Indoleacetic Acid and abscisic Acid antagonism: I. On the phytochrome-mediated attachment of mung bean root tips on glass

The phytochrome-mediated attachment of mung bean (Phaseolus vulgaris L., var. Oklahoma 612) root tips on glass is quickly affected by indoleactic acid and abscisic acid at concentrations of 10 nm or less. Indoleacetic acid induces detachment, whereas abscisic acid induces attachment. Both plant regulators rapidly antagonize the action of the other. None of several cytokinins, gibberellins, and ethylene tested over a wide range in concentration had any effect on either attachment or detachment of root tips. It is postulated that phytochrome could control the endogenous levels of indoleacetic acid and abscisic acid and perhaps other hormones under certain circumstances, that this action is the first process initiated by phytochrome, and that indoleacetic acid and abscisic acid act on the plasmalemma to bring about opposing changes in the surface electric charges of plant cells.     

Indoleacetic Acid and Abscisic Acid Antagonism: II. On the Phytochrome-Mediated Attachment of Barley Root Tips on Glass

The phytochrome-mediated attachment of mung bean (Phaseolus vulgaris L., var. Oklahoma 612) root tips on glass is quickly affected by indoleactic acid and abscisic acid at concentrations of 10 nm or less. Indoleacetic acid induces detachment, whereas abscisic acid induces attachment. Both plant regulators rapidly antagonize the action of the other. None of several cytokinins, gibberellins, and ethylene tested over a wide range in concentration had any effect on either attachment or detachment of root tips. It is postulated that phytochrome could control the endogenous levels of indoleacetic acid and abscisic acid and perhaps other hormones under certain circumstances, that this action is the first process initiated by phytochrome, and that indoleacetic acid and abscisic acid act on the plasmalemma to bring about opposing changes in the surface electric charges of plant cells.     

The role of abscisic acid in plant-pathogen interactions

The effect of the abiotic stress hormone abscisic acid on plant disease resistance is a neglected field of research. With few exceptions, abscisic acid has been considered a negative regulator of disease resistance. This negative effect appears to be due to the interference of abscisic acid with biotic stress signaling that is regulated by salicylic acid, jasmonic acid and ethylene, and to an additional effect of ABA on shared components of stress signaling. However, recent research shows that abscisic acid can also be implicated in increasing the resistance of plants towards pathogens via its positive effect on callose deposition.     

Gas-liquid chromatography of trimethylsilyl derivatives of abscisic Acid and other plant hormones

This paper describes a new method for qualitative and quantitative assay of abscisic acid and other acidic plant hormones, such as indoleacetic acid and the gibberellins, by the gas-liquid chromatography of their trimethylsilyl derivatives. Interfering substances in plant extracts were largely removed by preliminary column chromatography with carbon-celite and elution of the abscisic acid with 60% acetone, permitting direct determination of abscisic acid by gas-liquid chromatography using a flame ionization detector. (A level of 0.65 mg/kg fr wt was found.) This method enables measurement of amounts of abscisic acid as low as 0.025 μg. In impure samples collected by gas-liquid chromatography the abscisic acid recovered could be measured quantitatively by use of its ultraviolet absorption maximum at 260 mμ.     

脱落酸生物合成研究进展

脱落酸作为一种抑制生长的植物激素,是平衡植物内源激素和调节生长代谢的关键因子。脱落酸具有提高作物抗旱耐盐、减少果实褐变的作用,同时可降低疟疾发病率、刺激胰岛素分泌,因此在农业和医药领域有着广阔的应用前景。相较于传统的植物提取法和化学合成法,利用微生物合成脱落酸是一种经济、可持续的来源方式。目前利用天然微生物如灰葡萄孢霉菌、蔷薇色尾孢菌等合成脱落酸的研究已经取得了诸多进展,而脱落酸的异源微生物合成研究相对较少。酿酒酵母、解脂耶氏酵母、大肠杆菌等工程菌株作为天然产物异源合成的常用宿主,具有遗传背景清晰、易于操作、便于工业化生产等优势,因此利用微生物异源合成脱落酸是一种更具潜力的生产方式。本文着重从底盘细胞的选择、关键酶的筛选与表达强化、辅因子的调节、增强前体供应及促进脱落酸外排5个方面对微生物异源合成脱落酸的研究进行综述。最后,对该领域的未来发展方向进行了展望。     

The directional control of sucrose and asparagine transport in lupin by abscisic acid

Injections of exogenous abscisic acid into the primary flowerhead of Lupinus luteus cv. Weiko III reduced the movement of ¹⁴C-sucrose into the flowerhead from the uppermost leaves. Sucrose transported from below the lateral branches subtending the flowerhead, was diverted into the lateral branches by injection of the exogenous abscisic acid into the flowerhead. ¹⁴C-sucrose was also diverted from a lateral branch injected with exogenous abscisic acid to all other parts of the plant, particularly the main stem and leaves, and the roots. Transport of ¹⁴C-asparagine administered at the cotyledonary node was directed from the flowerhead into the subtending lateral branches by injection of abscisic acid into the flowerhead. Transport of both ¹⁴C-sucrose and ¹⁴C-asparagine into the flowerhead was reduced at least three fold at physiological levels of abscisic acid. No significant correlation was found between the amount of ¹⁴C-asparagine entering a sink and the dry weight of the tissues of that sink. It is concluded that distribution of ¹⁴C-sucrose and ¹⁴C-asparagine between the flowerheads and lateral branches of L. luteus is actively and dynamically controlled and that abscisic acid levels play a significant part in that control. It is suggested that the relative levels of endogenous abscisic acid in plant organs could serve as an important factor in the directional control of assimilate transport in plants.     

Expression of a single-chain Fv antibody against abscisic acid creates a wilty phenotype in transgenic tobacco

The plant hormone abscisic acid (ABA) participates in the control of several important physiological processes in plants such as stomata regulation, seed dormancy and stress tolerance. A new strategy was developed to study these phenomena by blocking abscisic acid with intracellularly expressed specific single-chain variable fragment (scFv) antibodies. Here evidence is presented that the expression of single-chain Fv antibodies against abscisic acid in the endoplasmic reticulum of transgenic tobacco cells leads to a wilty phenotype. Stomatal conductance is increased at high CO₂ concentrations dependent on the level of antibody expression in leaves. Symptoms of abscisic acid deficiency were generated in the transformants although they have even higher levels of abscisic acid than wild-type plants.     

A Rapid and Simple Radioassay for Abscisic Acid using 14C-Diazomethane

A simple physical method for measuring abscisic acid concentrationin plant material is described. Abscisic acid in partially purifiedextracts was radiolabelled by reaction with ¹⁴C-diazomethaneto give ¹⁴C-methyl abscisate, which was purified from otherradiolabelled products by thin layer chromatography. Abscisicacid concentration was measured by comparison of the ¹⁴C radioactivityincorporated into plant abscisic acid with that in standard¹⁴-C-methyl abscisate prepared under the same conditions fromknown amounts of pure abscisic acid. Losses of abscisic acidwhich occurred during purification were corrected by measuringthe recovery of ³H-abscisic acid added to initial extracts. Abscisic acid concentration was measured by radioassay and byconventional electron capture-gas chromatography in oat, bean,and turgid or wilted tobacco leaves. Results from the two methodswere closely comparable. Radioassay is as rapid and sensitiveas existing procedures for measuring abscisic acid, but requiresonly simple and inexpensive chromatographic equipment.     

A comparison of some methods for the purification of abscisic acid and its metabolites from plants extracts

The use of small columns containing charcoal and cellulose for the purification of abscisic acid and its metabolites from plant extracts is described. These columns have high capacity and the sample processing time is short. The efficiencies of recovery of abscisic acid, abscisic acid glucose ester, dihydrophaseic acid and an unidentified highly polar metabolite of abscisic acid are about 90%. The method is shown to be superior to other published methods using commercial pre-packed cartridges.     

An enzyme-immunoassay for cis-(+)-abscisic acid

A solid-phase enzyme-immunoassay for abscisic acid and abscisic acid conjugates in fmol amounts (detection limit ca 50–60 fmol) has been developed. Only little procedural effort is required for the assay which can be completed within 6 h. With this method, abscisic acid was detected in a range of heterotrophically growing plant suspension cultures. In addition, abscisic acid-glucosyl ester was identified in a Lonicera prolifera Rehd. tissue culture. In this tissue, the level of free abscisic acid reaches ca 2 × 10⁻⁶ M in the late log-phase of growth.     

Developing a model of plant hormone interactions

Plant growth and development is influenced by mutual interactions among plant hormones. The five classical plant hormones are auxins, cytokinins, gibberellins, abscisic acid and ethylene. They are small diffusible molecules that easily penetrate between cells. In addition, newer classes of plant hormones have been identified such as brassinosteroids, jasmonic acid, salicylic acid and various small proteins or peptides. These hormones also play important roles in the regulation of plant growth and development. This review begins with a brief summary of the current findings on plant hormones. Based on this knowledge, a conceptual model about interactions among plant hormones is built so as to link and develop an understanding of the diverse functions of different plant hormones as a whole in plants.Key words: abscisic acid, auxin, brassinosteroids, cytokinins, ethylene, gibberellins, jasmonic acid, salicylic acid, plant peptide hormones     

The effect of plant hormones on the components of the secretory pathway in human normal and tumor cells

Plant hormones play a key role in plant growth and differentiation. Certain plant hormones are known to be potential antitumor agents, affect the secretory activity of animal cells, and are produced by mammalian cells as proinflammatory cytokines. The goal of this research was to study the effect of abscisic and gibberellic acids on the secretory system of human epidermoid A431 carcinoma cells and HaCaT keratinocytes. Immunocytochemical and morphometric analysis showed that a subtoxic concentration of abscisic and gibberellic acids induced extension of the ER network and increased the size of the Golgi complex. Electron-microscope studies confirmed the hypertrophic changes of the Golgi complex: swelling of cisternae in the trans-Golgi compartment after exposure to abscisic acid and swelling of cis- and trans-compartments after exposure to gibberellic acid. The Click-iT technique revealed elevation of total protein synthesis only in A431 cells exposed to abscisic acid. Our data suggest that the hypertrophy of Golgi may reflect enhanced secretory activity in A431 cells exposed to abscisic acid. In other experiments, Golgi hypertrophy was not accompanied with increased protein synthesis that suggested the stress-related changes of ER and Golgi complex. Our results demonstrate that morphologically similar reaction manifested in hypertrophy of Golgi complex, in response to plant hormones, is the result of different functional activities, and that molecular mechanisms underlying induced changes need further investigations.     

Sugar and hormone connections

Sugars modulate many vital processes that are also controlled by hormones during plant growth and development. Characterization of sugar-signalling mutants in Arabidopsis has unravelled a complex signalling network that links sugar responses to two plant stress hormones--abscisic acid and ethylene--in opposite ways. Recent molecular analyses have revealed direct, extensive glucose control of abscisic acid biosynthesis and signalling genes that partially antagonizes ethylene signalling during seedling development under light. Glucose and abscisic acid promote growth at low concentrations but act synergistically to inhibit growth at high concentrations. The effects of sugar and osmotic stress on morphogenesis and gene expression are distinct. The plasticity of plant growth and development are exemplified by the complex interplay of sugar and hormone signalling.     

脱落酸、胁迫、成熟诱导基因研究进展

近年来从植物中发现了越来越多的受脱落酸、胁迫、成熟诱导表达的基因,这些 ASR(Abscisic acid, Stress and Ripening inducible)基因参与植物对冷、渗透压、脱落酸处理的胁迫应答已被证实,该类基因也参与植物生命活动的许多方面如果实发育、成熟等．对 ASR 基因的克隆鉴定,以及该基因在胁迫应答和果实成熟方面的作用进行了综述．     

Effect of High Air Temperature on Cytokinins and Abscisic Acid Contents as Well as Water Balance in Wheat Seedlings

The contents of cytokinins and abscisic acid in the shoots and roots of 8-day wheat seedlings were studied by enzyme immunoassay in conditions of heating from 24 to 35°C and after returning to the initial conditions. Two peaks of abscisic acid content in the aerial plant organs accompanied by decreased content of the active cytokinin (zeatin) were observed at the beginning and at the end of heating. We propose that antiphase changes in zeatin and abscisic acid concentrations should enhance the same effects, for example, stomatal closure.     

Deuterium-labeled Phaseic Acid and Dihydrophaseic Acids for Internal Standards

The concentration of abscisic acid in plants is regulated not only by biosynthesis, but also by metabolism. Abscisic acid is metabolized to phaseic acid via 8′-hydroxyabscisic acid, and phaseic acid is then converted to dihydrophaseic acid and its epimer. A quantitative analysis of these metabolites is important as well as that of abscisic acid to understand changes in the concentration of abscisic acid in plants. However, no internal standards of the metabolites suitable for quantitative analysis have been reported. We prepared 7′-deuterium-labeled phaseic acid with a deuterium content of 86%, using the equilibrium reaction between phaseic acid and 8′-hydroxyabscisic acid. 7′-Deuterium-labeled dihydrophaseic acids were obtained by reducing 7′-deuterium-labeled phaseic acid. The levels of the metabolites in plant organs were determined by using the deuterated metabolites as internal standards.     

Deuterium-labeled phaseic acid and dihydrophaseic acids for internal standards

The concentration of abscisic acid in plants is regulated not only by biosynthesis, but also by metabolism. Abscisic acid is metabolized to phaseic acid via 8'-hydroxyabscisic acid, and phaseic acid is then converted to dihydrophaseic acid and its epimer. A quantitative analysis of these metabolites is important as well as that of abscisic acid to understand changes in the concentration of abscisic acid in plants. However, no internal standards of the metabolites suitable for quantitative analysis have been reported. We prepared 7'-deuterium-labeled phaseic acid with a deuterium content of 86%, using the equilibrium reaction between phaseic acid and 8'-hydroxyabscisic acid. 7'-Deuterium-labeled dihydrophaseic acids were obtained by reducing 7'-deuterium-labeled phaseic acid. The levels of the metabolites in plant organs were determined by using the deuterated metabolites as internal standards.     

Development of Agrobacterium tumefaciens C58-induced plant tumors and impact on host shoots are controlled by a cascade of jasmonic acid,auxin, cytokinin,ethylene and abscisic acid

The development of Agrobacterium tumefaciens-induced plant tumors primarily depends on the excessive production of auxin and cytokinin by enzymes encoded on T-DNA genes integrated into the plant genome. The aim of the present study was to investigate the involvement of additional phytohormone signals in the vascularization required for rapid tumor proliferation. In stem tumors of Ricinus communis L., free auxin and zeatin riboside concentrations increased within 2 weeks to 15-fold the concentrations in control stem tissue. Auxin and cytokinin immunolocalization revealed the highest concentrations within and around tumor vascular bundles with concentration gradients. The time-course of changes in free auxin concentration in roots was inversely correlated with that in the tumors. The high ethylene emission induced by increased auxin- and cytokinin correlated with a 36-fold accumulation of abscisic acid in tumors. Ethylene emitted from tumors and exogenously applied ethylene caused an increase in abscisic acid concentrations also in the host leaves, with a diminution in leaf water vapor conductance. Jasmonic acid concentration reached a maximum already within the first week of bacterial infection. A wound effect could be excluded. The results demonstrate the concerted interaction of a cascade of transiently induced, non-T-DNA-encoded phytohormones jasmonic acid, ethylene and abscisic acid with T-DNA-encoded auxin and zeatin riboside plus trans-zeatin, all of which are required for successful plant tumor vascularization and development together with inhibition of host plant growth.     

Aspects of the Effect of ABA on the Water Status of Barley and Wheat Seedlings

The effect of abscisic acid on plant growth and survival during water deprivation was studied in barley and wheat seedlings. Under conditions of both limited and ample water supply, treatment with abscisic acid greatly reduced transpiration and, in addition, suppressed root growth. In water-deprived seedlings, abscisic acid increased the total dry matter, reflecting improved efficiency in water-use. In addition, the growth period and survival of water-deprived seedlings were markedly prolonged. In field trials, however, abscisic acid had no significant effect on waterdeprived seedlings. Possible reasons for this lack of response are discussed.