Abscisic acid 670856 224842801 2008-07-10T17:42:40Z Epbr123 1395162 Reverted edits by [[Special:Contributions/92.0.159.23|92.0.159.23]] to last version by Epbr123 (using [[WP:HG|Huggle]]) {{expert}} {{Chembox new | Name = '''Abscisic acid''' | ImageFile = abscisic acid structure.png | ImageSize = 200px | ImageName = Abscisic acid | IUPACName = [''S''-(''Z,E'')]-5-(1-Hydroxy-2,6,6 -trimethyl-4-oxo-2-cyclohexen- 1-yl)-3-methyl-2,4-pentanedienoic acid<ref>[http://www.abscisic.com/abscisic-chemical-name.php Abscisic Acid Chemical Name]</ref> | Section1 = {{Chembox Identifiers | Abbreviations = ABA | CASNo = 21293-29-8 | SMILES = CC1=CC(CC(C)(C)[C@@](/C=C/C(C) =C\C(O)=O)1O)=O | InChI=1/C15H20O4/c1-10(7-<br />13(17)18)5-6-15(19)<br />11(2)8-12(16)9-14<br />(15,3)4/h5-8,19H,9H2,<br />1-4H3,(H,17,18)/b6-<br />5+,10-7-/t15-/m0/s1/<br />f/h17H }} | Section2 = {{Chembox Properties | Formula = C<sub>15</sub>H<sub>20</sub>O<sub>4</sub> | MolarMass = 264.32 g/mol | Density = | MeltingPt = 161&ndash;163 °C | BoilingPt = 120 °C (sublimes)}} }} '''Abscisic acid''' (ABA), also known as '''abscisin II''' and '''dormin''', is a [[plant hormone]]. It functions in many plant developmental processes, including bud [[dormancy]]. ==Function== ABA was originally believed that it was involved in [[abscission]] but researchers no longer believe this to be the case. ABA-mediated signalling also plays an important part in plant responses to environmental stress and plant pathogens.<ref name="Zhu">{{cite journal|author=Zhu JK.|year= 2002|title=Salt and drought stress signal transduction in plants|journal=Annu Rev Plant Biol.|volume=53|pages=247–273|pmid=12221975|doi=10.1146/annurev.arplant.53.091401.143329}}</ref><ref name="Seo and Koshiba">{{cite journal|author=Seo M, Koshiba T|year= 2002|title=Complex regulation of ABA biosynthesis in plants|journal=Trends Plant Sci.|volume=7|pages=41–48|pmid=11804826|doi=10.1016/S1360-1385(01)02187-2}}</ref> The plant genes for ABA biosynthesis and sequence of the pathway have been elucidated.<ref name="Nambara and Marion-Poll">{{cite journal|author=Nambara E, Marion-Poll A.|year= 2005|title=Abscisic acid biosynthesis and catabolism|journal=Annu Rev Plant Biol.|volume=56|pages=165–185|pmid=15862093|doi=10.1146/annurev.arplant.56.032604.144046}}</ref><ref name="Milborrow">{{cite journal|author=Milborrow BV|year= 2001|title=The pathway of biosynthesis of abscisic acid in vascular plants: a review of the present state of knowledge of ABA biosynthesis|journal=J Exp Bot.|volume=52|pages=1145–1164|pmid=11432933|doi=10.1093/jexbot/52.359.1145}}</ref> ABA is also produced by some plant pathogenic fungi via a biosynthetic route different from ABA biosynthesis in plants.<ref name="Siewers">{{cite journal|author=Siewers V, Smedsgaard J, Tudzynski P.|year= 2004|title=The P450 monooxygenase BcABA1 is essential for abscisic acid biosynthesis in Botrytis cinerea|journal=Appl Environ. Microbiol.|volume=70|pages=3868–3876|pmid=15240257|doi=10.1128/AEM.70.7.3868-3876.2004}}</ref> Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in [[Bud#Types of buds|terminal buds]]. {{Fact|date=September 2007}} This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season. ABA also inhibits the division of cells in the vascular [[cambium]], adjusting to cold conditions in the winter by suspending primary and secondary growth. Abscisic acid is also produced in the [[root]]s in response to decreased soil [[water potential]] and other situations in which the plant may be under stress. ABA then translocates to the leaves, where it rapidly alters the osmotic potential of stomatal guard cells, causing them to shrink and [[stomata]] to close. The ABA-induced stomatal closure reduces [[transpiration]] thus preventing further water loss from the leaves in times of low water availability. Several ABA [[mutant]] ''[[Arabidopsis thaliana]]'' plants have been identified – both those deficient in ABA production and those insensitive to its action. ABA-deficient plants show defects in [[seed]] dormancy, [[germination]], [[stomata]]l regulation and some mutants show stunted growth and brown/yellow leaves.<ref>[http://arabidopsis.info/ NASC - Arabidopsis Stock Centre]</ref> These mutants reflect the importance of ABA in seed germination and early embryo development. ==Biosynthesis== Abscisic acid (ABA) is an [[isoprenoid]] plant hormone, which is synthesized in the [[plastid]]al 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway; unlike the structurally related [[sesquiterpene]]s, which are formed from the [[mevalonic acid]]-derived precursor [[farnesyl diphosphate]] (FDP), the C<sub>15</sub> backbone of ABA is formed after cleavage of C<sub>40</sub> [[carotenoid]]s in MEP. [[Zeaxanthin]] is the first committed ABA precursor; a series of enzyme-catalyzed [[epoxidation]]s and [[isomerization]]s, and final cleavage of the C<sub>40</sub> [[carotenoid]] by a [[dioxygenation]] reaction yields the proximal ABA precursor, [[xanthoxin]], which is then further oxidized to ABA.<ref name="Nambara and Marion-Poll">. Abamine has been patented by the Japanese researchers Shigeo Yoshida and Tadao Asami, which are very reluctant to make this substance available in general, neither commercially nor for research purposes. <ref name="US patent 7098365"> {{ http://www.google.com.au/patents?id=BnN6AAAAEBAJ}}</ref> ==Location and timing of ABA biosynthesis== * Released during [[desiccation]] of the vegetative tissues and when roots encounter soil [[compaction]].<ref>DeJong-Hughes, J., et al. (2001) Soil Compaction: causes, effects and control. University of Minnesota extension service</ref> * Synthesized in green [[fruit]] and [[seed]]s at the beginning of the wintering period * Mobile within the [[leaf]] and can be rapidly translocated from the roots to the leaves by the transpiration stream in the [[xylem]]. * Produced in response to [[environmental stress]], such as heat stress, water stress, salt stress. * Synthesized in all plant parts, e.g. roots, flowers, leaves and [[Plant stem|stems]] ==Effects== * Induces [[stomata]]l closure, reducing transpiration to prevent water loss.<ref>Zhang, J., U. Schurr, and W.J. Davies, Control of Stomatal Behaviour by Abscisic Acid which Apparently Originates in the Roots. ''Journal of Experimental Botany'', 1987. '''38'''(7): p. 1174.</ref> * Inhibits [[fruit ripening]] * Responsible for seed dormancy by inhibiting cell growth &ndash; inhibits seed [[germination]] * Inhibits the uptake of [[Kinetin]] * Downregulates [[enzyme]]s needed for [[photosynthesis]].<ref>Plant, A.R., GENE EXPRESSION REGULATED BY ABSCISIC ACID AND ITS RELATION TO STRESS TOLERANCE. ''Annu. Rev. Plant Physiol. Plant Mol. Biol'', 1994. '''45''': p. 113-141.</ref> ==References== <references/> {{Plant hormones}} [[Category:plant hormones]] [[Category:carboxylic acids]] [[bn:অ্যাবসিসিক অ্যাসিড]] [[cs:Kyselina abscisová]] [[da:Abscisinsyre]] [[de:Abscisinsäure]] [[es:Ácido abscísico]] [[fr:Acide abscissique]] [[it:Acido abscissico]] [[he:חומצה אבציסית]] [[nl:Abscisinezuur]] [[ja:アブシジン酸]] [[pl:Kwas abscysynowy]] [[pt:Ácido abscísico]] [[fi:Abskissihappo]] [[tr:Absisik asit]] [[zh:離層酸]]