Metabolism and physiology of abscisic acid
01 Jan 1988-Vol. 39, Iss: 1, pp 439-473
TL;DR: This paper presents a meta-analysis of biosynthesis in Fungi, focusing on the role of xanthoxin in the biosynthetic pathway and its role in the regulation in plants.
Abstract: INTRODUCTION 440 TECHNIQUES 440 Quantification of ABA . ...... . . ...... . 440 Separation of Sand R-Abscisic Acid 441 Stable Isotopes and Mass Spectrometry 442 Extraction and Quantification of Xanthoxin 442 METABOLISM 443 Biosynthesis in Fungi 443 Biosynthesis in Higher Plants 444 Catabolism . . . . . . . . . .. . .... . . . . . . . . . . . . . . .. . . ..... . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... ..... . . . . . . . 453 Compartmentation 454 EFFECTS OF ABSCISIC ACID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 Physiological Responses 456 Biochemical Responses..... . ...... . 461 CONCLUDING REMARKS 463
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01 Jan 1982
TL;DR: In this article, the Soil as a Plant Nutrient Medium is discussed and the importance of water relations in plant growth and crop production, and the role of water as a plant nutrient medium.
Abstract: 1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.
4,130 citations
TL;DR: The responses of plants to salt and water stress are described, the regulatory circuits which allow plants to cope with stress are presented, and how the present knowledge can be applied to obtain tolerant plants is discussed.
Abstract: Agricultural productivity worldwide is subject to increasing environmental constraints, particularly to drought and salinity due to their high magnitude of impact and wide distribution. Traditional breeding programs trying to improve abiotic stress tolerance have had some success, but are limited by the multigenic nature of the trait. Tolerant plants such as Craterostigma plantagenium, Mesembryanthemum crystallinum, Thellungiella halophila and other hardy plants could be valuable tools to dissect the extreme tolerance nature. In the last decade, Arabidopsis thaliana, a genetic model plant, has been extensively used for unravelling the molecular basis of stress tolerance. Arabidopsis also proved to be extremely important for assessing functions for individual stress-associated genes due to the availability of knock-out mutants and its amenability for genetic transformation. In this review, the responses of plants to salt and water stress are described, the regulatory circuits which allow plants to cope wit...
2,351 citations
TL;DR: Identification of ABA metabolic genes has revealed that multiple metabolic steps are differentially regulated to fine-tune the ABA level at both transcriptional and post-transcriptional levels.
Abstract: The level of abscisic acid (ABAabscisic acid) in any particular tissue in a plant is determined by the rate of biosynthesis and catabolism of the hormone. Therefore, identifying all the genes involved in the metabolism is essential for a complete understanding of how this hormone directs plant growth and development. To date, almost all the biosynthetic genes have been identified through the isolation of auxotrophic mutants. On the other hand, among several ABA catabolic pathways, current genomic approaches revealed that Arabidopsis CYP707A genes encode ABA 8′-hydroxylases, which catalyze the first committed step in the predominant ABA catabolic pathway. Identification of ABA metabolic genes has revealed that multiple metabolic steps are differentially regulated to fine-tune the ABA level at both transcriptional and post-transcriptional levels. Furthermore, recent ongoing studies have given new insights into the regulation and site of ABA metabolism in relation to its physiological roles.
1,890 citations
Cites background from "Metabolism and physiology of abscis..."
...The hydroxylation at C-8′ position is commonly thought to be the predominant ABA catabolic pathway (20, 128)....
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...On the other hand, ABA 8′-hydroxylase is most likely the major regulatory enzyme in many physiological processes, as described below (20, 62, 93, 128)....
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...The 7′-hydroxy ABA is found in a variety of plant species as the minor catabolite (116, 128),...
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...In accordance, PA and DPA are the most widespread and abundant ABA catabolites (20, 128)....
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...Feeding experiments show that similar but distinct intermediates are identified among fungal genera (81, 128)....
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01 Jun 1998
TL;DR: Substantial evidence points to the importance of reversible protein phosphorylation and modifications of cytosolic calcium levels and pH as intermediates in ABA signal transduction.
Abstract: The plant hormone abscisic acid (ABA) plays a major role in seed maturation and germination, as well as in adaptation to abiotic environmental stresses. ABA promotes stomatal closure by rapidly altering ion fluxes in guard cells. Other ABA actions involve modifications of gene expression, and the analysis of ABA-responsive promoters has revealed a diversity of potential cis-acting regulatory elements. The nature of the ABA receptor(s) remains unknown. In contrast, combined biophysical, genetic, and molecular approaches have led to considerable progress in the characterization of more downstream signaling elements. In particular, substantial evidence points to the importance of reversible protein phosphorylation and modifications of cytosolic calcium levels and pH as intermediates in ABA signal transduction. Exciting advances are being made in reassembling individual components into minimal ABA signaling cascades at the single-cell level.
1,212 citations
Cites background from "Metabolism and physiology of abscis..."
...During vegetative growth, endogenous ABA levels increase upon conditions of water stress, and ABA is an essential mediator in triggering the plant responses to these adverse environmental stimuli (166)....
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...The characterization of these mutants, together with physicochemical studies, has enabled the pathway of ABA biosynthesis to be elucidated in higher plants (134, 135, 146, 166)....
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...These responses are rapid and are thus thought to be operationally distinct from long-term ABA responses that require RNA and protein synthesis (166)....
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TL;DR: Progress in identification of early stomatal signaling components are reviewed, including ABA receptors and CO(2)-binding response proteins, as well as systems approaches that advance the understanding of guard cell-signaling mechanisms.
Abstract: Stomatal pores are formed by pairs of specialized epidermal guard cells and serve as major gateways for both CO(2) influx into plants from the atmosphere and transpirational water loss of plants. Because they regulate stomatal pore apertures via integration of both endogenous hormonal stimuli and environmental signals, guard cells have been highly developed as a model system to dissect the dynamics and mechanisms of plant-cell signaling. The stress hormone ABA and elevated levels of CO(2) activate complex signaling pathways in guard cells that are mediated by kinases/phosphatases, secondary messengers, and ion channel regulation. Recent research in guard cells has led to a new hypothesis for how plants achieve specificity in intracellular calcium signaling: CO(2) and ABA enhance (prime) the calcium sensitivity of downstream calcium-signaling mechanisms. Recent progress in identification of early stomatal signaling components are reviewed here, including ABA receptors and CO(2)-binding response proteins, as well as systems approaches that advance our understanding of guard cell-signaling mechanisms.
1,169 citations
Cites background from "Metabolism and physiology of abscis..."
...Considering the wide range of roles of ABA in abiotic stress and developmental responses (161, 215), elucidating ABA metabolism is an important step in understanding the functions of ABA....
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...Three important questions on regulation of ABA metabolism arise: How is ABA synthesized and degraded? Where is ABA synthesized? and How is ABA metabolism activated? The enzymatic biosynthesis pathway of the sesquiterpenoid, abscisic acid, from C40 carotenoids has been well characterized biochemically and genetically (127, 215)....
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References
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TL;DR: Mutant lines of Arabidopsis thaliana (L.) Heynh, which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits than the wild type, and it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.
Abstract: Mutant lines of Arabidopsis thaliana (L.) Heynh., which are characterized by symptoms of withering and the absence of seed dormancy, showed much lower levels of endogenous abscisic acid (ABA) in developing seeds and fruits (siliquae) than the wild type. Reciprocal crosses of wild type and ABA-deficient mutants showed a dual origin of ABA in developing seeds. The genotype of the mother plant regulated a sharp rise in ABA content half-way seed development (maternal ABA). The genotype of the embryo and endosperm was responsible for a second ABA fraction (embryonic ABA), which reached much lower levels, but persisted for some time after the maximum in maternal ABA. The onset of dormancy correlated well with the presence of the embryonic ABA fraction and not with the maternal ABA. Dormancy developed in both the absence and presence of maternal ABA in the seeds. In this respect maternal ABA resembled exogenously applied ABA which did not induce dormancy in ABA-deficient seeds. However, both maternal and applied ABA stimulated the formation of a mucilage layer around the testa, which could be observed during imbibition of the mature seeds. In the mature state, ABA-deficient seeds germinated in the siliquae on the plant, but only when the atmosphere surrounding the plant was kept at high relative humidity. In younger stages germination in siliquae occurred after isolation from the plants and incubation on wet filter paper. Therefore, it seems that limited access to water is the primary trigger for the developmental arrest in these seeds.
569 citations
TL;DR: This chapter discusses the localization and regulation of ABA, the mode of action of A.lJA, and the role of stomatal complexes and A.spoTf in this synthesis.
Abstract: INTRODUCTION 454 TECHNIQUES ....... 454 Quantitation of ABA ... 454 Synthesis of Tritiated ABA 456 BIOCHEMISTRY 456 ABA Biosynthesis .... 456 ABA Metabolism 457 Regulation 0/ Enzyme Synthesis 460 PHYSIOLOGY 462 Water Stress 462 The stimulus fOT Ttlising ABA levels ..... ........ ........ .... ..... ..•.. .... 462 Localization and regulation of ABA. synthesis •••••••••••••••••••. ......... .... .... ........ .... 463 Stomatal complexes and A.lJA. ...... ......... ....... .... ..... ........ .... 466 Mode of action 467 A.lJA. levels and stomatal aperture ........ ....... ....... ......... ..... 469 Drought mistance ..... 470 Root Geotropism 470 Seed Development and Germination 472 Seed development 472 Seed gennil/Qtion 473 Dormancy 474 Induction of dormancy 474 Maintenance of dormancy 475 Correlative Inhibition 0/ Buds 475 Ion Movement 477 ABA tran.spoTf 478 CONCLUDING REMARKS 479
425 citations
TL;DR: Results are consistent with the hypothesis that in maturing rapeseeds, low water content rather than ABA prevents germination during the later stages of development.
Abstract: Development of Brassica napus L. cv Tower embryos of different ages cultured in vitro with and without abscisic acid (ABA) was compared with normal development in situ to investigate the role of ABA in embryo maturation. Endogenous ABA levels were measured by radioimmunoassay, and sensitivity to ABA was assayed in terms of its ability to suppress precocious germination and stimulate accumulation of storage protein and storage protein mRNA. During development in situ, the levels of endogenous ABA and 12S storage protein mRNA both reach their peaks just before the embryos begin to desiccate. The ABA levels during this phase of development also correlate with the time required in culture before germination is evident. Following these peaks, increasing concentrations of exogenous ABA are required to both suppress germination and continue storage protein accumulation in vitro. Thus, both endogenous ABA and ABA sensitivity decline during maturation. The concentrations of exogenous ABA required to suppress germination at these later stages result in abnormally high levels of endogenous ABA and appear to be toxic. These results are consistent with the hypothesis that in maturing rapeseeds, low water content rather than ABA prevents germination during the later stages of development.
307 citations
TL;DR: In this article, high affinity guard cell-specific ABA-binding proteins were found in the plasmalemma of the stomata of leaves with high density, and all characteristics examined, they bear the properties of ABA receptors.
Abstract: Stomata have a key role in the regulation of gas exchange and water economy in higher plants1,2. During water stress, they close in response to abscisic acid (ABA), a hormonal stimulus thought to be released or produced de novo in the mesophyll of leaves3,4, and probably in the guard cells of the stomata themselves5. By a mechanism still unknown, ABA affects the ionic balance of guard cells, resulting in a loss of K+, their major osmotically active constituent1,6. The structural requirements for a compound to be physiologically active in this system are stringent7 and suggest a highly specific interaction of the hormone with its primary target site(s). Apart from two preliminary studies8,9, ABA binding has not been investigated in plant material. Using guard cell protoplasts10,11, we have now obtained evidence for the occurrence of high-affinity guard cell-specific ABA-binding proteins which are located at the plasmalemma of these cells with high density. In all characteristics examined, they bear the properties of ABA receptors.
235 citations
TL;DR: Measurements of endogenous abscisic acid (ABA) levels by radioimmunoassay indicated that the osmotic effects on germination and gene expression were not mediated by elevated embryonic ABA, consistent with the hypothesis that ABA acts by inhibiting water uptake, which mechanically prevents germinating and affects gene expression in some unknown manner.
Abstract: The development of Brassica napus L. cv Tower embryos of different ages cultured in vitro with and without high osmoticum (0.48 and 0.69 molar sorbitol) was compared with normal development in situ to investigate the role of a drying environment in embryo maturation. Sensitivity to osmoticum was assayed in terms of its ability to mimic normal development, i.e. to both suppress germination and maintain 12 S storage protein (cruciferin) synthesis at levels comparable to those seen in the developing seed. The osmotic conditions used block germination of predesiccation stage embryos but were not sufficient to prevent desiccation stage embryos from taking up water and germinating. At all stages tested, the osmotically treated embryos had approximately normal levels of cruciferin mRNA. Measurements of endogenous abscisic acid (ABA) levels by radioimmunoassay indicated that the osmotic effects on germination and gene expression were not mediated by elevated embryonic ABA. Comparison of the kinetics of osmotic and ABA effects on gene expression showed that the osmotic effect is more rapid. These results are consistent with the hypothesis that ABA acts by inhibiting water uptake, which mechanically prevents germination and affects gene expression in some unknown manner.
205 citations