Buckwheat Seedling Flavonoids Do not Undergo Rapid Turnover

Margna, Udo; Vainjärv, T.

doi:10.1016/s0015-3796(81)80007-8

Cited by 10 publications

(5 citation statements)

References 11 publications

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“…These data are corroborated by a field study on the alpine fern Cryptogramma crispa, which indicated that UV‐B screening pigments are synthesized within 12 h of exposure to sunlight, relative to plants under UV‐B absorbing screens (Veit et al ., 1996). However, laboratory studies on excised hypocotyls of crop plants indicate that flavonoids do not undergo rapid decomposition (Margna & Vainjärv, 1981) and glasshouse experiments using fluorescent UV lamps indicate that concentrations of flavonoid glycosides and aglycones in Betula pendula tissues may also take several days to respond to UV‐B radiation (Lavola et al ., 2000).…”

Section: Discussionmentioning

confidence: 99%

Response of two Antarctic bryophytes to stratospheric ozone depletion

Newsham

Hodgson

Murray

et al. 2002

Global Change Biology

123

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We report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (Fv/Fm) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata. We found a strong relationship between O3 column depth and the ratio of UV‐B to PAR irradiance (FUV‐B/FPAR) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV‐B radiation received at ground level. Regression analyses indicated that FUV‐B/FPAR and daily dose of unweighted UV‐B were best predictors for concentrations of total carotenoids and UV‐B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3‐dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ‐carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion. No direct associations between Fv/Fm and O3‐dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV‐B screening pigments conferred protection from elevated FUV‐B/FPAR on Fv/Fm in both species and that carotenoids conferred protection on Fv/Fm in Sanionia. Our data suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of two Antarctic bryophytes, but that Fv/Fm is unaffected, at least in part because of rapid synthesis of protective pigments.

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Section: Discussionmentioning

confidence: 99%

Response of two Antarctic bryophytes to stratospheric ozone depletion

Newsham

Hodgson

Murray

et al. 2002

Global Change Biology

123

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“…Two vitexin-derived 0-rhamnosides and one isovitexin 0-arabinoside are formed and show a slow turnover during the experimental period of ten days, thus indicating that the Cglycosides are not necessarily metabolic end products [26,27]. However, MARGNA and VAJNJARV [28] have demonstrated that amongst the maj or flavonoids of buckwheat seedlings (Fagopyrum esculentum, Fabaceae), rutin and the C-glycosyl flavonoids do not undergo appreciable turnover during a seven-day period.…”

Section: Biosynthesis Of C-glycosyl Flavonoidsmentioning

confidence: 97%

Chemistry, Occurrence and Biosynthesis ofC-Glycosyl Compounds in Plants

Franz

Grün

1983

Planta Med

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compounds with glucuronic acid have been found in mammals, which are probably analogous to C-glycosylated compounds in plants. C-Glucuronides of drugs in man [10] and other mammals [11, 12] represent a novel type of drug metabolite. As regards the biosynthetic pathway which leads to the formation of the carbon-carbon bond in C-glycosides, very little is known. In some cases it is thought that the attachment of the sugar moiety takes place during an early stage of the aglycone formation but definite proof is still missing and cannot be generalized for all groups of the C-glycosides. The aim of this article is to present a short review of the principal structural features and occurrence of the different classes of C-glycosides and further, to discuss the few biosynthetic findings of the C-glycosyl attachment which have been published so far. C-Glycosyl Flavonoids Chemistry of C-glycosyl Flavonoids As it has been pointed out, this group of C-glycosides has been the subject of a still increasing number of reports, which mainly deal with the occurrence and structural investigation of these compounds. Since they have been the subject of several review articles [3, 6, 7, 13, 14] only the main features are given here. At the present over one hundred C-glycosyl flavonoids have been shown to exist in the plant kingdom. The model compound and one of the first to be isolated was vitexin (8-C-3-D-glucopyranosylapigenm) (Fig. 2), the structure of which was established

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“…Cinnamic acid was, however, effectively converted into p‐ coumarate after the membranes were gently homogenized, presumably disrupting the interaction between PAL and C4H. In whole buckwheat seedlings, feeding experiments with labeled phenylalanine showed that only 20–25% of the label amppears in secondary metabolites, indicating that in intact cells even phenylalanine does not enter the pathway from a general metabolite pool (Margna and Vainjarv 1981).…”

Section: Evidence For the Channeling Of Intermediates In Phenylpropanmentioning

confidence: 99%

“…Together with the observation that the flavan‐3,4‐diol precursor does not accumulate to detectable levels, this finding was taken to suggest the existence of metabolite compartmentation or channeling in proanthocyanidin biosynthesis (Stafford 1981). The feeding experiments of Margna and Vainjarv (1981), using buckwheat seedlings, also demonstrated unequal utilization of common precursors in the synthesis of various flavonoid endproducts, suggesting that these metabolites are produced by the channeling of intermediates through different enzyme complexes. Similarly, precursor feeding experiments with alfalfa seedlings, treated with a fungal elicitor, have provided evidence for channeling in the isoflavonoid pathway (reviewed in Dixon et al 1998).…”

Section: Evidence For the Channeling Of Intermediates In Phenylpropanmentioning

confidence: 99%

Evidence for enzyme complexes in the phenylpropanoid and flavonoid pathways

Winkel-Shirley

1999

Physiologia Plantarum

259

150

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A growing body of evidence indicates that phenylpropanoid and flavonoid metabolism is catalyzed, not by free‐floating ‘soluble’ enzymes, but via one or more membrane‐associated multienzyme complexes. This type of macromolecular organization has important implications for the overall efficiency, specificity, and regulation of these pathways. Classical biochemical studies of phenylpropanoid and flavonoid metabolism have laid a solid foundation for this model, providing evidence of the channeling of intermediates between enzyme active sites and co‐localization of enzymes in cell membranes. This work is now being extended using transgenic plants to determine how the partitioning of metabolites within these pathways is controlled, as well as applying sensitive methods to define specific interactions among the individual enzymes. Information from these studies promises to provide new insights into the structuring of biosynthetic pathways within cells, which should lead to more effective means for engineering the production of plant metabolites with nutritional and agronomic importance.

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Buckwheat Seedling Flavonoids Do not Undergo Rapid Turnover

Cited by 10 publications

References 11 publications

Response of two Antarctic bryophytes to stratospheric ozone depletion

Response of two Antarctic bryophytes to stratospheric ozone depletion

Chemistry, Occurrence and Biosynthesis ofC-Glycosyl Compounds in Plants

Evidence for enzyme complexes in the phenylpropanoid and flavonoid pathways

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