- Functional characterization of wheat ent-kaurene(-like) synthases indicates continuing evolution of labdane-related diterpenoid metabolism in the cereals
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Wheat (Triticum aestivum) and rice (Oryza sativa) are two of the most agriculturally important cereal crop plants. Rice is known to produce numerous diterpenoid natural products that serve as phytoalexins and/or allelochemicals. Specifically, these are labdane-related diterpenoids, derived from a characteristic labdadienyl/copalyl diphosphate (CPP), whose biosynthetic relationship to gibberellin biosynthesis is evident from the relevant expanded and functionally diverse family of ent-kaurene synthase-like (KSL) genes found in rice the (OsKSLs). Herein reported is the biochemical characterization of a similarly expansive family of KSL from wheat (the TaKSLs). In particular, beyond ent-kaurene synthases (KS), wheat also contains several biochemically diversified KSLs. These react either with the ent-CPP intermediate common to gibberellin biosynthesis or with the normal stereoisomer of CPP that also is found in wheat (as demonstrated by the accompanying paper describing the wheat CPP synthases). Comparison with a barley (Hordeum vulgare) KS indicates conservation of monocot KS, with early and continued expansion and functional diversification of KSLs in at least the small grain cereals. In addition, some of the TaKSLs that utilize normal CPP also will react with syn-CPP, echoing previous findings with the OsKSL family, with such enzymatic promiscuity/elasticity providing insight into the continuing evolution of diterpenoid metabolism in the cereal crop plant family, as well as more generally, which is discussed here.
- Zhou, Ke,Xu, Meimei,Tiernan, Mollie,Xie, Qian,Peters, Reuben J.,Toyomasu, Tomonobu,Sugawara, Chizu,Oku, Madoka,Usui, Masami,Mitsuhashi, Wataru,Chono, Makiko,Chandler, Peter M.
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p. 47 - 55,9
(2012/12/12)
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- Functional characterization of wheat ent-kaurene(-like) synthases indicates continuing evolution of labdane-related diterpenoid metabolism in the cereals
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Wheat (Triticum aestivum) and rice (Oryza sativa) are two of the most agriculturally important cereal crop plants. Rice is known to produce numerous diterpenoid natural products that serve as phytoalexins and/or allelochemicals. Specifically, these are labdane-related diterpenoids, derived from a characteristic labdadienyl/copalyl diphosphate (CPP), whose biosynthetic relationship to gibberellin biosynthesis is evident from the relevant expanded and functionally diverse family of ent-kaurene synthase-like (KSL) genes found in rice the (OsKSLs). Herein reported is the biochemical characterization of a similarly expansive family of KSL from wheat (the TaKSLs). In particular, beyond ent-kaurene synthases (KS), wheat also contains several biochemically diversified KSLs. These react either with the ent-CPP intermediate common to gibberellin biosynthesis or with the normal stereoisomer of CPP that also is found in wheat (as demonstrated by the accompanying paper describing the wheat CPP synthases). Comparison with a barley (Hordeum vulgare) KS indicates conservation of monocot KS, with early and continued expansion and functional diversification of KSLs in at least the small grain cereals. In addition, some of the TaKSLs that utilize normal CPP also will react with syn-CPP, echoing previous findings with the OsKSL family, with such enzymatic promiscuity/elasticity providing insight into the continuing evolution of diterpenoid metabolism in the cereal crop plant family, as well as more generally, which is discussed here.
- Zhou, Ke,Xu, Meimei,Tiernan, Mollie,Xie, Qian,Toyomasu, Tomonobu,Sugawara, Chizu,Oku, Madoka,Usui, Masami,Mitsuhashi, Wataru,Chono, Makiko,Chandler, Peter M.,Peters, Reuben J.
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- Synthesis of ent-Kaurene from a Naturally Occurring Precursor
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ent-Kaurene (1) has been synthesized from a naturally occurring precursor, ent-kaurane-17,19-diol (3a).Selective deoxygenation at C19 of the diol was achieved after the C17 hydroxyl was protected as the triphenylmethyl ether. ent-Kaurene was then prepared by way of an elimination sequence at C17.
- Hogg, Ronald W.,Knox, John R.
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p. 469 - 474
(2007/10/02)
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- Synthesis and Evaluation of Cyclobutylcarbinyl Derivatives as Potential Intermediates in Diterpene Biosynthesis
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A new mechanism for the enzyme-catalyzed bicyclization of copalyl pyrophosphate (1) to kaurene (2) and related bridged perhydrophenanthrene-type diterpenes is considered.The key steps in the mechanism are an exocyclic vinyl group ring closure of the pimar-15-en-8-yl carbocation to a D-norbeyerane-15-methyl intermediate (D) and a subsequent ring expansion (A -> D -> B) instead of the usual endocyclic pimarenyl -> beyeranyl cyclization (A -> B).Beyeran-16-one (7), prepared in six steps from isosteviol methyl ester (5b), was converted to 16-diazobeyeran-15-one (10) viathe 15,16-dione.Irradiation of the diazo ketone afforded an exo-endo mixture of D-norbeyerane-15-carboxylic acids or esters (11 and 12).The isomeric esters were separated by selective hydrolysis and reduced to the exo- and endo-cyclobutylcarbinols (13-OH and 14-OH).Acetolysis of the corresponding tosylates initiated a ring-expansion rearrangement to beyerene, kaurene, and isokaurene, as well as fragmentation to 7,15-, 8,15-, and 8(14),15-pimaradienes (Scheme III).However, the lack of incorporation of either 3H>-13-OPP or 3H>-14-OPP into kaurene upon incubation with a kaurene synthetase preparation from Marah macrocarpus ruled out the exo- and endo-cyclobutylcarbinyl pyrophosphates as free intermediates in the cyclization catalyzed by this enzyme.
- Coates, Robert M.,Kang, Han-Young
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p. 2065 - 2074
(2007/10/02)
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- BIOSYNTHESIS OF GIBBERELLIN A12-ALDEHYDE, GIBBERELLIN A12 AND THEIR KAURENOID PRECURSORS FROM MEVALONIC ACID IN A CELL-FREE SYSTEM FROM IMMATURE SEED OF PHASEOLUS COCCINEUS
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A cell-free system capable of gibberellin (GA) biosynthesis has been prepared from immature seed of Phaseolus coccineus.This system converted mevalonic acid (MVA) to ent-kaurene, ent-kaurenoic acid, ent-kauradienoic acid, ent-7α-hydroxykaurenoic acid, ent-6α,7α-dihydroxykaurenoic acid, GA12-aldehyde and GA12. ent-Kaurene was converted to ent-kaurenol, ent-kaurenal, ent-kaurenoic acid and ent-7α-hydroxykaurenoic acid.All identifications were by GC/MC.The pathway from MVA to GA12-aldehyde in this species thus appears to be the same as that found in cell-free preparations derived from immature seed of other species.Key Word Index-Phaseolus coccineus; Leguminosae; runner bean; seed development; biosynthesis; cell-free system; HPLC; GC/MC; gibberellin.
- Turnbull, Colin G. N.,Crozier, Alan,Schwenen, Ludger,Graebe, Jan E.
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