Growth-promoting nitrogen nutrition affects flavonoid biosynthesis in young apple (Malus domestica Borkh.) leaves |
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Authors: | Strissel T Halbwirth H Hoyer U Zistler C Stich K Treutter D |
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Institution: | Department für Pflanzenwissenschaften, Fachgebiet Obstbau, Technische Universit?t München-Weihenstephan, Alte Akademie 16, 85350 Freising, Germany. |
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Abstract: | Enhanced shoot growth and a decrease in flavonoid concentration in apple trees grown under high nitrogen (N) supply was observed in previous studies, along with increasing scab susceptibility of cultivar "Golden Delicious" after high N nutrition. Several hypotheses have suggested that there is a trade-off between primary and secondary metabolism because of competition for common substrates, but nothing is known about regulation at the enzyme level. In this study, a set of experiments was performed to elucidate the effect of N nutrition on the activities of key enzymes involved in flavonoid biosynthesis (phenylalanine ammonia-lyase PAL], chalcone synthase/chalcone isomerase CHS/CHI}, flavanone 3-hydroxylase FHT], flavonol synthase FLS], dihydroflavonol 4-reductase DFR]) and the accumulation of different groups of phenylpropanoids. The inhibition of flavonoid accumulation by high N nutrition could be confirmed, but the influence of N supply on the flavonoid enzymes CHS/CHI, FHT, DFR, and FLS was not evident. However, PAL activity seems to be downregulated, thus forming a bottleneck resulting in a generally decreased flavonoid accumulation. Furthermore, the response of the scab-resistant cultivar "Rewena" to high N nutrition was not as strong as that of the susceptible cultivar "Golden Delicious". |
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Keywords: | Phenylalanine ammonia-lyase (PAL) chalcone synthase/chalcone isomerase (CHS/CHI) flavanone 3-hydroxylase (FHT) flavonol synthase (FLS) dihydroflavonol 4-reductase (DFR) nitrogen nutrition apple leaf hydroxycinnamic acids dihydrochalcones flavonols flavanols |
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