ABSTRACT

Phenylpropanoid compounds are widely used by plants as a part of the 
antimicrobial defense arsenal. A number of these products have been implicated in 
disease resistance playing different roles: signaling (salicylic acid), antimicrobials, and 
plant cell wall reinforcement. Among them, hydroxycinnamic acid amides (HCAA) 
constitute an important group that has been implicated in the plant defense to both 
pathogens and insect attack. HCCA are formed by the condensation of 
hydroxycinnamoy-CoA thioesters with phenylethylamines such as tyramine. The last 
step in tyramine-derived HCAA biosynthesis is catalized by hydroxycinnamoyl-
CoA:tyramine N-(hydroxycinnamoyl) transferase (THT).

Here we report the identification and characterization of four HCAA, p-
coumaroyldopamine, feruloyldopamine, p-coumaroyltyramine and feruloyltyramine, 
induced in tomato plants upon Pseudomonas syringae pv. tomato infection. Their 
identification and structural characterization have been made by MS-HPLC techniques. 
We also have explored the implication of ethylene and salicylic acid on HCAA 
accumulation. Antimicrobial and antioxidant in vitro studies have been performed using 
the four synthesized amides. Additionally, we have obtained transgenic Arabidopsis 
thaliana and tomato lines overexpressing THT. Changes in the metabolic profile of the 
overexpressing THT lines compared with wild-type are analyzed.