Functional characterization of a small gene family coding for putrescine hydroxycinnamoyltransferases in tomato

Phenolamides are specialized metabolites widely distributed in the plant kingdom. Their structure is composed by the association of hydroxycinnamic acid derivatives to mono-/poly-amine. This association is catalyzed by N-hydroxycinnamoyltransferases enzymes. Tomato plants are accumulating putrescine-derived phenolamides in their vegetative parts. Recently, we identified two genes coding for putrescine-hydroxycinnamoyltransferase (PHT, Solyc11g071470 and Solyc11g071480), which control the accumulation of caffeoylputrescine in tomato leaf submitted to the infestation of leafminer. In this study, we prospected for additional genes implicated in the accumulation of putrescine-derived phenolamides in the tomato vegetative organs. We identified two genes (Solyc06g074710 and Solyc11g066640) that we functionally characterized as new PHT. The substrate specificity and the expression pattern in planta was determined for the four tomato PHT. Taken together the results give a comprehensive view of the control of the putrescine-derived phenolamide accumulation in tomato plant through the biochemical specificity and the spatial expression of this small family of PHT. Main conclusion We identified and functionally characterized two new putrescine hydroxycinnamoyl transferases (PHT) in tomato. These enzymes complete a set a four PHT which control the distribution of putrescine-derived phenolamides in tomato plants.