The isolation and identification of the prosthetic group released from a bound form of abscisic acid

A bound form of abscisic acid, herein called adduct, has been isolated from peas and barley and has been shown to release methyl abscisate upon mild acid hydrolysis. Mass spectrometry of the methyl abscisate released by ²H₂SO₄ in ²H₂O showed that the remainder of adduct was linked as an enolate of the ketone of the moiety that releases methyl abscisate. Some evidence is adduced to suggest that adduct is a metabolic precursor of abscisic acid. The implications of the distribution of adduct between roots and shoots for the plant's response to stress is discussed.     

诺丽青果化学成分研究

干燥诺丽青果粉末95％乙醇提取物的正丁醇萃取部分经硅胶、Sephadex LH-20和LiChmprep RP-18等材料分离,波谱学方法鉴定了8个化合物,分别为乌苏酸（1）、6,7-二羟基香豆素（2）、胡萝卜甙（3）、车叶革甙（4）、Borreriagenin（5）、去乙酰车叶草甙（6）、O-β-D-glucopyranoside scopolln（7）、车叶草酸（8）。其中化合物7为首次从该种中分到。     

Enzymatic Resolution of (±)-Epoxy-β-cyclogeraniol,a Synthetic Precursor for Abscisic Acid Analogs

Lipase-catalyzed optical resolution of (±)-epoxy-β-cyclogeraniol (1), a key synthetic intermediate for epoxy-β-ionylideneacetic acid, was achieved in high enantiomeric purity. Transesterification with vinyl acetate by using lipase P (Nagase) made enriched (-)-1, while hydrolysis of the corresponding acetate by using lipase P (Amano) afforded (+)-1 with a high E value (E=1600).     

Incorporation of α-ionylidene ethanol and α-ionylidene acetic acid into abscisic acid by Cercospora rosicola

²H-Labelled α-ionylidene ethanol and α-ionylidene acetic acid are converted in high yield to 1′-deoxy-abscisic acid (1′-deoxy-ABA) and absc     

A novel abscisic acid metabolite from seeds of Robinia pseudacacia

Abscisic acid and its novel metabolise, which was a conjugated form of hydroxyabscisic acid (Metabolite C), were isolated from seeds of Robinia pseudacacia L. The structure of the conjugate was shown to be (+)-3-methyl-5 - [1(S),6(R) - 2,6 - dimethyl - 1 - hydroxy - 6 - (3 - hydroxy - 3 - methyl - 4 - carboxybutanoyloxymethyl) - 4 - oxo-cyclohex-2-enyl]-2-Z-4-E-pentadienoic acid and tentatively named β-hydroxy-β-methylglutarylhydroxyabscisic acid.     

Studies on the Chemical Constituents of Duzhong (The Bark of Eucommia ulmoides Oliv.)

Four constituents were isolated from the bark of Eucommia ulmoide; Oliv. Based on the physico-chemical constants, spectral analysis and properties of derivatives, they were identified as: liriodendrin (1), geniposidic acid (2), (+)-pinoresinol di-O-β-D-glucopyranoside (3), and daucosterol.     

始于质体/叶绿体的ABA信号通路

该文全面评述了植物激素脱落酸（ABA）受体的研究进展概况,重点介绍细胞内ABA受体ABAR/镁螯合酶H亚基CHLH对ABA信号感知和向下游转导的研究进展,总结了ABAR介导的、起始于质体/叶绿体的ABA信号通路。ABAR是一个跨越叶绿体被膜的蛋白质,其N-端和C-端暴露在细胞质中;ABAR在细胞质一侧的C-端部分与一组WRKY转录因子（WRKY18、WRKY40、WRKY60）相互作用。WRKY18、WRKY40和WRKY60是一组转录抑制因子。它们互相协作,抑制下游重要的ABA信号调节子基因（如ABI4、ABI5、ABF4和MYB2等）的表达,从而负调节ABA信号通路。WRKY40是其中的核心调节子,WRKY18协助加强WRKY40对ABA信号的负调节。ABAR与ABA信号分子结合后,可以刺激WRKY40从细胞核转移至细胞质,促进ABAR与WRKY40的相互作用;进而激发一种未知因子（或信号系统）,阻遏WRKY40的表达,从而解除WRKY40对ABA响应基因转录的抑制,最终实现ABA的生理效应。这些发现描述了一个从信号原初识别到下游基因表达的新的ABA信号通路。论文最后对未来该领域的研究方向进行了讨论。     

Stress-dependent redistribution of abscisic acid (ABA) in Hordeum vulgare L leaves: the role of epidermal ABA metabolism, tonoplastic transport and the cuticle

When ¹⁴C-labelled abscisic acid ([¹⁴C]ABA) was supplied to isolated protoplasts of the barley leaf at pH 6, initial rates of metabolism were about five times higher in epidermal cell protoplasts than in mesophyll cell protoplasts if equal cytosolic volumes were considered. In spite of the fact that epidermal cells make up only about 35% of the total water space in barley leaves, and despite the small cytosolic volume of these cells, in intact leaves all epidermal cells would thus metabolize half as much ABA per unit time as the mesophyll cells (0–27 and 0–51 mmol h^?1 m^?3 leaf water). Therefore, under these conditions epidermal cells seem to be a stronger sink than mesophyll cells for ABA that arrives via the transpiration stream. However, at an apoplastic pH of 7–25, which occurs in stressed leaves, the proportion of total metabolized ABA would be much smaller in epidermal than in mesophyll cells (0–029 and 0–204 mmolh^?l m^?3 leaf water). Our results indicate that under conditions of slightly alkaline apoplastic pH the epidermis may serve as the main source for fast stress-dependent ABA redistribution into the guard cell apoplast. This is partly the result of ABA transport across the epidermal tonoplast, which is dependent on the apoplastic pH and possibly on the cytosolic calcium concentration. The cuticle seems to be of no particular importance in stress-induced apoplastic ABA shifts and cannot be regarded as a significant sink for high ABA concentrations under stress.     

The biosynthesis of abscisic acid in Cercospora rosicola

1′-Deoxyabscisic acid (1′-deoxy-ABA) has been isolated from cultures of Cercospora rosicola which are actively synthesizing abscisic acid (ABA)     

K+ channel activity in plants: genes, regulations and functions

Potassium (K(+)) is the most abundant cation in the cytosol, and plant growth requires that large amounts of K(+) are transported from the soil to the growing organs. K(+) uptake and fluxes within the plant are mediated by several families of transporters and channels. Here, we describe the different families of K(+)-selective channels that have been identified in plants, the so-called Shaker, TPK and Kir-like channels, and what is known so far on their regulations and physiological functions in the plant.     

Enzymic Preparation of Benzyl β-D-Glucopyranoside

Benzyl β-D-glucopyranoside was prepared by an enzyme-catalysed direct reaction between D-glucose, or better cellobiose, and benzyl alcohol in the presence of a minimum amount of water. The enzyme β-glucosidase was used in the immobilized form (adsorbed onto macroporous polyethylene terephthalate or covalently bound on polyglycidyl methacrylate), enabling multiple application.     

A Novel Pathway for the Partial Oxidation of Propionyl-CoA to Pyruvate via Seven-carbon Tricarboxylic Acids in Yeasts

We examined the biosynthetic pathway of abscisic acid (ABA) after isopentenyl diphosphate in a fungus, Cercospora cruenta. All oxygen atoms at C-1, -1, -1′, and -4′ of ABA produced by this fungus were labeled with ¹⁸O from ¹⁸O₂. The fungus did not produce the 9Z-carotenoid possessing γ-ring that is likely a precursor for the carotenoid pathway, but produced new sesquiterpenoids, 2E,4E-γ-ionylideneethane and 2Z,4E-γ-ionylideneethane, along with 2E,4E,6E-allofarnesene. The fungus converted these sesquiterpenoids labeled with ¹³C to ABA, and the incorporation ratio of 2Z,4E-γ-ionylideneethane was higher than that of 2E,4E-γ-ionylideneethane. From these results, we concluded that C. cruenta biosynthesized ABA by the direct pathway via oxidation of ionylideneethane with molecular oxygen following cyclization of allofarnesene. This direct pathway via ionylideneethane in the fungus is consistent with that in Botrytis cinerea, except for the positions of double bonds in the rings of biosynthetic intermediates, suggesting that the pathway is common among ABA-producing fungi.     

Maize VP1 complements Arabidopsisabi3 and confers a novel ABA/auxin interaction in roots

The maize Vp1 gene and abi3 gene of Arabidopsis are believed to be orthologs based on similarities of the mutant phenotypes and amino acid sequence conservation. Here we show that expression of VP1 driven by the 35S promoter can partially complement abi3-6, a deletion mutant allele of abi3. The visible phenotype of seed produced from VP1 expression in the abi3 mutant background is nearly indistinguishable from wild type. VP1 fully restores abscisic acid (ABA) sensitivity of abi3 during seed germination and suppresses the early flowering phenotype of abi3. The temporal regulation of C1-beta-glucuronidase (GUS) and chlorophyll a/b binding protein (cab3)-GUS reporter genes in developing seeds of 35S-VP1 lines were similar to wild type. On the other hand, two qualitative differences are observed between the 35S-VP1 line and wild type. The levels of CRC and C1-GUS expression are markedly lower in the seeds of 35S-VP1 lines than in wild type suggesting incomplete complementation of gene activation functions. Similar to ectopic expression of ABI3 (Parcy et al., 1994), ectopic expression of VP1 in vegetative tissue enhances ABA inhibition of root growth. In addition, 35S-VP1 confers strong ABA inducible expression of the normally seed-specific cruciferin C (CRC) gene in leaves. In contrast, ectopic ABA induction of C1-GUS is restricted to a localized region of the root elongation zone. The ABA-dependent C1-GUS expression expanded to a broader area in the root tissues treated with exogenous application of auxin. Interestingly, auxin-induced lateral root formation is completely suppressed by ABA in 35S-VP1 plants but not in wild type. These results indicate VP1 mediates a novel interaction between ABA and auxin signaling that results in developmental arrest and altered patterns of gene expression.     

Molecular cloning in Arabidopsis thaliana of a new protein phosphatase 2C (PP2C) with homology to ABI1 and ABI2

We report the cloning of both the cDNA and the corresponding genomic sequence of a new PP2C from Arabidopsis thaliana, named AtP2C-HA (for homology to ABI1/ABI2). The AtP2C-HA cDNA contains an open reading frame of 1536 bp and encodes a putative protein of 511 amino acids with a predicted molecular mass of 55.7 kDa. The AtP2C-HA protein is composed of two domains, a C-terminal PP2C catalytic domain and a N-terminal extension of ca. 180 amino acid residues. The deduced amino acid sequence is 55% and 54% identical to ABI1 and ABI2, respectively. Comparison of the genomic structure of the ABI1, ABI2 and AtP2C-HA genes suggests that they belong to a multigene family. The expression of the AtP2C-HA gene is up-regulated by abscisic acid (ABA) treatment.     

Immunoenzyme method for differential assay of free and bound ABA

We performed the immunochemical study of two solid-phase competitive ELISA systems differing in their specificity toward free and bound ABA. A possible application of these systems for the quantification of natural ABA forms without their preliminary separation and purification in a single sample of plant material was demonstrated.     

A simplified purification method for the analysis of abscisic acid

A fast and convenient method is given for the purification of abscisic acid (ABA) in plant extracts. Using a dual pH elution system on Sep-Pak C18 reverse phase prepacked cartridges, abscisic acid appears in the third eluent (32% methanol pH 8.0). The cartridges can be regenerated for multiple reuse.     

Plant apocarotenoids: from retrograde signaling to interspecific communication

Carotenoids are isoprenoid compounds synthesized by all photosynthetic and some non-photosynthetic organisms. They are essential for photosynthesis and contribute to many other aspects of a plant's life. The oxidative breakdown of carotenoids gives rise to the formation of a diverse family of essential metabolites called apocarotenoids. This metabolic process either takes place spontaneously through reactive oxygen species or is catalyzed by enzymes generally belonging to the CAROTENOID CLEAVAGE DIOXYGENASE family. Apocarotenoids include the phytohormones abscisic acid and strigolactones (SLs), signaling molecules and growth regulators. Abscisic acid and SLs are vital in regulating plant growth, development and stress response. SLs are also an essential component in plants’ rhizospheric communication with symbionts and parasites. Other apocarotenoid small molecules, such as blumenols, mycorradicins, zaxinone, anchorene, β-cyclocitral, β-cyclogeranic acid, β-ionone and loliolide, are involved in plant growth and development, and/or contribute to different processes, including arbuscular mycorrhiza symbiosis, abiotic stress response, plant–plant and plant–herbivore interactions and plastid retrograde signaling. There are also indications for the presence of structurally unidentified linear cis-carotene-derived apocarotenoids, which are presumed to modulate plastid biogenesis and leaf morphology, among other developmental processes. Here, we provide an overview on the biology of old, recently discovered and supposed plant apocarotenoid signaling molecules, describing their biosynthesis, developmental and physiological functions, and role as a messenger in plant communication.