Gene Clusters for Secondary Metabolic Pathways: An Emerging Theme in Plant Biology

Osbourn, Anne

doi:10.1104/pp.110.161315

Cited by 96 publications

(81 citation statements)

References 41 publications

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“…The colocalization of genes encoding diterpene synthases and CYP726A proteins led us to speculate that these genes may form part of a gene cluster (Osbourn, 2010). To investigate this further, we performed spatial gene expression analysis of the genes present within the putative cluster and determined the ability of the CYP726A to modify casbene and neocembrene.…”

Section: Resultsmentioning

confidence: 99%

Production of Bioactive Diterpenoids in the Euphorbiaceae Depends on Evolutionarily Conserved Gene Clusters

et al. 2014

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The Euphorbiaceae produce a diverse range of diterpenoids, many of which have pharmacological activities. These diterpenoids include ingenol mebutate, which is licensed for the treatment of a precancerous skin condition (actinic keratosis), and phorbol derivatives such as resiniferatoxin and prostratin, which are undergoing investigation for the treatment of severe pain and HIV, respectively. Despite the interest in these diterpenoids, their biosynthesis is poorly understood at present, with the only characterized step being the conversion of geranylgeranyl pyrophosphate into casbene. Here, we report a physical cluster of diterpenoid biosynthetic genes from castor (Ricinus communis), including casbene synthases and cytochrome P450s from the CYP726A subfamily. CYP726A14, CYP726A17, and CYP726A18 were able to catalyze 5-oxidation of casbene, a conserved oxidation step in the biosynthesis of this family of medicinally important diterpenoids. CYP726A16 catalyzed 7,8-epoxidation of 5-keto-casbene and CYP726A15 catalyzed 5-oxidation of neocembrene. Evidence of similar gene clustering was also found in two other Euphorbiaceae, including Euphorbia peplus, the source organism of ingenol mebutate. These results demonstrate conservation of gene clusters at the higher taxonomic level of the plant family and that this phenomenon could prove useful in further elucidating diterpenoid biosynthetic pathways.

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Section: Resultsmentioning

confidence: 99%

Production of Bioactive Diterpenoids in the Euphorbiaceae Depends on Evolutionarily Conserved Gene Clusters

et al. 2014

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“…chromosome 4 (Frey et al, 2009). In general, such an organization of functionally related genes in operon-like gene clusters in plants is considered to facilitate the coregulation of gene expression (Jonczyk et al, 2008;Osbourn, 2010), which, however, would imply less regulatory flexibility at the single gene level. While DIMBOA-Glc is mainly produced in young seedlings 4 to 6 d after germination and declines thereafter, the production of HDMBOAGlc and HDM 2 BOA-Glc also occurs in older tissues (Cambier et al, 2000;Köhler et al, 2015).…”

Section: Natural Variation In Bx7 Bx13 and Bx14 Expressionmentioning

confidence: 99%

Biosynthesis of 8-O-methylated benzoxazinoid defense compounds in maize

et al. 2016

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Benzoxazinoids are important defense compounds in grasses. Here, we investigated the biosynthesis and biological roles of the 8-O-methylated benzoxazinoids, DIM 2 BOA-Glc and HDM 2 BOA-Glc. Using quantitative trait locus mapping and heterologous expression, we identified a 2-oxoglutarate-dependent dioxygenase (BX13) that catalyzes the conversion of DIMBOA-Glc into a new benzoxazinoid intermediate (TRIMBOA-Glc) by an uncommon reaction involving a hydroxylation and a likely ortho-rearrangement of a methoxy group. TRIMBOA-Glc is then converted to DIM 2 BOA-Glc by a previously described O-methyltransferase BX7. Furthermore, we identified an O-methyltransferase (BX14) that converts DIM 2 BOA-Glc to HDM 2 BOA-Glc. The role of these enzymes in vivo was demonstrated by characterizing recombinant inbred lines, including Oh43, which has a point mutation in the start codon of Bx13 and lacks both DIM 2 BOA-Glc and HDM 2 BOA-Glc, and Il14H, which has an inactive Bx14 allele and lacks HDM 2 BOA-Glc in leaves. Experiments with near-isogenic maize lines derived from crosses between B73 and Oh43 revealed that the absence of DIM 2 BOA-Glc and HDM 2 BOA-Glc does not alter the constitutive accumulation or deglucosylation of other benzoxazinoids. The growth of various chewing herbivores was not significantly affected by the absence of BX13-dependent metabolites, while aphid performance increased, suggesting that DIM 2 BOA-Glc and/or HDM 2 BOA-Glc provide specific protection against phloem feeding insects.

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“…It is worth mentioning that, despite the lack of typical transit peptides, the plant-mPLoc tool (Chou, 2005;Shen and Chou, 2006;Chou and Shen, 2007, 2010 predicts that the wheat and barley DMHs localize to the chloroplast or the nucleus, but not the ER. Surely, further studies are required in order to fully characterize the DMH enzyme activity and its subcellular localization in both barley and wheat.…”

Section: Activity Of Dmh As a Hydrolase/carboxylesterase And The Linkmentioning

confidence: 99%

A Metabolic Gene Cluster in the Wheat W1 and the Barley Cer-cqu Loci Determines β-Diketone Biosynthesis and Glaucousness

et al. 2016

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The glaucous appearance of wheat (Triticum aestivum) and barley (Hordeum vulgare) plants, that is the light bluish-gray look of flag leaf, stem, and spike surfaces, results from deposition of cuticular b-diketone wax on their surfaces; this phenotype is associated with high yield, especially under drought conditions. Despite extensive genetic and biochemical characterization, the molecular genetic basis underlying the biosynthesis of b-diketones remains unclear. Here, we discovered that the wheat W1 locus contains a metabolic gene cluster mediating b-diketone biosynthesis. The cluster comprises genes encoding proteins of several families including type-III polyketide synthases, hydrolases, and cytochrome P450s related to known fatty acid hydroxylases. The cluster region was identified in both genetic and physical maps of glaucous and glossy tetraploid wheat, demonstrating entirely different haplotypes in these accessions. Complementary evidence obtained through gene silencing in planta and heterologous expression in bacteria supports a model for a b-diketone biosynthesis pathway involving members of these three protein families. Mutations in homologous genes were identified in the barley eceriferum mutants defective in b-diketone biosynthesis, demonstrating a gene cluster also in the b-diketone biosynthesis Cer-cqu locus in barley. Hence, our findings open new opportunities to breed major cereal crops for surface features that impact yield and stress response.

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Gene Clusters for Secondary Metabolic Pathways: An Emerging Theme in Plant Biology

Cited by 96 publications

References 41 publications

Production of Bioactive Diterpenoids in the Euphorbiaceae Depends on Evolutionarily Conserved Gene Clusters

Production of Bioactive Diterpenoids in the Euphorbiaceae Depends on Evolutionarily Conserved Gene Clusters

Biosynthesis of 8-O-methylated benzoxazinoid defense compounds in maize

A Metabolic Gene Cluster in the Wheat W1 and the Barley Cer-cqu Loci Determines β-Diketone Biosynthesis and Glaucousness

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