Rethinking Auxin Biosynthesis and Metabolism

Normanly, Jennifer; Slovin, Janet P.; Cohen, Jerry D.

doi:10.1104/pp.107.2.323

Cited by 199 publications

(111 citation statements)

References 30 publications

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“…IAN generally has been assumed to be a product of indole-3-acetaldoxime metabolism in IAA biosynthesis (e.g. Normanly et al, 1995;Bartel, 1997;Normanly and Bartel, 1999;Hull et al, 2000). However, the nit1-1 mutation that renders Arabidopsis seedlings insensitive to the IAA effects of exogenously applied IAN (Normanly et al, 1997) is unable to mitigate the auxin phenotype of rnt1-1 in double mutants (Bak et al, 2001).…”

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confidence: 99%

The Involvement of Two P450 Enzymes, CYP83B1 and CYP83A1, in Auxin Homeostasis and Glucosinolate Biosynthesis

Bak¹,

2001

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The first committed step in the biosynthesis of indole glucosinolates is the conversion of indole-3-acetaldoxime into an indole-3-S-alkyl-thiohydroximate. The initial step in this conversion is catalyzed by CYP83B1 in Arabidopsis (S. Bak, F.E. Tax, K.A. Feldmann, D.A. Galbraith, R. Feyereisen [2001] Plant Cell 13: 101-111). The knockout mutant of the CYP83B1 gene (rnt1-1) shows a strong auxin excess phenotype and are allelic to sur-2. CYP83A1 is the closest relative to CYP83B1 and shares 63% amino acid sequence identity. Although expression of CYP83A1 under control of its endogenous promoter in the rnt1-1 background does not prevent the auxin excess and indole glucosinolate deficit phenotype caused by the lack of the CYP83B1 gene, ectopic overexpression of CYP83A1 using a 35S promoter rescues the rnt1-1 phenotype. CYP83A1 and CYP83B1 heterologously expressed in yeast (Saccharomyces cerevisiae) cells show marked differences in their substrate specificity. Both enzymes convert indole-3-acetaldoxime to a thiohydroximate adduct in the presence of NADPH and a nucleophilic thiol donor. However, indole-3-acetaldoxime has a 50-fold higher affinity toward CYP83B1 than toward CYP83A1. Both enzymes also metabolize the phenylalanine-and tyrosine-derived aldoximes. Enzyme kinetic comparisons of CYP83A1 and CYP83B1 show that indole-3-acetaldoxime is the physiological substrate for CYP83B1 but not for CYP83A1. Instead, CYP83A1 catalyzes the initial conversion of aldoximes to thiohydroximates in the synthesis of glucosinolates not derived from tryptophan. The two closely related CYP83 subfamily members therefore are not redundant. The presence of putative auxin responsive cis-acting elements in the CYP83B1 promoter but not in the CYP83A1 promoter supports the suggestion that CYP83B1 has evolved to selectively metabolize a tryptophan-derived aldoxime intermediate shared with the pathway of auxin biosynthesis in Arabidopsis.

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The Involvement of Two P450 Enzymes, CYP83B1 and CYP83A1, in Auxin Homeostasis and Glucosinolate Biosynthesis

Bak¹,

2001

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“…It was proposed that the elevated IAA content in clubrootinfected tissue could be derived from indole glucosinolates (Butcher et al, 1974). To date, three different pathways for the synthesis of IAA in the Brassicaceae have been proposed (Normanly et al, 1995) : (1) via a non-tryptophan pathway, (2) via tryptophan, IAOX and IAN, and (3) via the indole glucosinolates. Pathways (1) and (2) are most likely to predominate in healthy tissue, whereas after pathogen invasion, indole glucosinolates can be degraded by myrosinase and further by nitrilase to IAA (Rausch et al, 1983).…”

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The host range of Plasmodiophora brassicae and its relationship to endogenous glucosinolate content

et al. 1999

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The host range of the soilborne obligate biotroph, Plasmodiophora brassicae was investigated. Evidence is presented that infection by P. brassicae might occur in non-Brassica species, leading to the potential formation of resting spores. Structures resembling P. brassicae were found in the root cortex of Tropaeolum majus, Carica papaya, Reseda alba and Beta vulgaris as demonstrated by scanning electron microscopy. Inoculation of Brassica rapa roots with spores extracted from either T. majus or B. vulgaris roots which had been previously inoculated with P. brassicae led to development of clubroot in the roots of B. rapa. It was also shown that the development of the symptom might be correlated with glucosinolate content, although other host factors are implicated in the B. vulgaris interaction with P. brassicae. In the glucosinolate-containing non-Brassicas, T. majus and C. papaya, the concentrations of benzylglucosinolate increased markedly in roots inoculated with P. brassicae, compared with the controls. There were also increases in concentrations of benzylglucosinolate in leaves of T. majus after P. brassicae infection. However, in R. alba roots, the total glucosinolate content decreased after inoculation with P. brassicae compared with the controls. High root concentrations of 2-OH-2-phenylethylglucosinolate (glucobarbarin) compared with low root indole glucosinolates in this species might limit P. brassicae infection and development. The importance of our investigations in relation to cultivation of non-Brassica species on fields infested with P. brassicae is discussed.

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“…In higher plants, the tryptophan (Trp) biosynthetic pathway provides an amino acid for protein synthesis, as well as precursors for secondary metabolites such as the phytohormoneindole-3-acetic acid and phytoalexins (Normanly et al, 1995). Trp decarboxylase has been studied ex tensively in plants and has shown to catalyse the first committed step in the production of indole alkaloids.…”

Section: Introductionmentioning

confidence: 99%

Changes in tryptophan production level in maize callus through modification of (ASA2) gene for enhancing defense mechanism

Abdel-Rahman¹,

Mohamed²,

Mousa³

2017

Egypt. J. Exp. Biol. (Bot.)

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Rethinking Auxin Biosynthesis and Metabolism

Cited by 199 publications

References 30 publications

The Involvement of Two P450 Enzymes, CYP83B1 and CYP83A1, in Auxin Homeostasis and Glucosinolate Biosynthesis

The Involvement of Two P450 Enzymes, CYP83B1 and CYP83A1, in Auxin Homeostasis and Glucosinolate Biosynthesis

The host range of Plasmodiophora brassicae and its relationship to endogenous glucosinolate content

Changes in tryptophan production level in maize callus through modification of (ASA2) gene for enhancing defense mechanism

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