The biosynthesis of glucosinolates

Halkier, Barbara Ann; Du, Liangcheng

doi:10.1016/s1360-1385(97)90026-1

Cited by 234 publications

(147 citation statements)

References 24 publications

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“…Several alternatives have been proposed, including the existence of both tryptophan-dependent and tryptophanindependent pathways in A. thaliana (44)(45)(46)(47). Furthermore, although indolic glucosinolates were not among the major substances identified under the present conditions, they are known to be derived from tryptophan and believed to act as phytoanticipins in pathogen defense (26,27,48,49). Thus they may constitute a relatively low-abundance or otherwise undetected group of compounds.…”

Section: Discussionmentioning

confidence: 91%

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Hagemeier¹

2001

Proceedings of the National Academy of Sciences

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The chemical structures and accumulation kinetics of several major soluble as well as wall-bound, alkali-hydrolyzable compounds induced upon infection of Arabidopsis thaliana leaves with Pseudomonas syringae pathovar tomato were established. All identified accumulating products were structurally related to tryptophan. Most prominent among the soluble substances were tryptophan, ␤-D-glucopyranosyl indole-3-carboxylic acid, 6-hydroxyindole-3-carboxylic acid 6-O-␤-D-glucopyranoside, and the indolic phytoalexin camalexin. The single major accumulating wall component detectable under these conditions was indole-3-carboxylic acid. All of these compounds increased more rapidly, and camalexin as well as indole-3-carboxylic acid reached much higher levels, in the incompatible than in the compatible P. syringae͞A. thaliana interaction. The only three prominent phenylpropanoid derivatives present in the soluble extract behaved differently. Two kaempferol glycosides remained largely unaffected, and sinapoyl malate decreased strongly upon bacterial infection with a time course inversely correlated with that of the accumulating tryptophan-related products. The accumulation patterns of both soluble and wallbound compounds, as well as the disease resistance phenotypes, were essentially the same for infected wild-type and tt4 (no kaempferol glycosides) or fah1 (no sinapoyl malate) mutant plants. Largely different product combinations accumulated in wounded or senescing A. thaliana leaves. It seems unlikely that any one of the infection-induced compounds identified so far has a decisive role in the resistance response to P. syringae.

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Section: Discussionmentioning

confidence: 91%

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Hagemeier¹

2001

Proceedings of the National Academy of Sciences

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Section: Glucosinolate Biosynthesismentioning

confidence: 99%

“…The S-alkyl-thiohydroximate formed by CYP83B1 catalysis can be cleaved by a C-S lyase to generate thiohydroximates. It is well established that thiohydroximates are glucosylated by a soluble UDPG:thiohydroximate glucosyltransferase to form desulfoglucosinolates that are subsequently sulfated by a soluble 3Ј-phosphoadenosine 5Ј-phosphosulphate:desulphoglucosinolate sulphotransferase (PAPS transferase) (reviewed in Halkier and Du, 1997).Arabidopsis contains at least 23 different glucosinolates derived from tryptophan and from chain-elongated homologs of phenylalanine and methionine (Hogge et al, 1988). In Arabidopsis, at least six related members of the CYP79 family (http://ag.arizona.edu/p450) have been identified.…”

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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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“…The first step in glucosinolate biosynthesis is the oxidation of the amino group to an oxime moiety by amino acid-specific cytochrome P450 monooxygenases (Du et al, 1995;Wittstock and Halkier, 2000). After a thiohydroximate intermediate is formed, sequential transfer of glucose and sulfate residues creates the basic glucosinolate skeleton (Halkier and Du, 1997). The initially formed glucosinolate can undergo a variety of subsequent transformations that modify the side chain.…”

Section: Introductionmentioning

confidence: 99%

Gene Duplication in the Diversification of Secondary Metabolism: Tandem 2-Oxoglutarate–Dependent Dioxygenases Control Glucosinolate Biosynthesis in Arabidopsis

et al. 2001

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Secondary metabolites are a diverse set of plant compounds believed to have numerous functions in plant-environment interactions. The large chemical diversity of secondary metabolites undoubtedly arises from an equally diverse set of enzymes responsible for their biosynthesis. However, little is known about the evolution of enzymes involved in secondary metabolism. We are studying the biosynthesis of glucosinolates, a large group of secondary metabolites, in Arabidopsis to investigate the evolution of enzymes involved in secondary metabolism. Arabidopsis contains natural variations in the presence of methylsulfinylalkyl, alkenyl, and hydroxyalkyl glucosinolates. In this article, we report the identification of genes encoding two 2-oxoglutarate-dependent dioxygenases that are responsible for this variation. These genes, AOP2 and AOP3 , which map to the same position on chromosome IV, result from an apparent gene duplication and control the conversion of methylsulfinylalkyl glucosinolate to either the alkenyl or the hydroxyalkyl form. By heterologous expression in Escherichia and the correlation of gene expression patterns to the glucosinolate phenotype, we show that AOP2 catalyzes the conversion of methylsulfinylalkyl glucosinolates to alkenyl glucosinolates. Conversely, AOP3 directs the formation of hydroxyalkyl glucosinolates from methylsulfinylalkyl glucosinolates. No ecotype coexpressed both genes. Furthermore, the absence of functional AOP2 and AOP3 leads to the accumulation of the precursor methylsulfinylalkyl glucosinolates. A third member of this gene family, AOP1 , is present in at least two forms and found in all ecotypes examined. However, its catalytic role is still uncertain.

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The biosynthesis of glucosinolates

Cited by 234 publications

References 24 publications

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

Accumulation of soluble and wall-bound indolic metabolites in Arabidopsis thaliana leaves infected with virulent or avirulent Pseudomonas syringae pathovar tomato strains

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

Gene Duplication in the Diversification of Secondary Metabolism: Tandem 2-Oxoglutarate–Dependent Dioxygenases Control Glucosinolate Biosynthesis in Arabidopsis

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