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PubMed1968

Studies on the role of RNA synthesis in auxin induction of cell enlargement.

Selective inhibitors were used to study the connection between nucleic acid synthesis and indoleacetic acid (IAA) induction of cell enlargement. Actinomycin D (act D) and azaguanine (azaG) almost completely inhibit IAA-induced growth in aged artichoke tuber disks when they are added simultaneously with IAA. In contrast, when they are added 24 hours after the hormone, these inhibitors have little or no effect on the induced growth which continues for 48 hours or more with little or no inhibition. Inhibitors of protein synthesis still stop growth when applied 24 hours after the IAA, thus protein synthesis and presumably supporting metabolism are still essential.In corn coleoptile sections auxin-induced growth did not show any pronounced tendency to become less sensitive to act D as the IAA treatment progressed. Act D did not completely inhibit the response to IAA unless the sections were pretreated with act D for 6 hours. In contrast to act D, cordycepin produced almost complete inhibition of IAA-induced growth when added with the IAA.Although IAA has a very large and very rapid stimulatory effect (within 10 min) on incorporation of (32)P-orthophosphate into RNA in disks, it did not cause a detectable change in the base composition of the RNA synthesized. Furthermore, the promotive effect could be accounted for through increased uptake of the (32)P. That much of the RNA synthesis in these tissues is not necessary for auxin action is indicated by the results with fluorouracil (FU). FU strongly inhibits RNA synthesis, probably acting preferentially on ribosomal RNA synthesis, without inhibiting auxin-induced growth in the disks or coleoptile sections. FU also strongly inhibited respiration in auxin-treated disks indicating that the large promotion of respiration by auxin likewise may not be entirely necessary for growth.At least in the artichoke disks, RNA synthesis is required for auxin induction of cell enlargement and not for cell enlargement itself.The possible relationships of auxin induction of cell enlargement and RNA synthesis are discussed.

Journal Article↗

PubMed1986

Phloem unloading in soybean seed coats: dynamics and stability of efflux into attached ;empty ovules'.

The time-course of sucrose efflux from attached seedcoats (having their embryos surgically removed) into aqueous traps placed in the ;empty ovules' had three phases. The first phase lasted 10 minutes and probably was a period of apoplastic flushing. The second lasted 2 to 3 hours and is thought to be a phase of equilibration of seed coat symplast with the frequently refreshed liquid. The third phase of relatively steady efflux was postulated to reflect the continued import of sucrose from the plant, and hence to reflect the rate of sieve tube unloading. The average steady state efflux was equal under most conditions to the estimated rate of sucrose import. Efflux and import were unaffected by 150 millimolar osmoticum (mannitol or polyethylene glycol [molecular weight about 400]), by 0.5 millimolar CaCl(2), or by pretreatments up to 20 minutes with p-chloromercuribenzenesulfonic acid (PCMBS); they were enhanced by 40 micromolar abscisic acid, 40 micromolar indoleacetic acid, 20 micromolar fusicoccin, and 1 millimolar dithiothreitol (DTT) and were inhibited by 100 micromolar KCN, by 0.03% H(2)O(2), by 20 micromolar and 5 micromolar trifluoromethoxy (carbonyl cyamide) phenylhydrazone, by repeated 5 minutes per hour treatments with 5 millimolar PCMBS, and by 5 millimolar DTT. The ;steady state' sucrose efflux was able to account for about half the rate of dry weight growth of the embryo, but stabilization of the system with <1 millimolar DTT taken together with other considerations is likely to give good correspondence between experimental unloading rates and in vivo growth rates.

Journal Article↗

PubMed1991

In Plant Protoplasts, the Spontaneous Expression of Defense Reactions and the Responsiveness to Exogenous Elicitors Are under Auxin Control.

When auxin was omitted during either the preparation or the culture of tobacco mesophyll protoplasts, as well as during both periods, synthesis of beta-glucanase was spontaneously induced. In contrast, when protoplasts were prepared and cultured in the presence of 16 micromolar 1-naphthaleneacetic acid (optimal concentration for protoplast division), the expression of beta-glucanase was maintained close to the minimal level observed in tobacco leaves. This inhibitory effect was only promoted by active auxins (1-naphthaleneacetic acid, 2,4-dichlorophenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid, and 3-indoleacetic acid) but not by inactive auxin analogs. Tobacco protoplasts responded to exogenous elicitors from the cell wall of Phytophthora megasperma glycinea (Pmg) by accumulating beta-glucanase in the presence of 16 micromolar 1-naphthaleneacetic acid. At higher auxin concentrations, the elicitor-induced beta-glucanase synthesis was inhibited. Naphthaleneacetic acid concentration (3 x 10(-5) molar) required to inhibit by 50% the expression of this defense reaction triggered by a near-optimal elicitor concentration was about 100 times higher than that sufficient to inhibit by 50% the spontaneous expression in nonelicited protoplasts. This is the first demonstration of an auxin-fungal elicitor interaction in the control of a defined defense reaction. The above observations were extended to soybean cell protoplasts. The Pmg elicitor-induced stimulation of the synthesis of pathogenesis related P17 polypeptides and of a 39-kilodalton peptide immunologically related to tobacco beta-glucanase was only observed when the spontaneous accumulation of these proteins was inhibited in auxin-treated protoplasts.

Journal Article↗

PubMed2006

Nitrogen-fixing chemo-organotrophic bacteria isolated from cyanobacteria-deprived lichens and their ability to solubilize phosphate and to release amino acids and phytohormones.

AIMS: Cyanobacteria-deprived lichens of the species Canoparmelia caroliniana, Canoparmelia crozalsiana, Canoparmelia texana, Parmotrema sancti-angeli and Parmotrema tinctorum were screened for the presence of chemo-organotrophic nitrogen-fixing bacteria. METHODS AND RESULTS: Fifty-three lichen samples subjected to enrichment selection using a nitrogen-free minimal medium were positive for acetylene reduction. Seventeen isolates, able to fix nitrogen, belonged to Gamma-proteobacteria group and were identified as: Acinetobacter sp., Pantoea sp., Pseudomonas sp., Pseudomonas stutzeri, Serratia marcescens and Stenotrophomonas maltophilia, according to 16S rRNA gene sequences and biochemical tests. The excretion of amino acid and phytohormone and the ability of mineral phosphate solubilization were determined in 14 isolates. All isolates were able to release amino acids and 3-indoleacetic acid. About 64% of the isolates solubilized phosphates and 30% released ethylene. CONCLUSIONS: These data confirm sparse evidence from the literature on the occurrence of chemo-organotrophic nitrogen-fixing bacteria in cyanobacteria-deprived lichens; the isolates presented physiologic features which might benefit the host if they are expressed when the bacteria are harboured by lichens. SIGNIFICANCE AND IMPACT OF THE STUDY: Chemo-organotrophic nitrogen-fixing bacteria were isolated from a high percentage (72.6%) of cyanobacteria-deprived lichens. All isolates presented important physiological characteristics, some of which are being described here for the first time.

Amino Acids↗

PubMed1975

Applications of gas chromatography and mass spectrometry in neurochemical studies: determination of indole amine profiles at the picogram level.

Work is presented on the application of sensitive and specific analytical methods for the simultaneous assay of tryptophan and its indolic metabolites (5-hydroxytryptophan, serotonin, 5-hydroxy-indole-acetic acid, tryptamine and indoleacetic acid). Due to their small concentrations in selected areas of the central nervous system, suitable derivatives have been prepared for separation by Gas Chromatography (GC) and detection by electron capture (ECD). Carboxylic acid groups have been methylated with BCl3-methanol and phenolic and amine groups have been acylated to pentafluoropropionyl derivatives. This type of derivatives allow a detectability limit of 5 picograms (5 x 10(-12) gr) if the corresponding reaction kinetics and yields are properly optimized. Response curves are presented. Identifications have been obtained by combined GC-MS and by the use of Kovats indeces in two GC stationary phases. The GC separation of the six compounds indicated above can be performed in less than 5 minutes with quantitative reproducibility. This work opens the possibility of performing comparative studies ("screening") of various physiological and pathological conditions by detecting any changes in the profile representative of a whole metabolic pathway, such as that of the indolic compounds in this case.

Chromatography, Gas↗

PubMed1997

Effect of phytohormones on ATP-dependent accumulation of Ca2+ in plasma membrane vesicles from tubers of potato Solanum tuberosum L.

A membrane fraction enriched with plasmalemma vesicles was isolated from potato tubers using the polyethylene glycol 3550--dextran T-500 phase partitioning. As judged by the activities of enzyme markers of the inner plant cell membranes, the fraction consisted of plasmalemma vesicles with tonoplast vesicle contamination and contained no mitochondrial membranes, endoplasmic reticulum or Golgi apparatus. Under conditions of total inhibition of nitrate-sensitive ATPase of the tonoplast, the vesicles of the fraction obtained exhibited the ATP-dependent accumulation of Ca2+. It was inhibited to various extents by Na3VO4, dicyclohexyl carbodiimide (DCCD) and phytohormones--gibberellic acid (GA3), abscisic acid (ABA) and indoleacetic acid (IAA), whereas kinetin rendered a stimulating effect. The action of phytohormones on the accumulation of Ca2+ in the presence of DCCD or Na3VO4 suggests that GA3, ABA and kinetin affect the activity of Ca2+,Mg(2+)-ATPase, whereas IAA most probably stimulates the efflux of Ca2+ from the vesicles or the separation of membrane-bound Ca2+.

Adenosine Triphosphatases↗

PubMed1965

Hormone-induced stabilization of soluble RNA in pea-stem tissue.

When indoleacetic acid labeled with carbon-14 in the carboxyl group is fed to excised green pea-stem segments, growth is initiated, and there is a parallel progressive labeling of the RNA extracted by cold phenol. The bulk of the label is found in the 4S fraction. This fraction is more resistant to degradation by ribonuclease than a similar fractian obtained from tissue not treated with indoleacetic acid.

Carbon Isotopes↗

PubMed1986

Profiling of endogenous ligand solutes that bind to serum proteins in sera of patients with uremia.

The profiling of endogenous ligand solutes in sera of patients with uremia was performed by using an ultrafiltration device and high-performance liquid chromatography. Seventeen endogenous ligand solutes, which are ultraviolet-absorbing substances, were detected in a sample volume of 40 microliters, and four ligand solutes were tentatively identified as indoxylsulfate, hippuric acid, 2-hydroxybenzoylglycine, and 3-indoleacetic acid. One of these ligand solutes designated as peak P was thought to be a candidate for a major drug-binding inhibitor in uremia.

Blood Proteins↗

PubMed1970

Ontogeny and hormonal control of polyphenoloxidase isozymes in tobacco pith.

Isozymes of tobacco pith polyphenoloxidases (o-diphenol oxidase, EC 1.10.3.1) were separated electrophoretically from fresh pith of intact plants and from cultured pith sections. Extracts of fresh pith contained a poorly resolved complex of two to three anodic bands after starch gel electrophoresis at alkaline pH. This anodic complex was more active with chlorogenic acid than with 3,4-dihydroxyphenylalanine and was found in greater activity per gram fresh weight of tissue in younger internodes than in older ones. The longitudinal gradient of activity was thus the opposite of that found for the constitutive isozymes of peroxidase.A well defined cathodic band of polyphenoloxidase activity appeared after culture of pith in modified White's medium with shaking. This band, which was more active with 3,4-dihydroxyphenylalanine than with chlorogenic acid, could be detected after 1 to 2 days of incubation. Its appearance was enhanced by the addition of 10 mum indoleacetic acid; kinetin (1 mum tended to prevent this indoleacetic acid effect). Such hormonal control is opposite to that previously reported for the rapidly appearing new isozymes of peroxidase. The pattern of the major isozymes associated with polyphenoloxidase activities differs from that of peroxidase.

Catechol Oxidase↗

PubMed1974

Red light enhancement of the phototropic response of etiolated pea stems.

In the subapical third internode of 7-day-old etiolated pea seedlings, the magnitude of phototropic curvature in response to continuous unilateral blue illumination is increased when seedlings are pre-exposed to brief red light. The effect of red light on blue light-induced phototropism becomes manifest maximally 4 or more hours after red illumination, and closely parallels the promotive action of red light on the elongation of the subapical cells. Ethylene inhibits phototropic curvature by an inhibitory action on cell elongation without affecting the lateral transport of auxin. Pretreatment of seedlings with gibberellic acid causes increased phototropic curvature, but experiments using (14)C-gibberellic acid indicate that gibberellic acid itself is not laterally transported under phototropic stimuli. Neither red light nor gibberellic acid treatment has any promotive effect on blue light-induced lateral transport of (3)H-indoleacetic acid. Under conditions where phototropic curvature is increased by red light treatment, low concentrations of indoleacetic acid applied in lanolin paste to the apical cut end of the seedling cause an increased elongation response in subapical tissue. This could explain increased phototropic curvature caused by red light treatment.

Journal Article↗

PubMed2006

Effects of indoxylsulfate on the in vitro hepatic metabolism of various compounds using human liver microsomes and hepatocytes.

BACKGROUND: Alterations of hepatic drug metabolism in patients with renal failure are poorly understood. In this study, the effects of uremic substances that can be removed by hemodialysis on in vitrohepatic drug metabolism were studied using human liver microsomes and hepatocytes. METHODS: The metabolism of various compounds that undergo oxidation and glucuronidation in the liver was studied using human liver microsomes and hepatocytes in the presence of 11 uremic substances removable by hemodialysis. RESULTS: The formation of resorufin from ethoxyresorufin was inhibited by 3-indoxylsulfate and 3-indoleacetic acid. The formation of 6beta-hydroxytestosterone from testosterone was inhibited only by 3-indoxylsulfate. These uremic substances reduced the maximum metabolic rate but not the affinity, suggesting that the inhibitory mechanism was noncompetitive. The inhibition of formation of resorufin and 6beta-hydroxytestosterone by 3-indoxylsulfate was also observed in human hepatocytes. The elimination of nicardipine in liver microsomes was decreased significantly in the presence of 3-indoxylsulfate and 3-indoleacetic acid. CONCLUSION: The hepatic metabolism of certain drugs may be inhibited directly by uremic substances such as 3-indoxylsulfate that accumulate in the plasma in patients with chronic renal failure.

Biomarkers↗

PubMed1973

Morphogenesis in selaginella: auxin transport in the stem.

Selaginella willdenovii Baker is a prostrate vascular cryptogam with a dorsiventral stem. At each major branching of the stem apex a dorsal and a ventral angle meristem is formed. The ventral meristem becomes determined as a root, and the dorsal meristem as a shoot. The present investigation examined the distribution and transport of (14)C-indoleacetic acid through stem tissues as a basis for the pattern of meristem determination. Externally applied indoleacetic acid is transported into receiver blocks with a velocity of 12 millimeters per hour. Much of the auxin becomes immobilized in the tissue and is not transported. The polar ratio of auxin transport is approximately 2. Auxin is transported equally on the dorsal and the ventral sides of the stem axis, and the auxin flux in vascular tissue is twice that in the cortex. In the branch junctions twice as much auxin is transported on the dorsal side as on the ventral side, and this is held to be the consequence of the lateral branch vascular tissue connecting with the dorsal and median, but not with the ventral vascular strand of the stem axis.

Journal Article↗

PubMed1976

Adsorption of tryptophan metabolites from physiological fluids on XAD-2 and determination by single ion monitoring.

Endogenous tryptamine, 5-hydroxytryptamine, indoleacetic acid, 5-hydroxyindoleacetic and tryptophan have been recovered from urine and cerebro-spinal fluid by adsorption on XAD-2 resin (0.3 g). After adsorption of the sample on the resin, desorption with methanol provides a single fraction that contains all of these metabolites. The mass spectra of their pentafluoropropionyl derivatives show prominent ions at m/e 276 and 438 which are characteristic of indoles and 5-hydroxyindoles, respectively, a feature that allows the concurrent determination of all the components of each group by functional group analysis. A method has been developed to carry out single ion monitoring with the peak matching system of an Hitachi RMU-6H mass spectrometer. Identifications are based on the respective Kovats Indices and single ion monitoring of two characteristic ions per compound: tryptophan (m/e 276 and 347); tryptamine (m/e 276 and 289); indoleacetic acid (m/e 276 and 335); 5-hydroxytryptamine (m/e 438 and 451); 5-hydroxyindoleacetic acid (m/e 438 and 497). The method described illustrates the feasibility of assaying biogenic indoleamines and acidic metabolites, as well as their precursor amino acid on a single fraction in contrast to other standard fractionation methods. This is possible even if the mass spectrometer is not equipped with an alternating voltage accelerator provided that it has a peak matcher, although the lack of an alternating voltage accelerator requires two separate injections of the same sample, for quantification and identification; one for the indole profile and another for the 5-hydroxyindole profile. Both profiles can be verified by individual monitoring of the other confirmatory ions. With this method the use of a multiple ion detector would allow a simultaneous determination of all of these metabolites in one gas chromatograph mass spectrometer run.

Adsorption↗

PubMed1989

Gravitropism in higher plant shoots. VI. Changing sensitivity to auxin in gravistimulated soybean hypocotyls.

Although the Cholodny-Went model of auxin redistribution has been used to explain the transduction phase of gravitropism for over 60 years, problems are apparent, especially with dicot stems. An alternative to an auxin gradient is a physiological gradient in which lower tissues of a horizontal stem become more sensitive than upper tissues to auxin already present. Changes in tissue sensitivity to auxin were tested by immersing marked Glycine max Merrill (soybean) hypocotyl sections in buffered auxin solutions (0, 10(-8) to 10(-2) molar indoleacetic acid) and observing bending and growth of upper and lower surfaces. The two surfaces of horizontal hypocotyl sections responded differently to the same applied auxin stimulus; hypocotyls bent up (lower half grew more) in buffer alone or in low auxin levels, but bent down (upper half grew more) in high auxin. Dose-response curves were evaluated with Michaelis-Menten kinetics, with auxin-receptor binding analogous to enzyme-substrate binding. Vmax for the lower half was usually greater than that for the upper half, which could indicate more binding sites in the lower half. Km of the upper half was always greater than that of the lower half (unmeasurably low), which could indicate that upper-half binding sites had a much lower affinity for auxin than lower-half sites. Dose-response curves were also obtained for sections scrubbed' (cuticle abraded) on top or bottom before immersion in auxin, and gravitropic memory' experiments of L. Brauner and A. Hagar (1958 Planta 51: 115-147) were duplicated. [1-14C]Indoleacetic acid penetration was equal into the two halves, and endogenous plus exogenously supplied (not radiolabeled) free auxin in the two halves (by gas chromatography-selected ion monitoring-mass spectrometry) was also equal. Thus, differential growth occurred without free auxin redistribution, contrary to Cholodny-Went but in agreement with a sensitivity model.

Dose-Response Relationship, Drug↗

PubMed1975

The Effect of Indole-3-acetic Acid and Other Growth Regulators on the Ripening of Avocado Fruits.

Observations were made of the effects of several plant regulators, indole-3-acetic acid, kinetin, abscisic acid, and gibberellic acid, as well as of extracts prepared from leaves and fruit stalks on the respiration pattern, ethylene production, and the number of days to ripen of avocado fruits (Persea americana Mill.). These substances were vacuum infiltrated to insure good penetration and distribution. Kinetin, abscisic acid, gibberellic acid, and the extracts had no effect on either ripening time or on the respiration pattern and ethylene production of the fruits. Indoleacetic acid, however, had a marked effect on ripening. At high concentrations (100 and 1000 mum), indoleacetic acid stimulated respiration and induced preclimacteric ethylene production, resulting in accelerated ripening of the fruits. At the low concentrations (1 and 10 mum), it delayed ripening of fruits and suppressed the climacteric respiration and ethylene production. The results reinforce several previous observations with other fruits that auxins may largely constitute ;resistance to ripening' and may be responsible for the lack of ripening shown by unpicked fruits.

Journal Article↗

PubMed1993

Low selenium diet affects monoamine turnover differentially in substantia nigra and striatum.

Turnover of dopamine, noradrenaline, serotonin, and their metabolites has been measured in striatum and substantia nigra of adult female rats that were fed control or selenium-deficient diets for 15 days. In addition, the glutathione peroxidase activity has been studied. The most striking result was the increase of dopamine turnover (63%) and 3-methoxytyramine turnover (55%) in substantia nigra between control and experimental animals. On the other hand, no changes were found in the turnover rate of dopamine and its metabolites in the striatum. Likewise, no changes were found in noradrenaline turnover in substantia nigra. In the striatum, there was a significant increase of serotonin turnover versus no change for 5-hydroxy-3-indoleacetic acid. However, in the substantia nigra, serotonin turnover did not show significant changes, whereas 5-hydroxy-3-indoleacetic acid turnover decreased. At the same time, glutathione peroxidase activity significantly decreased in both structures after selenium-deficient diets. These results suggest that a selenium-deficient diet for a short period of time decreases brain protection, principally in the substantia nigra, against oxidative damage.

Animals↗

PubMed1982

Growth and metabolic activity of lemon juice vesicle explants in vitro.

Actively growing juice-vesicle explants, established from small lemon (Citrus limon L. Burm. f. var. ;Eureka') fruits, were cultured in vitro on defined media. The juice vesicles continued to enlarge in culture for several months, without callus proliferation, and their initial growth was promoted by indoleacetic acid, gibberellic acid, and N(6)-benzyladenine.The metabolic competence of the explants, and its relevance to whole fruit development, was further investigated. Juice vesicles continued to accumulate protein on all media, for at least 16 days, but sugars did not change much during culture. Acid invertase increased dramatically during the first days of culture, and its specific activity was markedly promoted by indoleacetic acid, and to a lesser degree by gibberellic acid. Total peroxidase of juice vesicles increased progressively up to the 11th day of culture, and its specific activity was promoted by all three hormones, especially by N(6)-benzyladenine. Explant growth was accompanied by appearance of several cathodic and anodic isoperoxidases.The results suggest that the study of this unique juice vesicle system may contribute to a better understanding of fruit development.

Journal Article↗

PubMed1977

In vitro formation and development of floral buds on tobacco stem explants: effects of kinetin and other factors.

Stem segments were excised from plants of Wisconsin 38 tobacco (Nicotiana tabacum L.) in three regions differing in their distance below the inflorescence. They were cultured in vitro in 8- or 16-hr days. After 8 weeks, floral and vegetative buds were counted, and extent of floral development was assessed. Kinetin at 10(-5)m inhibited formation and development of floral buds regardless of indoleacetic acid concentration. Supplied at this concentration with adequate auxin, kinetin stimulated vegetative bud formation and may have caused floral bud abortion. Indoleacetic acid (>/= 10(-6)m) inhibited vegetative and floral bud formation when supplied with low kinetin concentration (</= 10(-7)m) but did not affect floral development. When supplied with high kinetin concentration (>/= 10(-6)m), it inhibited floral bud formation and stimulated vegetative bud formation. More floral buds were formed in 16-hr days than in 8-hr days. Few formed on explants other than those derived from the region nearest the inflorescence regardless of other treatment.

Journal Article↗