Phenylpropanoid biosynthesis in plants

Results of Wulf et al (7) show that carrot roots obtained from a supermarket contain myristicin Imperator variety carrots contain an average of 15 parts per million (ppm). Recently harvested, unprocessed carrots only rarely contain myristicin (8). The presence of myristicin in supermarket carrots and its absence in recently harvested ones indicate that its increased concentration may have been induced by some elicitor following harvest. Solar radiation after harvest, or fluorescent lighting during display, may function as such an elicitor. Light is known to produce ethylene and is an activator of phenylalanine ammonia-lyase, one of the regulatory enzymes responsible for phenylpropanoid biosynthesis in plants (9). 

Phenylpropanoid Biosynthesis in Plants Enzymology and Pathway Topology 491 Transcriptional and Posttranscriptional Regulation of Phenylpropanoid Biosynthesis in Plants 504... 

Phenylpropanoid Biosynthesis in Plants Enzymology and Pathway Topology... 

Transcriptional and Posttranscriptional Regulation of Phenylpropanoid Biosynthesis in Plants... 

SCHEME 2.4 Type III PKS involved in phenylpropanoid biosynthesis in plants. 

In either of the proposed pathways, salicylic acid is synthesised from tram-cinnamic acid. This is an intriguing observation and may provide a clue as to how and why the induction of SAR is tightly linked to the formation of a necrotic lesion. When plants react hypersensitively to pathogen attack, many biochemical changes occur, including the induction of phenylpropanoid biosynthesis. In bean, as well as other plants, this induction seems to be at least partly caused by an increase in the synthesis of phenylalanine ammonium lyase and other enzymes involved in the biosynthesis of isoflavonoid phytoalexins, flavonoid pigments and... 

Comino, C., Lanteri, S., Portis, E., Acquadro, A., Romani, A., Hehn, A., Larbat, R. and Bourgaud, R (2007) Isolation and functional characterization of a cDNA coding a hydroxycinnamoyltransferase involved in phenylpropanoid biosynthesis in Cynara cardunculus L. BMC Plant Biol, 7. 

Plant metabolism can be separated into primary pathways that are found in all cells and deal with manipulating a uniform group of basic compounds, and secondary pathways that occur in specialized cells and produce a wide variety of unique compounds. The primary pathways deal with the metabolism of carbohydrates, lipids, proteins, and nucleic acids and act through the many-step reactions of glycolysis, the tricarboxylic acid cycle, the pentose phosphate shunt, and lipid, protein, and nucleic acid biosynthesis. In contrast, the secondary metabolites (e.g., terpenes, alkaloids, phenylpropanoids, lignin, flavonoids, coumarins, and related compounds) are produced by the shikimic, malonic, and mevalonic acid pathways, and the methylerythritol phosphate pathway (Fig. 3.1). This chapter concentrates on the synthesis and metabolism of phenolic compounds and on how the activities of these pathways and the compounds produced affect product quality. 

Figure 1. Phenylalanine ammonia-lyase (PAL) involvement in the biosynthesis of phenylpropanoid-derived secondary metabolites in plants and Ba-sidiomycetes.

Tamagnone, L. et al.. The AmMYB308 and AmMYB330 transcription factors from Antirrhinum regulate phenylpropanoid and lignin biosynthesis in transgenic tobacco. Plant Cell, 10, 135, 1998. 

Funk C, Brodelius P (1992) Phenylpropanoid metabolism in suspension cultures of Vanilla planifolia Andr. IV Induction of vanillinic acid formation. Plant Physiol 99 256-262 Funk C, Brodelius P (1994) Vanilla planifolia Andrews in vitro biosynthesis of vanillin and other phenylpropanoids derivatives. In Bajaj YPS (ed) Biotechnology in agriculture and forestry. Medicinal and aromatic plants VI, vol 26. Springer, Berlin Heidelberg New York, pp 377-402... 

Chappie, . C. S. and . E. Ellis. 1991. Syringa vulgaris L. (common lilac) in vitro culture and the occurrence and biosynthesis of phenylpropanoid glycosides. In Bajaj, Y. P. S. (ed.). Biotechnology in Agriculture and Forestry 15. Medicinal and Aromatic Plants III. Springer-Verlag. New York. p. 478-497. 

Table 21.1 Plant Transcription Factors Involved in Phenylpropanoid Biosynthesis Regulation and Their Known Regulons...

In plants, biosynthesis and exudation of allelochemicals follows developmental, diurnal, and abiotic/biotic stress-dependent dynamics. Compounds from 14 different chemical classes have been linked to allelopathic interactions, including several simple phenolic acids (e.g., benzoic and hydroxycinnamic acids) and flavonoids [Rice, 1984 Macias et al., 2007]. The existence of several soil biophysical processes that can reduce the effective concentration and bioactivity of these compounds casts doubts on their actual relevance in allelopathic interactions [Olofsdotter et al., 2002]. However, there are well-documented examples of phenylpropanoid-mediated incompatible interactions among plants. Several Gramineae mediate allelopathic interactions by means of... 

Achnine L, Blancaflor EB, Rasmussen S, Dixon RA. 2004. Colocalization of L-phenylalanine ammonia-lyase and cinnamate 4-hydroxylase for metabolic channeling in phenylpropanoid biosynthesis. Plant Cell 16 3098-3109. 

Dixon RA, Choundhary AD, Dalkin K, Edwards R, Fahrendorf T, Gowni G, Harrison MJ, Lamb CJ, Loake GJ, Maxwell CA, Orr J, Paiva NL. 1992. Molecular biology of stress-induced phenylpropanoid and isoflavonoid biosynthesis in alfalfa. In Stafford HA, Ibrahim RK, Eds. Phenolic Metabolism in Plants. New York Plenum, pp. 91-138. 

Farag MA, Huhman DV, Dixon RA, Sumner LW. 2008. Metabolomics reveals novel pathways and differential mechanistic and elicitor-specific responses in phenylpropanoid and isoflavonoid biosynthesis in Medicago truncatula cell cultures. Plant Physiol 146 387 402. 

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