Wound-Inducible Biosynthesis of Phytoalexin Hydroxycinnamic Acid Amides of Tyramine in Tryptophan and Tyrosine Decarboxylase Transgenic Tobacco Lines

Abstract

The wound-activated biosynthesis of phytoalexin hydroxycinnamic acid amides of tyramine was compared in untransformed and transgenic tobacco (Nicotiana tabacum) lines that express tryptophan decarboxylase (TDC), tyrosine decarboxylase (TYDC), or both activities. Transgenic in vitro-grown tobacco lines expressing TDC activity accumulated high levels of tryptamine but not hydroxycinnamic amides of tryptamine. In contrast, transgenic tobacco lines expressing TYDC accumulated tyramine as well as p-coumaroyltyramine and feruloyltyramine. The MeOH-soluble and cell wall fractions showed higher concentrations of wound-inducible p-coumaroyltyramine and feruloyltyramine, especially at and around wound sites, in TYDC and TDC 3 TYDC tobacco lines compared to wild-type or TDC lines. All the enzymes involved in the biosynthesis of hydroxycinnamic acid amides of tyramine were found to be similarly wound inducible in all tobacco genotypes investigated. These results provide experimental evidence that, under some circumstances, TYDC activity can exert a rate-limiting control over the carbon flux allocated to the biosynthesis of hydroxycinnamic acid amides of tyramine.The importance of tyramine during suberization of wounded potato (Solanum tuberosum) tubers is well established. Borg-Olivier and Monties (1993) used alkaline hydrolysis to fractionate and characterize the MeOH-extractable components of wound periderm in healing potato tuber discs. Fourteen days postwounding, their results established that tyramine accounts for 23% of total phenylpropanoids and Tyr-derived metabolites occurring in the MeOH-extractable free residue, whereas tyramine was undetected in the control nonwounded potato tuber discs. The presence of tyramine in suberizing potato periderm has also been corroborated by in situ noninvasive solid-state 13 C-NMR spectroscopy that allows the characterization of the polyaromatic domain of suberin in its native state within the plant cell wall matrix (Bernards et al., 1995;Bernards and Lewis, 1998).Phytoalexin hydroxycinnamic acid amides of tyramine (PCAAT), which are formed by the conjugation of tyramine with cinnamoyl-CoA thioesters (Negrel and Javelle, 1997), represent a major class of tyraminederived metabolites. The biosynthesis of PCAAT is elicited by wounding (Pearce et al., 1998;Ishihara et al., 2000) or pathogen inoculation (Keller et al., 1996;Muhlenbeck et al., 1996;Schmidt et al., 1998;Newman et al., 2001) in many species (Martin-Tanguy et al., 1996), especially in solanaceous plants (Clarke, 1982;Keller et al., 1996;Muhlenbeck et al., 1996). PCAAT can be further integrated into cell walls via a peroxidase-mediated process (Negrel and Lherminier, 1987;Keller et al., 1996) that yields monoor dicovalent ether bonds between cinnamoyl or tyramine moieties of PCAAT and the plant phenolic cell wall matrix (Lapierre et al., 1996). Although some PCAAT possess cytotoxic properties (Yamamoto et al., 1991;Park and Schoene, 2002), it is generally speculated that their major function in plants is to reinforce cell wa...

Novel Roles for the Polyphenol Oxidase Enzyme in Secondary Metabolism and the Regulation of Cell Death in Walnut

“…For example, the accumulation of HCAAs is typically associated with wounding, pathogen challenge, or other stressors (Facchini et al, 2002;Guillet and De Luca, 2005). Thus, the observed accumulation of HCAAs around necrotic lesions in the PPO-silenced walnut lines (Fig.…”

“…The accumulation of aromatic amines such as tyramine, tryptamine, and serotonin is often associated with the synthesis of hydroxycinnamic acid amides (HCAAs), which are deposited into the cell wall, increasing its strength and reducing its digestibility (Jang et al, 2004;Ishihara et al, 2008). HCAAs are produced through the condensation of aromatic amines and hydroxycinnamoylCoA thioesters, often in response to wounding or pathogen challenge (Guillet and De Luca, 2005;Muroi et al, 2009). Because both aromatic amines and phenylpropanoidderived hydroxycinnamoyl-CoA thioesters are presumably elevated in PPO-silenced lines, we examined HCAA accumulation in situ by staining walnut leaf sections with Neu's reagent and visualizing HCAA fluorescence (Alemanno et al, 2003).…”

Chemistry and evolution of the Piperaceae

“…Dopamine is not common as a natural product, but has been previously identified in P. amalago [4], and both phenylethylamines have been found in plants as cinnamoyl conjugates in Piper species [54,55] and as N-benzoyltyramine in Aniba riparia [56]. The physiological role of tyramine amides as phytoalexins has been recognized in tobacco, Nicotiana tabacum [57], and they have also been shown to be directly involved in suberization processes in wounded potatoes (Solanum tuberosum) [58]. The only indication of a regulatory role for such compounds in suspension cells of P. crassinervium is the finding that alkamide production is induced by UV light (unpublished results).…”

The effect of a mealybug infestation on the activity of amino acid decarboxylases in orchid leaves

“…A biochemical plant defense may be elicited by components of aphids' saliva and/or wounding of epidermal, mesophyll, and parenchyma cells during their probing behavior (Goggin 2007;Giordanengo et al 2010). Mechanical wounding of transgenic tobacco induced activity of TyDC and tryptophan decarboxylase, and increased the tyramine, ferloyltyramine, and 4-coumaroyltyramine levels (Guillet & De Luca 2005;Hagel & Facchini 2005). Moreover, systemic plant responses induced by aphid and other hemipterous insects may be signalized by jasmonic acid (JA), salicylic acid, ethylene, abscisic acid (ABA), and gibberellic acid (Morkunas et al 2011;Takemoto et al 2013).…”