Anatomy of Sorgoleone‐Secreting Root Hairs of<i>Sorghum</i>Species

Czarnota, Mark A.; Paul, Rex N.; Weston, Leslie A.; Duke, Stephen O.

doi:10.1086/378661

Cited by 87 publications

(76 citation statements)

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“…Tissue-Specific Accumulation of the 5-[(Z,Z)-89,119,149-Pentadecatrienyl]Resorcinol Intermediate Given the evidence obtained from prior studies (e.g., Czarnota et al, 2001Czarnota et al, , 2003a, it is reasonable to speculate that the ARSs participating in the biosynthesis of sorgoleone are predominantly or exclusively expressed in root hairs and that the expected product, 5-pentadecatrienyl resorcinol, should also predominantly accumulate within this cell type. To explore this further, methanol extracts prepared from root hairs, root systems, developing panicles, stems, immature and fully expanded leaves, and shoot apices were analyzed by gas chromatography-mass spectrometry (GC-MS) for the presence of 5-[(Z,Z)-89,119,149-pentadecatrienyl]resorcinol.…”

Section: Resultsmentioning

confidence: 97%

“…The biosynthesis of sorgoleone is thought to occur exclusively in root hairs, which appear as cytoplasmically dense cells in sorghum, containing large osmiophilic globules presumably associated with sorgoleone rhizosecretion (Czarnota et al, 2001(Czarnota et al, , 2003a. Prior labeling studies have indicated a polyketide origin for the quinone ring of sorgoleone (Fate and Lynn, 1996;Dayan et al, 2003), thus lending support for the initial steps in the proposed biosynthetic pathway shown in Figure 1, in which 5-pentadecatrienyl resorcinol (5-[(Z,Z)-89,119,149-pentadecatrienyl]resorcinol) is produced by a polyketide synthase enzyme accepting a 16:3D 9,12,15 fatty acyl-CoA starter unit.…”

Section: Introductionmentioning

confidence: 99%

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Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone

et al. 2010

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Sorghum bicolor is considered to be an allelopathic crop species, producing phytotoxins such as the lipid benzoquinone sorgoleone, which likely accounts for many of the allelopathic properties of Sorghum spp. Current evidence suggests that sorgoleone biosynthesis occurs exclusively in root hair cells and involves the production of an alkylresorcinolic intermediate (5-[(Z,Z)-89,119,149-pentadecatrienyl]resorcinol) derived from an unusual 16:3D 9,12,15 fatty acyl-CoA starter unit. This led to the suggestion of the involvement of one or more alkylresorcinol synthases (ARSs), type III polyketide synthases (PKSs) that produce 5-alkylresorcinols using medium to long-chain fatty acyl-CoA starter units via iterative condensations with malonyl-CoA. In an effort to characterize the enzymes responsible for the biosynthesis of the pentadecyl resorcinol intermediate, a previously described expressed sequence tag database prepared from isolated S. bicolor (genotype BTx623) root hairs was first mined for all PKS-like sequences. Quantitative real-time RT-PCR analyses revealed that three of these sequences were preferentially expressed in root hairs, two of which (designated ARS1 and ARS2) were found to encode ARS enzymes capable of accepting a variety of fatty acyl-CoA starter units in recombinant enzyme studies. Furthermore, RNA interference experiments directed against ARS1 and ARS2 resulted in the generation of multiple independent transformant events exhibiting dramatically reduced sorgoleone levels. Thus, both ARS1 and ARS2 are likely to participate in the biosynthesis of sorgoleone in planta. The sequences of ARS1 and ARS2 were also used to identify several rice (Oryza sativa) genes encoding ARSs, which are likely involved in the production of defense-related alkylresorcinols.

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Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone

et al. 2010

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“…8,13 The cell-specific localization and prolific output of the sorgoleone biosynthetic pathway rendered the use of expressed sequence tag (EST) analysis the obvious method of choice in our efforts to isolate genes encoding sorgoleone biosynthetic enzymes. 14 Labeling studies performed by Fate & Lynn, 15 first demonstrated that biosynthesis proceeds through the action of an alkylresorcinol synthase (ARS), a novel type III polyketide synthase activity utilizing fatty acyl-CoA starter units (Fig.…”

Section: Use Of Functional Genomics To Explore Sorgoleone Biosynthesismentioning

confidence: 99%

Probing allelochemical biosynthesis in sorghum root hairs

Baerson

Rimando

Pan

2008

Plant Signaling & Behavior

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Allelopathic interaction between plants is thought to involve the release of phytotoxic allelochemicals by one species, thus inhibiting the growth of neighboring species in competition for limited resources. Sorgoleone represents one of the more potent allelochemicals characterized to date, and its prolific production in root hair cells of Sorghum spp. has made the investigation of its biosynthetic pathway ideally-suited for functional genomics investigations. Through the use of a recently-released EST data set generated from isolated Sorghum bicolor root hair cells, significant inroads have been made toward the identification of genes and the corresponding enzymes involved in the biosynthesis of this compound in root hairs. Here we provide additional information concerning our recent report on the identification of a 5-n-alk(en) ylresorcinol utilizing O-methyltransferase, as well as other key enzymes likely to participate in the biosynthesis of this important allelochemical.

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“…According to Rice (1984), the effects of sorghum allelochemicals are concentration-dependent and selective. Cheema (1988) reports at least nine water-soluble allelochemicals from mature sorghum plants that are phytotoxic to weeds, such as Phalaris minor Retz., Chenopodium album L., Rumex dentatus L. and Convolvulus arvensis L. However, the most studied metabolites exudated by the living roots of sorghum are a group of hydrophobic benzoquinones called sorgoleone -2-hydroxy-5-methoxy-3-[(Z, Z)-8', 11', 14'-pentadecatriene]-pbenzoquinone and its 1,4-hydroquinone (Czarnota et al, , 2003a. It was discovered in roots of S. bicolor by Netzly and Butler (1986) when these authors were investigating seed stimulants of Striga asiatica (L.) Ktze.…”

Section: Sorghum [Sorghum Bicolor (L) Moench and Sorghum Sudanense mentioning

confidence: 99%

Allelopathy, an alternative tool to improve cropping systems. A review

Albuquerque

Santos

Lima

et al. 2010

Agronomy Sust. Developm.

172

122

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-Known since ancient times, the phenomenon of allelopathy has recently received greater attention from researchers and farmers worldwide. Crop failures and low yields caused by the reseeding, overseeding, crop rotation and replanting of fruit trees in orchards are believed to be caused by allelopathic activity. Moreover, the expensive and environmentally impacting herbicides for weed control have motivated studies directed at developing cheaper, environmentally-friendly alternatives. Despite the difficulties in separating chemical interference from other mechanisms, more modern approaches have produced consistent and conclusive data on this topic. The release and dynamics of allelochemicals in the soil are discussed herein. Examples of allelopathic crops, the allelochemicals produced and their uses in cropping systems are also presented along with current research trends regarding allelopathy. allelopathy / chemical interference / agriculture / potential use

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Anatomy of Sorgoleone‐Secreting Root Hairs ofSorghumSpecies

Cited by 87 publications

References 40 publications

Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone

Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone

Probing allelochemical biosynthesis in sorghum root hairs

Allelopathy, an alternative tool to improve cropping systems. A review

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