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.     

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。     

Chemistry of Abscisic Acid, Abscisic Acid Catabolites and Analogs

Recently there have been breakthroughs on a number of fronts in abscisic acid (ABA) biology research that have advanced the field significantly, including discovery of genes involved in ABA metabolism, along with progress in understanding of ABA signaling (Finkelstein and others 2002; Kushiro and others 2004; Lim and others 2005; Saito and others 2004). At the same time, the chemistry of ABA has advanced. New analytical methods have been developed for profiling ABA and catabolites (Ross and others 2004; Zaharia and others 2005). Novel bioactive catabolites have been discovered from feeding studies with deuterated ABA and catabolites (Zaharia and others 2004; Zhou and others 2004). This review covers recent advances and prospects in natural products chemistry, analysis of ABA catabolism, and applications of ABA analogs for biochemical studies and horticultural uses.     

Abscisic Acid Translocation and Influence of Water Stress on Grain Abscisic Acid Content

The movement of foliar applied [1-¹⁴C]abscisic acid (ABA) inwheat plants (Triticum aestivum L., cv. Kolibri) was investigatedat two stages of grain development (1000 grains, weight 19 and24 g dry matter). [1–¹⁴C]ABA seemed to be readily translocated within 12h into the developing grains as well as in other plant parts.A subsequent rapid metabolism took place leading to a decreasedactivity of the ABA-containing chromatogram fraction in theyounger plants 48 h after application. The metabolism seemodto be less intensive in the older grains, where the activityrunning with the ABA increased over 64 h. Treating the leaves of barley plants (Hordeum vulgare, L., cv.Union) 2 weeks after anthesis with a gentle stream of warm air(36° C) resulted in a significant increase in the ABA contentof all parts of the ear. The results mentioned above indicatethat this may be partially due to translocation from other partsof the plant such as the leaves.     

植物ABA受体及其介导的信号转导通路

ABA是调控植物体生长发育和响应外界应激的重要植物激素之一。近年来, ABA受体的筛选和鉴定取得了突破性进展, 为植物中ABA信号转导通路的阐明奠定了重要基础。该文主要综述了ABA-binding protein/H subunit of Mgchelatase (ABAR/CHLH)、G protein-coupled receptor 2 (GCR2)、GPCR-type G protein 1/2 (GTG1/2)和pyrabactin resistant/PYR-like/regulatory component of ABA (PYR/PYL/RCAR)被报道为ABA受体的研究历程, 重点介绍了以ABAR/CHLH PYR/PYL/RCAR为受体的ABA信号转导通路模型的构建, 旨在为ABA受体及其信号转导通路的相关研究提供参考。     

植物激素脱落酸受体的研究进展

脱落酸（abscisic acid,ABA）广泛参与植物生长发育的调控和对多种环境胁迫的适应性反应。有关ABA受体的研究已经在检测受体位置、纯化ABA特异性的结合蛋白和克隆ABA受体基因方面做出了许多重要的工作。最近相继发现一种RNA结合蛋白FCA和一种编码Mg离子螯合酶（Mg-chelatase）H亚基的CHLH作为两种不同的ABA受体分别调控植物的开花时间和介导种子萌发、幼苗生长及叶片的气孔运动。本文从实验策略的角度重点分析总结了研究脱落酸受体相对有效的途径与方法,同时就有关的研究结果给予了评论和展望。     

脱落酸衍生物及其类似物研究进展

脱落酸是一种广泛存在于植物体内的植物激素,它与植物离层形成、诱导休眠、抑制发芽、促进器官衰老和脱落及增强抗逆性等密切相关。本文就其衍生物及类似物的研究做一概要综述,并对脱落酸的衍生化及结构改造与生物活性关系做了综合评价,从目前的情况来看,对8'或9'位甲基的衍生化是相对比较成功的,其中出现了一些活性较高的化合物,这也是近年来ABA衍生化研究的热点。     

脱落酸衍生物及其类似物研究进展

脱落酸是一种广泛存在于植物体内的植物激素,它与植物离层形成、诱导休眠、抑制发芽、促进器官衰老和脱落及增强抗逆性等密切相关.本文就其衍生物及类似物的研究做一概要综述,并对脱落酸的衍生化及结构改造与生物活性关系做了综合评价,从目前的情况来看,对8'或9'位甲基的衍生化是相对比较成功的,其中出现了一些活性较高的化合物,这也是近年来ABA衍生化研究的热点.     

植物激素脱落酸受体的研究进展

脱落酸(abscisic acid, ABA)广泛参与植物生长发育的调控和对多种环境胁迫的适应性反应。有关ABA受体的研究已经在检测受体位置、纯化ABA特异性的结合蛋白和克隆ABA受体基因方面做出了许多重要的工作。最近相继发现一种RNA结合蛋白FCA和一种编码Mg离子螯合酶（Mg-chelatase）H亚基的CHLH作为两种不同的ABA受体分别调控植物的开花时间和介导种子萌发、幼苗生长及叶片的气孔运动。本文从实验策略的角度重点分析总结了研究脱落酸受体相对有效的途径与方法, 同时就有关的研究结果给予了评论和展望。     

Studies of the Inhibition of Stomatal Opening by Naphth-1-ylacetic Acid and Abscisic Acid

Evidence is presented which confirms the inhibitory action ofthe synthetic auxin, NAA, on stomatal opening. In contrast tothe natural auxin IAA, NAA exerts effects which, in some respects,resemble those of ABA. The mode of action of NAA on the guardcells is, however, thought to be different from that of ABA.When NAA and ABA are applied together, their combined actionresults in a greater reduction in stomatal aperture than wouldbe predicted from their separate effects. Key words: NAA, ABA, IAA Stomata, Commelina     

Abscisic Acid Action on Basipetal Auxin Transport

Several experiments have been performed to analyse the ABA effects on the basipetal transport of IAA-2-¹⁴C, using sections of epicotyls prepared from etiolated Lens seedlings. The sections were incubated in an ABA solution or ABA was applied in the donor blocks containing IAA. For each type of assay, the uptake (analyses of the donor blocks) and the movement of IAA-C¹⁴ (analyses of the receiver blocks) were inhibited by ABA. The distribution of continuous decrease of the radioactivity, along the sections' axis, showed a ¹⁴C level from the apical towards the basal segments. ABA caused a decrease in the ¹⁴C concentration for the total sections, but a relative increase for the basal segment. When ABA was applied simultaneously with IAA in the donor blocks, the transport velocity of IAA, through the sections, was not changed significantly, while an ABA pretreatment caused a significant decrease.     

Abscisic Acid ELISA: Organic Acid Interference

Consideration must be exercised in determination of buffers and solutions used when carrying out enzyme-linked immunosorbent assays (ELISAs). A commercial monoclonal antibody kit for abscisic acid (Idetek, Inc.) gives significant false-positives with tricarboxylic acid cycle intermediates. The organic acids or contaminants interfered with ELISA assays for ABA as indicated by deviations in the slopes of standard curves of ABA in the organic acids. The interference, in the case of α-ketoglutarate, was caused by a contaminant. Of the organic buffers tested—Tris, Tricine, and Hepes—only Hepes showed false-positive ABA. In addition, we present data indicating the presence of ABA in commercial mannitol and provide a simple procedure for removal of the ABA.     

The Selective Effect of Abscisic Acid on Ribonucleic Acid Components

As determined by methylated albumin kieselguhr (MAK) fractionation, GA₃ (gibberellic acid) significantly increased and ABA (abscisic acid) decreased RNA levels. In the case of ABA this effect was selective, the ribosomal RNA manifesting the typical decrease; while the sRNA peak was markedly increased. The pattern of labelled uridine incorporation into RNA resembles the MAK absorbancy profile and here as well, ABA although causing an overall decrease, increases labelling in the sRNA peak. The results are interpreted as a possible selective effect of ABA or alternatively as an accumulation in the sRNA peak of rRNA breakdown products. From in vitro experiments it was furthermore evident that ABA mediated RNA hydrolysis probably does not involve a direct activation of RNase by ABA. The in vivo effect would probably be devious.     

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.     

脱落酸与种子休眠

从植物生理学、信号转导和基因表达三个方面综述了种子休眠与脱落酸之间关系的研究进展.