Abscisic Acid Metabolism by a Cell-free Preparation from <i>Echinocystis lobata</i> Liquid Endoserum

Gillard, Douglas F.; Walton, Daniel C.

doi:10.1104/pp.58.6.790

Cited by 105 publications

(45 citation statements)

References 24 publications

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“…is not shifted. These data support the conclusion (2) that ABA hydroxylating enzyme is an oxygenase and are consistent with Gillett's rule (3) that biological hydroxylation of a methyl group involves the direct participation of molecular oxygen. ABA levels in stressed leaves of X. strumarium increased, and the vacuum-flush treatment had no effect on accumulation of ABA (Table II).…”

Section: Resultssupporting

confidence: 79%

Incorporation of Oxygen into Abscisic Acid and Phaseic Acid from Molecular Oxygen

Creelman¹,

Zeevaart²

1984

Plant Physiol.

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Abscisic acid accumulates in detached, wilted leaves of Xanthium strumarium. When these leaves are subsequently rehydrated, phaseic acid, a catabolite of abscisic acid, accumulates. Analysis by ps chromatography-mass spectrometry of phaseic acid isolated from stressed and subsequently rehydrated leaves placed in an atmosphere containing 20% I802 and 80% N2 indicates that one atom of "0 is incorporated in the 6'-hydroxymethyl group of phaseic acid. This suggests that the enzyme that converts abscisic acid to phaseic acid is an oxygenase.Analysis by gas chromatography-mass spectrometry of abscisic acid isolated from stressed leaves kept in an atmosphere containing "02indicates that one atom of "IO is present in the carboxyl group of abscisic acid. Thus, when abscisic acid accumulates in water-stressed leaves, only one of the four oxygens present in the abscisic acid molecule is derived from molecular oxygen. This suggests that either (a) the oxygen present in the 1'-, 4'-, and one of the two oxygens at the 1-position of abscisic acid arise from water, or (b) there exists a stored precursor with oxygen atoms already present in the 1'-and 4'-positions of abscisic acid which is converted to abscisic acid under conditions of water stress.Little is known about the biosynthetic pathway ofABA, except that as a sesquiterpenoid, ABA is ultimately derived from MVA.2 When radioactive MVA was applied to higher plant tissues, the percentage of incorporation into ABA was always very low, and no intermediates have ever been isolated. Some controversy exists as to whether ABA is synthesized from a C-15 precursor, presumably farnesyl pyrophosphate (the direct pathway), or results from the degradation of a C-40 precursor (the indirect pathway), such as the xanthophyll violaxanthin (6). It is known that the stereochemistry of protons in ABA derived from MVA is identical to that found in carotenoids and it should be noted that the terminal ring structure of certain xanthophylls is similar to ABA (6).Oxygen incorporation into carotenes to form xanthophylls is a late step in carotenoid biosynthesis occurring after ring formation. The oxygen atoms in the hydroxyl groups of lutein and the epoxide groups of antheraxanthin and violaxanthin are derived from molecular oxygen (12,13 bons of the ABA molecule should be a late step in the pathway, the oxygens being derived from molecular oxygen.With respect to ABA catabolism, Gillard and Walton (2) have shown with a crude enzyme preparation from Echinocystis lobata that hydroxylation at the 6'-methyl group to give PA via the unstable intermediate 6'-hydroxymethyl-ABA, is inhibited by CO and anaerobic conditions. They concluded that the enzyme involved is very similar to Cyt P-450 monooxygenases found in animals, but it did not meet all the criteria necessary for calling ABA hydroxylating enzyme a Cyt P450 monooxygenase. These criteria are: (a) inhibition of the reaction in the presence of CO, (b) presence in the reduced enzyme preparation ofa CO-binding pigment with a maximum A at 450 nm...

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Section: Resultssupporting

confidence: 79%

Incorporation of Oxygen into Abscisic Acid and Phaseic Acid from Molecular Oxygen

Creelman¹,

Zeevaart²

1984

Plant Physiol.

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“…It was clear, however, that some aleurone activity occurred. The probable explanation for this lesser aleurone activity is that abscisic acid was metabolised to a glucosidic form which lacked anti-gibberellic acid activity (14,26). Such metabolism of abscisic acid by barley aleurone layers has been reported by WALTON'S group (8).…”

Section: Distal Decapitation Experimentsmentioning

confidence: 86%

On the relative role of the scutellum and aleurone in the production of hydrolases during germination of barley

Gibbons

1981

Carlsberg Res. Commun.

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The relative roles of the scutellum and the aleurone layer in the production and mediation of both germination-specific a-amylase and cell wall breakdown hydrolases has been examined in vivo following treatment of barley seeds with the plant hormones gibberellic acid and abscisic acid. To facilitate entry of these exogenous hormones, a technique is presented where multiple incisions b~nicks~0 are made in the outer layers of the seed prior to germination. Treatment of seeds with gibberellic acid and abscisic acid effected major changes on the pattern of hydrolase transport. The nature of the changes were such that it is concluded that the scutellum alone is capable of producing and mediating up to 50To of germination specific hydrolases in a commercial European malting barley, germinating at the conventional European malting temperature of 15 ~

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“…The major ABA catabolic pathway in higher plants involves oxidation of ABA by ABA 8#-hydroxylase to form 8#-hydroxy ABA. In the subsequent step, 8#-hydroxy ABA is spontaneously isomerized to phaseic acid (PA), which is further reduced to dihydrophaseic acid (DPA) by an unknown reductase (Gillard and Walton, 1976;Krochko et al, 1998;Cutler and Krochko, 1999). The genes encoding ABA 8#-hydroxylase were identified to be members of the subfamily of CYP707A (Kushiro et al, 2004;Saito et al, 2004).…”

mentioning

confidence: 99%

High Humidity Induces Abscisic Acid 8′-Hydroxylase in Stomata and Vasculature to Regulate Local and Systemic Abscisic Acid Responses in Arabidopsis

Okamoto

Tanaka²,

Abrams³

et al. 2008

Plant Physiol.

228

190

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Levels of endogenous abscisic acid (ABA) are changed dynamically in response to environmental conditions. The ABA 8#-hydroxylase is a key enzyme in ABA catabolism and is encoded by CYP707A genes. In this study, we examined physiological roles of Arabidopsis (Arabidopsis thaliana) CYP707As in the plant's response to changes in humidity. The cyp707a1 and cyp707a3 mutants displayed lower stomatal conductance under turgid conditions (relative humidity 60%) than the wild type. When wild-type plants were transferred to high-humidity conditions (relative humidity 90%), CYP707A1 and CYP707A3 transcript levels increased, followed by the reduction of ABA levels. The cyp707a3 mutant exhibited high ABA levels even after transferring to high-humidity conditions, whereas, under similar conditions, the cyp707a1 mutant exhibited low ABA levels comparable to the wild type. Analysis of spatial expression patterns by using transgenic plants harboring a promoter:: b-glucuronidase gene indicated that high-humidity-induced expression of CYP707A1 and CYP707A3 occurred primarily in guard cells and vascular tissues, respectively. Furthermore, stomatal closure of the cyp707a1 mutant, but not cyp707a3 mutant, was ABA hypersensitive when epidermal peel was treated with exogenous ABA, suggesting that CYP707A1 is essential for ABA catabolism inside the guard cells. These results implicate that CYP707A3 reduces the amount of mobile ABA in vascular tissues in response to high humidity, whereas CYP707A1 inactivates local ABA pools inside the guard cells. Taken together, ABA catabolism in both vascular tissues and guard cells participates in the systemic ABA action that controls stomatal movement in response to high humidity.

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Abscisic Acid Metabolism by a Cell-free Preparation from Echinocystis lobata Liquid Endoserum

Cited by 105 publications

References 24 publications

Incorporation of Oxygen into Abscisic Acid and Phaseic Acid from Molecular Oxygen

Incorporation of Oxygen into Abscisic Acid and Phaseic Acid from Molecular Oxygen

On the relative role of the scutellum and aleurone in the production of hydrolases during germination of barley

High Humidity Induces Abscisic Acid 8′-Hydroxylase in Stomata and Vasculature to Regulate Local and Systemic Abscisic Acid Responses in Arabidopsis

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