Different l-phenylalanine pools available for the biosynthesis of phenolics in buckwheat seedling tissues

Margna, Udo; Vainjärv, T.; Laanest, L.

doi:10.1016/0031-9422(89)80034-2

Cited by 18 publications

(11 citation statements)

References 19 publications

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“…The process is similar to that identified in bacteria and fungi, wherein prephenate is converted to phenylpyruvate by PD, and phenylpyruvate is converted to Phe by phenylalanine aminotransferase (Gilchrist & Kosuge 1980;Warpeha et al 2006). Given the very small pools of Phe in seeds and in developing seedlings, and the potential for large demands on this pool (Margna 1977;Margna et al 1989), especially in times of stress or anticipation of stress, it remains possible that it is the ability to synthesize Phe that is limiting to the production of phenylpropanoid pathway products, and therefore is limiting to the ability to screen or protect in a variety of ways from harmful UV-B.…”

Section: Introductionmentioning

confidence: 96%

“…Because of its two roles, as a precursor to both protein synthesis and the phenylpropanoid pathways, Phe can account for as much as~30% of the dry mass of a plant (Lewis & Yamamoto 1989;Margna, VainJarv & Laanest 1989;van Heerden, Towers & Lewis 1996). Little is known about the pathways responsible for the synthesis of Phe in plants and almost nothing about the regulation of the biosynthetic pathways or any regulatory roles that Phe itself might have in the actual initiation of stress responses.…”

Section: Introductionmentioning

confidence: 99%

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Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

Warpeha

Gibbons

Carol

et al. 2008

Plant Cell & Environment

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Etiolated Arabidopsis thaliana seedlings, lacking a functional prephenate dehydratase1 gene (PD1), also lack the ability to synthesize phenylalanine (Phe) and, as a consequence, phenylpropanoid pigments. We find that low doses of ultraviolet (UV)-C (254 nm) are lethal and low doses of UV-B cause severe damage to etiolated pd1 mutants, but not to wild-type (wt) seedlings. Furthermore, exposure to UV-C is lethal to etiolated gcr1 (encoding a putative G proteincoupled receptor in Arabidopsis) mutants and gpa1 (encoding the sole G protein a subunit in Arabidopsis) mutants. Addition of Phe to growth media restores wt levels of UV resistance to pd1 mutants. The data indicate that the Arabidopsis G protein-signalling pathway is critical to providing protection from UV, and does so via the activation of PD1, resulting in the synthesis of Phe. Cotyledons of etiolated pd1 mutants have proplastids (compared with etioplasts in wt), less cuticular wax and fewer long-chain fatty acids. Phederived pigments do not collect in the epidermal cells of pd1 mutants when seedlings are treated with UV, particularly at the cotyledon tip. Addition of Phe to the growth media restores a wt phenotype to pd1 mutants.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

Warpeha

Gibbons

Carol

et al. 2008

Plant Cell & Environment

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“…According to the carbon/nutrient balance hypothesis (Bryant et al 1983), on the other hand, both the type and amount of chemical defence will vary with the environmental availability of nutrients and on the basis of the carbon/nutrient balance in the plant tissue. The cornerstone for both hypotheses is the strong negative correlation between concentrations of plant nitrogen and phenolics, the trade‐off having a physiological basis in phenylalanine, a product of the shikimate acid pathway, which can be used either for protein or for phenolic synthesis (Margna 1977; Margna, Vainjärv & Laanast 1989).…”

Section: Introductionmentioning

confidence: 99%

Responses of Pinus sylvestris branches to simulated herbivory are modified by tree sink/source dynamics and by external resources

1999

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Responses of Pinus sylvestris branches to simulated herbivory are modified by tree sink/source dynamics and by external resources T. HONKANEN,* E. HAUKIOJA* and V. KITUNEN † *Laboratory of Ecological Zoology, Department of Biology, University of Turku, FIN-20014 Turku and †Finnish Forest Research Institute, P. O. Box 18, FIN-01301, Vantaa, Finland Summary 1. It is claimed that the quality of foliage following defoliation depends on carbon/nutrient balance of the tree. To study the importance of sink/source regulation for the quality of foliage, as well as for its quantity, Pinus sylvestris trees were defoliated and fertilized both in southern Finland and at the tree line in northern Finland. 2. The pattern of defoliation in a shoot was more decisive for quantitative changes in new foliage than its extent: removal of similar amounts of foliage from different branch parts led to different outcomes. 3. Defoliation of 50% spread evenly within a shoot, or applied to the basal part of a shoot only, did not alter production of new foliage, whereas defoliation applied to the apical part of a shoot decreased the mass and length of needles in the new shoot. Defoliation of apically located 1-year-old needles of the branch leader shoot, but not of 2-year-old ones, significantly reduced the mass and length of needles in new shoots. 4. These results are consistent with the explanation that damage alters the ability of shoots and branches to form strong meristematic sinks and that sink strength determines the ability of these meristems to draw resources from the common pool of the tree. 5. Defoliation of the main photosynthate source lowered concentrations of the fructose and glucose, indicating shortage of carbon. However, whole-tree defoliation did not affect the concentrations of individual foliar sugars. 6. Traits describing pine shoot growth correlated negatively with foliar phenolic concentrations but not with concentrations of other secondary compounds. Concentrations of foliage phenolics consistently increased after defoliation, while terpenoids, putatively the main class of defensive compounds in Scots Pine, did not respond to defoliation. Defoliation of a branch or a whole tree had only slight effects on the concentrations of fibre, mono-and sesquiterpenes, resin acids or nitrogen. 7. Likewise, fertilization significantly increased the concentration of some sesquiterpenes only in pine foliage. Whole-branch defoliation and fertilization together had no effect on the concentration of fibre or nitrogen in pine foliage. 8. Altogether, the amount of foliar biomass removed, nutrients or carbon did not explain in any consistent way the qualitative changes in the pine foliage. Instead, results were consistent with simple physiological dependence of foliar traits on sink strength. Production of terpenoids reflected increased sink strength, but the production of phenolics was negatively correlated with sink strength. 9. The difference between shoot growth characteristics and foliage concentrations of phenolics and, on the...

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“…Flavonoids and other UV-screening pigments are found in seeds, which vary with regard to both composition and concentration among different plant species [14] . The rate-limiting step in general for phenylpropanoids is the synthesis or availability of Phe [15] – [17] . In seedlings of Arabidopsis thaliana , it was demonstrated that Phe supply was important to survival against UV-C, and in pigment synthesis after exposure to UV-A and UV-B wavelengths [3] .…”

Section: Introductionmentioning

confidence: 99%

Phenylalanine Is Required to Promote Specific Developmental Responses and Prevents Cellular Damage in Response to Ultraviolet Light in Soybean (Glycine max) during the Seed-to-Seedling Transition

2014

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UV-radiation elicits a suite of developmental (photomorphogenic) and protective responses in plants, but responses early post-germination have received little attention, particularly in intensively bred plants of economic importance. We examined germination, hypocotyl elongation, leaf pubescence and subcellular responses of germinating and/or etiolated soybean (Glycine max (L.) Merr.) seedlings in response to treatment with discrete wavelengths of UV-A or UV-B radiation. We demonstrate differential responses of germinating/young soybean seedlings to a range of UV wavelengths that indicate unique signal transduction mechanisms regulate UV-initiated responses. We have investigated how phenylalanine, a key substrate in the phenylpropanoid pathway, may be involved in these responses. Pubescence may be a key location for phenylalanine-derived protective compounds, as UV-B irradiation increased pubescence and accumulation of UV-absorbing compounds within primary leaf pubescence, visualized by microscopy and absorbance spectra. Mass spectrometry analysis of pubescence indicated that sinapic esters accumulate in the UV-irradiated hairs compared to unirradiated primary leaf tissue. Deleterious effects of some UV-B wavelengths on germination and seedling responses were reduced or entirely prevented by inclusion of phenylalanine in the growth media. Key effects of phenylalanine were not duplicated by tyrosine or tryptophan or sucrose, nor is the specificity of response due to the absorbance of phenylalanine itself. These results suggest that in the seed-to-seedling transition, phenylalanine may be a limiting factor in the development of initial mechanisms of UV protection in the developing leaf.

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Different l-phenylalanine pools available for the biosynthesis of phenolics in buckwheat seedling tissues

Cited by 18 publications

References 19 publications

Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

Adequate phenylalanine synthesis mediated by G protein is critical for protection from UV radiation damage in young etiolated Arabidopsis thaliana seedlings

Responses of Pinus sylvestris branches to simulated herbivory are modified by tree sink/source dynamics and by external resources

Phenylalanine Is Required to Promote Specific Developmental Responses and Prevents Cellular Damage in Response to Ultraviolet Light in Soybean (Glycine max) during the Seed-to-Seedling Transition

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