Metabolism of indole-3-acetaldoxime in plants

Rajagopal, R.; Larsen, Poul

doi:10.1007/bf00394605

Cited by 45 publications

(28 citation statements)

References 16 publications

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“…It should be noted, however, that a direct conversion pathway from IAOx to IAA or indole-3 ethanol has been postulated before (31), and, based on our data, the existence of such a pathway cannot be precluded. Interestingly, this pathway uses IAAld and not IAN as an intermediate from which IAA or indole-3 ethanol is formed by oxidation or reduction.…”

Section: Discussionmentioning

confidence: 45%

“…IAAld is the precursor of IAA in the Trp-indole-3-pyruvic acid-IAAld-IAA pathway, which may indicate a deregulation of this pathway in the sur2 mutant. However, IAAld has been also postulated to be an intermediate in the Trp-IAOx-IAN-IAA pathway (30,31). Labeling experiments showed that only minute amounts of label were transferred from IAAld to IAA, indicating that no real up-regulation of the Trp-indole-3-pyruvic acid-IAAld-IAA pathway occurred.…”

Section: Discussionmentioning

confidence: 99%

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TheSUR2gene ofArabidopsis thalianaencodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis

Barlier

Kowalczyk

Marchant

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

277

226

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Genetic screens have been performed to identify mutants with altered auxin homeostasis in Arabidopsis. A tagged allele of the auxin-overproducing mutant sur2 was identified within a transposon mutagenized population. The SUR2 gene was cloned and shown to encode the CYP83B1 protein, which belongs to the large family of the P450-dependent monooxygenases. SUR2 expression is up-regulated in sur1 mutants and induced by exogenous auxin in the wild type. Analysis of indole-3-acetic acid (IAA) synthesis and metabolism in sur2 plants indicates that the mutation causes a conditional increase in the pool size of IAA through up-regulation of IAA synthesis.

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Section: Discussionmentioning

confidence: 45%

Section: Discussionmentioning

confidence: 99%

TheSUR2gene ofArabidopsis thalianaencodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis

Barlier

Kowalczyk

Marchant

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

277

226

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“…At present, it is not clear how IAOx is converted to IAA. IAN generally has been considered as the primary intermediate between IAOx and IAA, although IAAld has also been proposed (Rajagopal and Larsen 1972). IAN measurements in CYP79B2ox lines and the cyp79B2 and cyp79B3 single and double mutants are consistent with IAN being a direct IAA intermediate.…”

Section: A Framework For Trp-dependent Iaa Biosynthesismentioning

confidence: 91%

Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3

Zhao¹,

Hull²,

Gupta³

et al. 2002

Genes Dev.

582

644

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The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the two Arabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and show growth defects consistent with partial auxin deficiency. Together with previous work on YUCCA, a flavin monooxygenase also implicated in IAOx production, and nitrilases that convert indole-3-acetonitrile to auxin, this work provides a framework for further dissecting auxin biosynthetic pathways and their regulation.

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“…Labeling studies have shown that indole-3-acetaldoxime can be converted to IAA with indole-3-acetaldehyde as an intermediate in higher plants (Rajapogal and Larsen, 1972). Accordingly, it has been shown that in the IAA overproducer sur1, the aldehyde oxidase activity is increased (Seo et al, 1998).…”

Section: The Role Of Ian In Iaa Biosynthesismentioning

confidence: 99%

CYP83B1, a Cytochrome P450 at the Metabolic Branch Point in Auxin and Indole Glucosinolate Biosynthesis in Arabidopsis

et al. 2001

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Auxins are growth regulators involved in virtually all aspects of plant development. However, little is known about how plants synthesize these essential compounds. We propose that the level of indole-3-acetic acid is regulated by the flux of indole-3-acetaldoxime through a cytochrome P450, CYP83B1, to the glucosinolate pathway. A T-DNA insertion in the CYP83B1 gene leads to plants with a phenotype that suggests severe auxin overproduction, whereas CYP83B1 overexpression leads to loss of apical dominance typical of auxin deficit. CYP83B1 N-hydroxylates indole-3-acetaldoxime to the corresponding aci -nitro compound, 1-aci -nitro-2-indolyl-ethane, with a K m of 3 M and a turnover number of 53 min Ϫ 1 . The aci -nitro compound formed reacts non-enzymatically with thiol compounds to produce an N -alkyl-thiohydroximate adduct, the committed precursor of glucosinolates. Thus, indole-3-acetaldoxime is the metabolic branch point between the primary auxin indole-3-acetic acid and indole glucosinolate biosynthesis in Arabidopsis. INTRODUCTIONApical dominance, cell expansion, vascular differentiation, lateral root and root hair formation, phototropism, and root gravitropism are among the many processes in plants controlled by auxins (Davies, 1995). The level of auxin is regulated by both de novo biosynthesis and reversible and irreversible conjugation to sugars, amino acids, and peptides as well as by degradation. Although the chemical structure of the primary auxin, indole-3-acetic acid (IAA), has been known since the 1930s (Wildman, 1997), not much is known about how plants actually synthesize this essential compound. Plants appear to be capable of synthesizing IAA by both tryptophan-dependent and tryptophan-independent pathways. Classical incorporation studies with radiolabeled compounds have not unambiguously identified the precursors or elucidated the biosynthetic pathway for IAA. (For a recent review of IAA metabolism, see Normanly and Bartel [1999].)Although a number of mutants in IAA metabolic pathways and perception have been described, the genes involved and their biochemical function and physiological relevance have not all been elucidated (reviewed in Bartel, 1997;Normanly and Bartel, 1999). For example, both the rty/sur1/hls3/alf1 (Boerjan et al., 1995;Celenza et al., 1995;King et al., 1995;Lehman et al., 1996) and sur2 mutants are known to accumulate increased levels of free auxin. Identification of the gene products affected and elucidation of the biochemical roles of these proteins should increase our limited knowledge of IAA biosynthesis and regulation.A link between indole glucosinolates and auxin has often been suggested in the literature. Glucosinolates are sulfurcontaining bioactive natural products derived from amino acids and sequestered in vacuoles of cruciferous plants (Halkier, 1999). It has recently been shown that the cytochromes CYP79B2 and CYP79B3 of Arabidopsis metabolize tryptophan to indole-3-acetaldoxime. This metabolite is often suggested to be the precursor of indole-3-acetonitrile (IAN...

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Metabolism of indole-3-acetaldoxime in plants

Cited by 45 publications

References 16 publications

TheSUR2gene ofArabidopsis thalianaencodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis

TheSUR2gene ofArabidopsis thalianaencodes the cytochrome P450 CYP83B1, a modulator of auxin homeostasis

Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3

CYP83B1, a Cytochrome P450 at the Metabolic Branch Point in Auxin and Indole Glucosinolate Biosynthesis in Arabidopsis

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