the solesource of the acidic ‘Metabolite C" previously noted. The concentrations of endogenous (+)-, (+)-[2-¹⁴C]-, and (–)-[2-¹⁴C]ABAremaining as free acid, and also in the hydrolysate of abscisyl-ß-D-glucopyranoside,were measured by the ORD, UV absorption, and scintillation spectrometryof highly purified extracts of ABA from tomato shoots whichhad been supplied with racemic [2-^l4C]ABA.     

The Effect of Auxin and Abscisic Acid on the Catabolism of RNA

Abscisic acid (ABA) reduced growth in a root test (lentil),but the inhibition observed was less noticeable than that producedby using indol-3yl-acetic acid (IAA) alone. When both ABA andIAA were employed together, ABA acted as a growth-antagonistof IAA. ABA produced a strong inhibition of the total RNA accumulationand accelerated the RNase activity, while IAA strongly stimulatedthe RNA accumulation and greatly inhibited RNase activity. WhenABA and IAA were tested together, ABA also acted as an antagonistof TAA.     

Ribonucleic Acid Polymerase Catalyzing Synthesis of Double-stranded Arbovirus Ribonucleic Acid

The large-particle fraction from the cytoplasm of chick embryo fibroblasts infected with Semliki Forest virus was found to catalyze the incorporation of the 5'-triphosphates of guanosine, adenine, cytidine, and uridine into an acid-insoluble alkali-labile product. The conditions affecting the preparation and assay of this enzyme were investigated. The ribonucleic acid (RNA) polymerase was not present in uninfected cells, and it appeared in infected cells at the time of rapid viral RNA synthesis. The polymerase was found to catalyze the synthesis of a species of RNA which was resistant to ribonuclease and which exhibited the sedimentation properties, buoyant density, and thermal transition temperature of the double-stranded RNA found in vivo in chick cells infected with Semliki forest virus. Attempts to demonstrate that the reaction product of this enzyme also included single-stranded viral RNA were not successful. Although other interpretations are possible, these results give some support to the suggestion that more than one enzyme may be involved in the replication of viral RNA.     

The Influence of Syringomycin on Ribonucleic Acid Synthesis

Syringomycin, a wide-spectrum antibiotic produced by strains of Pseudomonas syringae which cause bacterial canker of peach, was able to bind to salmon sperm and calf thymus deoxyribonucleic acid but not to calf thymus histone; it also inhibited ribonucleic acid polymerase activity. These abilities to bind to deoxyribonucleic acid and to inhibit ribonucleic acid polymerase were inactivated when the phytotoxic and antibiotic properties of syringomycin were inactivated.     

Effect of Myxovirus Infection on Synthesis of Cellular Ribonucleic Acid

Ribonucleic acid (RNA) synthesis of chick embryo fibroblasts was inhibited by two members of the myxovirus group, Newcastle disease virus (NDV) and fowl plague virus. It was also found that cellular deoxyribonucleic acid-dependent RNA polymerase was inhibited by a cytoplasmic factor induced by NDV infection.     

Studies on Abscisic Acid

Methyl α-cyclocitrylideneacetate was successively oxidized with selenium dioxide and chromium trioxide-pyridine complex to give methyl 1′-hydroxy-α-cyclocitrylideneacetate and a mixture of methyl 3′-keto-β-cyclocitrylideneacetate and methyl 4′-keto-α-cyclocitrylideneacetate. Further, oxidation of methyl α-cyclocitrylideneacetate with tert-butyl chromate afforded methyl 4′-keto-α-cyclocitrylideneacetate and methyl 1′-hydroxy-4′-keto-α-cyclocitry-lineacetate. Similarly, methyl α-cyclogeranate was oxidized to methyl 3-keto-β-cyclogeranate and methyl 4-keto-α-cyclogeranate. Methyl l′-hydroxy-4′-keto-α-cyclocitrylideneacetate, methyl l-hydroxy-4-keto-α-cyclogeranate and their related compounds did not show growth inhibitory activities on rice seedlings.     

Studies on Abscisic Acid

Epoxidation of methyl dehydro-β-ionylideneacetates with perbenzoic acid afforded methyl 1′, 2′-epoxy-dehydro-β-ionylideneacetates and then methyl 1′, 2′-, 3′, 4′-di-epoxy-dehydro-β-ionylideneacetates. 1′,2′-Epoxy-dehydro-β-ionone, obtained byepoxidation of dehydro-β-ionone, was treated with carbethoxymethylenetriphenlphosphorane to give ethyl 1′, 2′-epoxy-dehydro-β-ionylideneacetates. Further, sensitive photooxidation of ethyl dehydro-β-ionylidenecrotonate, followed by alkaline hydrolysis, gave 1′-hydroxy-4′-keto-α-ionylidenecrotonic acid. Growth inhibitory activities of the above compounds on rice seedlings were examined.     

Effect of Indoleacetic Acid on the Abscisic Acid Level in Stem Tissue

Excised stem sections from growing plants of Populus tremula L. and Pisum sativum L. including lateral buds were treated with indole-3-acetic acid in a phosphate buffer solution. In control sections the level of the abscisic acid-like inhibitor decreased strongly during 24 h as did the level of the endogenous auxin. Exogenous indoleacetic acid counteracted the decrease in the inhibitor level to a considerable extent. Implications of this auxin effect in relation to apical dominance are discussed.     

Studies on Abscisic Acid

Oxidation of 2-cis-α-ionylidene-ethanol (II) with active MnO₂ afforded a mixture of 2-cis and 2-trans-α-ionylideneacetaldehydes (III and IV). Reduction of methyl epoxy-α- and -β-ionylideneacetates (Vb, Xb XXIb and XXIIb) with LiAlH₄ gave the diols (VI, XI, XXIII and XXIV). The Wittig reaction of the hydroxyketones (XIII and XVIII) with carbethoxymethylenetriphenylphosphorane, followed by alkaline hydrolysis, yielded 5-(1′-and 2′-hydroxy-2′,6′,6′-trimethyl-1′-cyclohexyl)-3-methylpentadienoic acids (XIVa, XVa, XIXa and XXa). The reaction of α-cyclocitrylideneacetaldehyde (XXVII) and dihydro-α-ionone (XXXIII) with carbethoxymethylenetriphenylphosphorane afforded ethyl 3-demethyl-α-ionyli-deneacetate (XXVIIIb) and ethyl dihydro-α-ionylideneacetates (XXXIVb and XXXVb). Physiological activities of the above synthesized compounds on rice seedlings were examined.     

Studies on Abscisic Acid

Photosensitized oxygenation of dehydro-β-ionylidene-ethanol afforded 1′-hydroxy-4′keto-α-ionylidene-ethanol, which was oxidized with active MnO₂ to give 1′-hydroxy-4′-keto-α-ionylidene-acetaldehyde. The Wittig reaction of α-ionylideneacetaldehyde with carbethoxymethylenetriphenylphosphorane or the phosphorane prepared from ethyl γ-bromosenecioate gave ethyl α-ionylidene-crotonate or ethyl α-ionylidenesenecioate. Vitamin A₂ acid ethyl ester was converted to the hydroxy-keto-ester by photosensitized oxygenation. About the above synthesized compounds were examined growth inhibitory activities on rice seedlings.     

Studies on Abscisic Acid

Oxidation of methvl 2-trans-β-ionylideneacetate with X-bromosuccinimide afforded methyl 2-cis and trans-3′-hydroxy-β-ionylideneacetates. NaBH₄ reduction of methyl 2-cis-3′-keto-β-ionylideneacetate and ethyl 4′-keto-α-ionylideneacetate gave methyl 2-cis-3′-hydroxy-β-ionylideneacetate and ethyl 4′-hydroxy-α-ionyiideneacetate respectively. Further, methyl 4′-methoxy-epoxy-α-ionylideneacetate was prepared by epoxidation of methyl 4′-methoxy-α-ionylideneacetate. And then methyl 4′-hydroxy-l′, 2′-dihydro-β-ionylideneacetate was synthesized from ethyl 4-keto-α-cyclogeranate. Growth inhibitory activities of the above compounds on rich seedlings were examined.     

Studies on Abscisic Acid

Methyl α-ionylideneacetates were oxidized with selenium dioxide to a mixture of methyl 3′-keto-β-ionylideneacetates and a small amount of methyl 4′-keto-α-ionylidene-acetates followed by treatment with active manganese dioxide. By a similar oxidation methyl 3′-keto-β-ionylideneacetates were prepared from methyl β-ionylidene acetates. Methyl 4′-keto-α-ionylideneacetates were obtained by oxidation of methyl α-ionylideneacetates with tert-butyl chromate. Dehydrobromination of methyl bromoionylideneacetate, obtained by bromination of methyl 2-trans-α-ionylideneacetate with N-bromosuccinimide, gave a mixture of methyl 2-trans-dehydro-β-ionylideneacetate and methyl 2-cis-dehydro-β-ionylideneacetate. The growth inhibitory activities of these sesquiterpene carboxylic acids and keto esters on rice seedlings were tested.     

脱落酸（ABA） 受体的研究进展

植物激素脱落酸(ABA)在植物对逆境适应及种子发育过程中具有重要的生理功能。尽管ABA作用的分子机制还不清楚,ABA受体还未得到鉴定,但近年来对ABA结合蛋白的研究取得了可喜的进展,已在多种植物中证明存在与ABA有高亲和力的结合蛋白。ABA的识别到底发生在胞外还是胞内,近几年随着微注射技术的应用,也得到不少实验证据。ABA信号的转导途径,特别是位于下游区域参与信号传递的物质的研究取得重大进展,其中以ABA调节气孔保卫细胞开关的信号传递成为研究这一领域的模式体系。     

Ribonucleic Acid Dependent Ribonucleic Acid Replicase in the Immune Response

An immune ribonucleic acid (iRNA) preparation was made using phenol extracts of spleens of mice previously immunized with Salmonella tennessee flagella. An enzyme, also prepared from the spleens of these mice, induced the incorporation of ³H-UTP into the acid-insoluble fraction in a cell-free system in the presence of this RNA. The enzyme activity could be demonstrated from the spleens of immunized mice but not from normal ones, and this activity was also inhibited by two derivatives of rifamycin. Treatment with ribonuclease or heating at alkaline pH resulted in a loss of activity in added RNA. The ³H-uridine-labeled product was found resistant to ribonuclease treatment but became sensitive when the product was subjected to heat treatment. However, actinomycin D, mitomycin C or bleomycin A₂ did not inactivate the enzyme activity. These results suggest that this enzyme induces the incorporation of UTP into the acid-insoluble fraction using iRNA as a template and the product may be a newly synthesized RNA which forms a hybrid with iRNA. This enzyme activity may play a role in the antibody formation process, and may account for the in vivo replication of iRNA by this enzyme, viz., probably an RNA-dependent RNA replicase.     

Effect of Abscisic Acid on the Transpiration of Zea mays

Intact plants of Zea mays L. were treated with foliar sprays of cis-trans-abscisic acid (ABA) at concentrations from 10⁻⁹ to 10⁻⁴M. Even the lowest concentration caused a reduction of the transpiration rate as measured between 1 and 33 h after spraying. With increasing ABA concentrations, there was a nearly linear relationship between the logarithm of the ABA concentration and the (decreasing) transpiration rate within that period. Subsequently a partial recovery of the transpiration rate set in, beginning progressively later as the ABA concentration was increased. After 5 1/2 days the transpiration rate of plants treated with 10⁻⁹ and 10⁻⁸M was nearly back to normal, whereas plants treated with 10⁻⁴M transpiration at only about 2/3 their normal rate. In experiments with detached maize leaves supplied with water or ABA solutions (10⁻⁸ to 10⁻⁵M) through their cut bases, the transpiration of control leaves decreased gradually to a low level in 24 h. ABA caused a marked and rapid reduction of the transpiration rate compared to that of the controls. After a few hours, the transpiration of the treated leaves decreased at a slower rate than that of the controls, thus approaching the control values. After 35 h, the transpiration of leaves treated with 10⁻⁵M ABA was nearly the same as in untreated leaves. Exchanging the ABA solution for distilled water after 24 h had little effect on the subsequent course of the transpiration rate.     

Heterophylly in Ranunculus flabellaris: The Effect of Abscisic Acid on Leaf Ultrastructure

Ranunculus flabellaris Rafin., an aquatic buttercup, exhibitsheterophylly at the level of cellular ultrastructure. Comparedto terrestrial leaves, underwater leaves have thinner epidermalcell walls and more numerous paramural bodies per epidermaland mesophyll cell cross-section. The number of chloroplastsand mitochondria in cell cross-sections also contrasts betweenthe two leaf types. Despite within-and between-leaf variations,different patterns of organelle distribution for the two leafforms were found using principal coordinates analysis. In addition,underwater leaf chloroplasts are smaller, have fewer grana,a greater number of thylakoids/granum, and less starch comparedto chloroplasts from terrestrial leaves. At the ultrastructurallevel, submergence in ABA solution does not produce a leaf withas many characteristics of the terrestrial environment, as shownin previous studies of leaf morphology and anatomy. While numberand distribution of organelles in ABA-treated leaves are similarto terrestrial leaves, some features of chloroplast internalstructure and paramural body number and distribution resembleunderwater leaves. It is postulated that ABA acts as a morphogeninvolved in guiding the irreversible processes of leaf development,but certain subcellular characteristics may be determined directlyby the physical environment. Difficulties encountered in quantitativeanalyses of cellular ultrastructure are discussed. Ranunculus flabellaris, ABA, heterophylly, leaf ultrastructure, principal coordinates analysis     

Heterophylly in Ranunculus flabellaris: The Effect of Abscisic Acid on Leaf Anatomy

Ranunculus flabellaris Raf., the yellow water crowfoot, exhibitsstriking heterophylly between submerged and terrestrial leaves.Leaves produced under water are highly divided with numerousnarrow lobes and deep sinuses, whereas terrestrial leaves havefew broad lobes and shallow sinuses. When plants are submergedin a 25 µM solution of ABA, the typical transition fromterrestrial to submerged leaves is completely suppressed and,instead, terrestrial-like leaves are produced. Image analysistechniques show that, in addition to this modification of leafmorphology, leaves produced under ABA treatment possess surfaceand internal features characteristic of terrestrial leaf anatomy.This study provides evidence that the environmental factorsthat influence the morphological and anatomical expression ofheterophylly may act through endogenous ABA. Ranunculus flabellaris, yellow water crowfoot, ABA, heterophylly, leaf anatomy